// SPDX-License-Identifier: GPL-2.0+
/*
* SSH request transport layer.
*
* Copyright (C) 2019-2022 Maximilian Luz <[email protected]>
*/
#include <linux/unaligned.h>
#include <linux/atomic.h>
#include <linux/completion.h>
#include <linux/error-injection.h>
#include <linux/ktime.h>
#include <linux/limits.h>
#include <linux/list.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/types.h>
#include <linux/workqueue.h>
#include <linux/surface_aggregator/serial_hub.h>
#include <linux/surface_aggregator/controller.h>
#include "ssh_packet_layer.h"
#include "ssh_request_layer.h"
#include "trace.h"
/*
* SSH_RTL_REQUEST_TIMEOUT - Request timeout.
*
* Timeout as ktime_t delta for request responses. If we have not received a
* response in this time-frame after finishing the underlying packet
* transmission, the request will be completed with %-ETIMEDOUT as status
* code.
*/
#define SSH_RTL_REQUEST_TIMEOUT ms_to_ktime(3000)
/*
* SSH_RTL_REQUEST_TIMEOUT_RESOLUTION - Request timeout granularity.
*
* Time-resolution for timeouts. Should be larger than one jiffy to avoid
* direct re-scheduling of reaper work_struct.
*/
#define SSH_RTL_REQUEST_TIMEOUT_RESOLUTION ms_to_ktime(max(2000 / HZ, 50))
/*
* SSH_RTL_MAX_PENDING - Maximum number of pending requests.
*
* Maximum number of requests concurrently waiting to be completed (i.e.
* waiting for the corresponding packet transmission to finish if they don't
* have a response or waiting for a response if they have one).
*/
#define SSH_RTL_MAX_PENDING 3
/*
* SSH_RTL_TX_BATCH - Maximum number of requests processed per work execution.
* Used to prevent livelocking of the workqueue. Value chosen via educated
* guess, may be adjusted.
*/
#define SSH_RTL_TX_BATCH 10
#ifdef CONFIG_SURFACE_AGGREGATOR_ERROR_INJECTION
/**
* ssh_rtl_should_drop_response() - Error injection hook to drop request
* responses.
*
* Useful to cause request transmission timeouts in the driver by dropping the
* response to a request.
*/
static noinline bool ssh_rtl_should_drop_response(void)
{
return false;
}
ALLOW_ERROR_INJECTION(ssh_rtl_should_drop_response, TRUE);
#else
static inline bool ssh_rtl_should_drop_response(void)
{
return false;
}
#endif
static u16 ssh_request_get_rqid(struct ssh_request *rqst)
{
return get_unaligned_le16(rqst->packet.data.ptr
+ SSH_MSGOFFSET_COMMAND(rqid));
}
static u32 ssh_request_get_rqid_safe(struct ssh_request *rqst)
{
if (!rqst->packet.data.ptr)
return U32_MAX;
return ssh_request_get_rqid(rqst);
}
static void ssh_rtl_queue_remove(struct ssh_request *rqst)
{
struct ssh_rtl *rtl = ssh_request_rtl(rqst);
spin_lock(&rtl->queue.lock);
if (!test_and_clear_bit(SSH_REQUEST_SF_QUEUED_BIT, &rqst->state)) {
spin_unlock(&rtl->queue.lock);
return;
}
list_del(&rqst->node);
spin_unlock(&rtl->queue.lock);
ssh_request_put(rqst);
}
static bool ssh_rtl_queue_empty(struct ssh_rtl *rtl)
{
bool empty;
spin_lock(&rtl->queue.lock);
empty = list_empty(&rtl->queue.head);
spin_unlock(&rtl->queue.lock);
return empty;
}
static void ssh_rtl_pending_remove(struct ssh_request *rqst)
{
struct ssh_rtl *rtl = ssh_request_rtl(rqst);
spin_lock(&rtl->pending.lock);
if (!test_and_clear_bit(SSH_REQUEST_SF_PENDING_BIT, &rqst->state)) {
spin_unlock(&rtl->pending.lock);
return;
}
atomic_dec(&rtl->pending.count);
list_del(&rqst->node);
spin_unlock(&rtl->pending.lock);
ssh_request_put(rqst);
}
static int ssh_rtl_tx_pending_push(struct ssh_request *rqst)
{
struct ssh_rtl *rtl = ssh_request_rtl(rqst);
spin_lock(&rtl->pending.lock);
if (test_bit(SSH_REQUEST_SF_LOCKED_BIT, &rqst->state)) {
spin_unlock(&rtl->pending.lock);
return -EINVAL;
}
if (test_and_set_bit(SSH_REQUEST_SF_PENDING_BIT, &rqst->state)) {
spin_unlock(&rtl->pending.lock);
return -EALREADY;
}
atomic_inc(&rtl->pending.count);
list_add_tail(&ssh_request_get(rqst)->node, &rtl->pending.head);
spin_unlock(&rtl->pending.lock);
return 0;
}
static void ssh_rtl_complete_with_status(struct ssh_request *rqst, int status)
{
struct ssh_rtl *rtl = ssh_request_rtl(rqst);
trace_ssam_request_complete(rqst, status);
/* rtl/ptl may not be set if we're canceling before submitting. */
rtl_dbg_cond(rtl, "rtl: completing request (rqid: %#06x, status: %d)\n",
ssh_request_get_rqid_safe(rqst), status);
rqst->ops->complete(rqst, NULL, NULL, status);
}
static void ssh_rtl_complete_with_rsp(struct ssh_request *rqst,
const struct ssh_command *cmd,
const struct ssam_span *data)
{
struct ssh_rtl *rtl = ssh_request_rtl(rqst);
trace_ssam_request_complete(rqst, 0);
rtl_dbg(rtl, "rtl: completing request with response (rqid: %#06x)\n",
ssh_request_get_rqid(rqst));
rqst->ops->complete(rqst, cmd, data, 0);
}
static bool ssh_rtl_tx_can_process(struct ssh_request *rqst)
{
struct ssh_rtl *rtl = ssh_request_rtl(rqst);
if (test_bit(SSH_REQUEST_TY_FLUSH_BIT, &rqst->state))
return !atomic_read(&rtl->pending.count);
return atomic_read(&rtl->pending.count) < SSH_RTL_MAX_PENDING;
}
static struct ssh_request *ssh_rtl_tx_next(struct ssh_rtl *rtl)
{
struct ssh_request *rqst = ERR_PTR(-ENOENT);
struct ssh_request *p, *n;
spin_lock(&rtl->queue.lock);
/* Find first non-locked request and remove it. */
list_for_each_entry_safe(p, n, &rtl->queue.head, node) {
if (unlikely(test_bit(SSH_REQUEST_SF_LOCKED_BIT, &p->state)))
continue;
if (!ssh_rtl_tx_can_process(p)) {
rqst = ERR_PTR(-EBUSY);
break;
}
/* Remove from queue and mark as transmitting. */
set_bit(SSH_REQUEST_SF_TRANSMITTING_BIT, &p->state);
/* Ensure state never gets zero. */
smp_mb__before_atomic();
clear_bit(SSH_REQUEST_SF_QUEUED_BIT, &p->state);
list_del(&p->node);
rqst = p;
break;
}
spin_unlock(&rtl->queue.lock);
return rqst;
}
static int ssh_rtl_tx_try_process_one(struct ssh_rtl *rtl)
{
struct ssh_request *rqst;
int status;
/* Get and prepare next request for transmit. */
rqst = ssh_rtl_tx_next(rtl);
if (IS_ERR(rqst))
return PTR_ERR(rqst);
/* Add it to/mark it as pending. */
status = ssh_rtl_tx_pending_push(rqst);
if (status) {
ssh_request_put(rqst);
return -EAGAIN;
}
/* Submit packet. */
status = ssh_ptl_submit(&rtl->ptl, &rqst->packet);
if (status == -ESHUTDOWN) {
/*
* Packet has been refused due to the packet layer shutting
* down. Complete it here.
*/
set_bit(SSH_REQUEST_SF_LOCKED_BIT, &rqst->state);
/*
* Note: A barrier is not required here, as there are only two
* references in the system at this point: The one that we have,
* and the other one that belongs to the pending set. Due to the
* request being marked as "transmitting", our process is the
* only one allowed to remove the pending node and change the
* state. Normally, the task would fall to the packet callback,
* but as this is a path where submission failed, this callback
* will never be executed.
*/
ssh_rtl_pending_remove(rqst);
ssh_rtl_complete_with_status(rqst, -ESHUTDOWN);
ssh_request_put(rqst);
return -ESHUTDOWN;
} else if (status) {
/*
* If submitting the packet failed and the packet layer isn't
* shutting down, the packet has either been submitted/queued
* before (-EALREADY, which cannot happen as we have
* guaranteed that requests cannot be re-submitted), or the
* packet was marked as locked (-EINVAL). To mark the packet
* locked at this stage, the request, and thus the packets
* itself, had to have been canceled. Simply drop the
* reference. Cancellation itself will remove it from the set
* of pending requests.
*/
WARN_ON(status != -EINVAL);
ssh_request_put(rqst);
return -EAGAIN;
}
ssh_request_put(rqst);
return 0;
}
static bool ssh_rtl_tx_schedule(struct ssh_rtl *rtl)
{
if (atomic_read(&rtl->pending.count) >= SSH_RTL_MAX_PENDING)
return false;
if (ssh_rtl_queue_empty(rtl))
return false;
return schedule_work(&rtl->tx.work);
}
static void ssh_rtl_tx_work_fn(struct work_struct *work)
{
struct ssh_rtl *rtl = to_ssh_rtl(work, tx.work);
unsigned int iterations = SSH_RTL_TX_BATCH;
int status;
/*
* Try to be nice and not block/live-lock the workqueue: Run a maximum
* of 10 tries, then re-submit if necessary. This should not be
* necessary for normal execution, but guarantee it anyway.
*/
do {
status = ssh_rtl_tx_try_process_one(rtl);
if (status == -ENOENT || status == -EBUSY)
return; /* No more requests to process. */
if (status == -ESHUTDOWN) {
/*
* Packet system shutting down. No new packets can be
* transmitted. Return silently, the party initiating
* the shutdown should handle the rest.
*/
return;
}
WARN_ON(status != 0 && status != -EAGAIN);
} while (--iterations);
/* Out of tries, reschedule. */
ssh_rtl_tx_schedule(rtl);
}
/**
* ssh_rtl_submit() - Submit a request to the transport layer.
* @rtl: The request transport layer.
* @rqst: The request to submit.
*
* Submits a request to the transport layer. A single request may not be
* submitted multiple times without reinitializing it.
*
* Return: Returns zero on success, %-EINVAL if the request type is invalid or
* the request has been canceled prior to submission, %-EALREADY if the
* request has already been submitted, or %-ESHUTDOWN in case the request
* transport layer has been shut down.
*/
int ssh_rtl_submit(struct ssh_rtl *rtl, struct ssh_request *rqst)
{
trace_ssam_request_submit(rqst);
/*
* Ensure that requests expecting a response are sequenced. If this
* invariant ever changes, see the comment in ssh_rtl_complete() on what
* is required to be changed in the code.
*/
if (test_bit(SSH_REQUEST_TY_HAS_RESPONSE_BIT, &rqst->state))
if (!test_bit(SSH_PACKET_TY_SEQUENCED_BIT, &rqst->packet.state))
return -EINVAL;
spin_lock(&rtl->queue.lock);
/*
* Try to set ptl and check if this request has already been submitted.
*
* Must be inside lock as we might run into a lost update problem
* otherwise: If this were outside of the lock, cancellation in
* ssh_rtl_cancel_nonpending() may run after we've set the ptl
* reference but before we enter the lock. In that case, we'd detect
* that the request is being added to the queue and would try to remove
* it from that, but removal might fail because it hasn't actually been
* added yet. By putting this cmpxchg in the critical section, we
* ensure that the queuing detection only triggers when we are already
* in the critical section and the remove process will wait until the
* push operation has been completed (via lock) due to that. Only then,
* we can safely try to remove it.
*/
if (cmpxchg(&rqst->packet.ptl, NULL, &rtl->ptl)) {
spin_unlock(&rtl->queue.lock);
return -EALREADY;
}
/*
* Ensure that we set ptl reference before we continue modifying state.
* This is required for non-pending cancellation. This barrier is paired
* with the one in ssh_rtl_cancel_nonpending().
*
* By setting the ptl reference before we test for "locked", we can
* check if the "locked" test may have already run. See comments in
* ssh_rtl_cancel_nonpending() for more detail.
*/
smp_mb__after_atomic();
if (test_bit(SSH_RTL_SF_SHUTDOWN_BIT, &rtl->state)) {
spin_unlock(&rtl->queue.lock);
return -ESHUTDOWN;
}
if (test_bit(SSH_REQUEST_SF_LOCKED_BIT, &rqst->state)) {
spin_unlock(&rtl->queue.lock);
return -EINVAL;
}
set_bit(SSH_REQUEST_SF_QUEUED_BIT, &rqst->state);
list_add_tail(&ssh_request_get(rqst)->node, &rtl->queue.head);
spin_unlock(&rtl->queue.lock);
ssh_rtl_tx_schedule(rtl);
return 0;
}
static void ssh_rtl_timeout_reaper_mod(struct ssh_rtl *rtl, ktime_t now,
ktime_t expires)
{
unsigned long delta = msecs_to_jiffies(ktime_ms_delta(expires, now));
ktime_t aexp = ktime_add(expires, SSH_RTL_REQUEST_TIMEOUT_RESOLUTION);
spin_lock(&rtl->rtx_timeout.lock);
/* Re-adjust / schedule reaper only if it is above resolution delta. */
if (ktime_before(aexp, rtl->rtx_timeout.expires)) {
rtl->rtx_timeout.expires = expires;
mod_delayed_work(system_wq, &rtl->rtx_timeout.reaper, delta);
}
spin_unlock(&rtl->rtx_timeout.lock);
}
static void ssh_rtl_timeout_start(struct ssh_request *rqst)
{
struct ssh_rtl *rtl = ssh_request_rtl(rqst);
ktime_t timestamp = ktime_get_coarse_boottime();
ktime_t timeout = rtl->rtx_timeout.timeout;
if (test_bit(SSH_REQUEST_SF_LOCKED_BIT, &rqst->state))
return;
/*
* Note: The timestamp gets set only once. This happens on the packet
* callback. All other access to it is read-only.
*/
WRITE_ONCE(rqst->timestamp, timestamp);
/*
* Ensure timestamp is set before starting the reaper. Paired with
* implicit barrier following check on ssh_request_get_expiration() in
* ssh_rtl_timeout_reap.
*/
smp_mb__after_atomic();
ssh_rtl_timeout_reaper_mod(rtl, timestamp, timestamp + timeout);
}
static void ssh_rtl_complete(struct ssh_rtl *rtl,
const struct ssh_command *command,
const struct ssam_span *command_data)
{
struct ssh_request *r = NULL;
struct ssh_request *p, *n;
u16 rqid = get_unaligned_le16(&command->rqid);
trace_ssam_rx_response_received(command, command_data->len);
/*
* Get request from pending based on request ID and mark it as response
* received and locked.
*/
spin_lock(&rtl->pending.lock);
list_for_each_entry_safe(p, n, &rtl->pending.head, node) {
/* We generally expect requests to be processed in order. */
if (unlikely(ssh_request_get_rqid(p) != rqid))
continue;
/* Simulate response timeout. */
if (ssh_rtl_should_drop_response()) {
spin_unlock(&rtl->pending.lock);
trace_ssam_ei_rx_drop_response(p);
rtl_info(rtl, "request error injection: dropping response for request %p\n",
&p->packet);
return;
}
/*
* Mark as "response received" and "locked" as we're going to
* complete it.
*/
set_bit(SSH_REQUEST_SF_LOCKED_BIT, &p->state);
set_bit(SSH_REQUEST_SF_RSPRCVD_BIT, &p->state);
/* Ensure state never gets zero. */
smp_mb__before_atomic();
clear_bit(SSH_REQUEST_SF_PENDING_BIT, &p->state);
atomic_dec(&rtl->pending.count);
list_del(&p->node);
r = p;
break;
}
spin_unlock(&rtl->pending.lock);
if (!r) {
rtl_warn(rtl, "rtl: dropping unexpected command message (rqid = %#06x)\n",
rqid);
return;
}
/* If the request hasn't been completed yet, we will do this now. */
if (test_and_set_bit(SSH_REQUEST_SF_COMPLETED_BIT, &r->state)) {
ssh_request_put(r);
ssh_rtl_tx_schedule(rtl);
return;
}
/*
* Make sure the request has been transmitted. In case of a sequenced
* request, we are guaranteed that the completion callback will run on
* the receiver thread directly when the ACK for the packet has been
* received. Similarly, this function is guaranteed to run on the
* receiver thread. Thus we are guaranteed that if the packet has been
* successfully transmitted and received an ACK, the transmitted flag
* has been set and is visible here.
*
* We are currently not handling unsequenced packets here, as those
* should never expect a response as ensured in ssh_rtl_submit. If this
* ever changes, one would have to test for
*
* (r->state & (transmitting | transmitted))
*
* on unsequenced packets to determine if they could have been
* transmitted. There are no synchronization guarantees as in the
* sequenced case, since, in this case, the callback function will not
* run on the same thread. Thus an exact determination is impossible.
*/
if (!test_bit(SSH_REQUEST_SF_TRANSMITTED_BIT, &r->state)) {
rtl_err(rtl, "rtl: received response before ACK for request (rqid = %#06x)\n",
rqid);
/*
* NB: Timeout has already been canceled, request already been
* removed from pending and marked as locked and completed. As
* we receive a "false" response, the packet might still be
* queued though.
*/
ssh_rtl_queue_remove(r);
ssh_rtl_complete_with_status(r, -EREMOTEIO);
ssh_request_put(r);
ssh_rtl_tx_schedule(rtl);
return;
}
/*
* NB: Timeout has already been canceled, request already been
* removed from pending and marked as locked and completed. The request
* can also not be queued any more, as it has been marked as
* transmitting and later transmitted. Thus no need to remove it from
* anywhere.
*/
ssh_rtl_complete_with_rsp(r, command, command_data);
ssh_request_put(r);
ssh_rtl_tx_schedule(rtl);
}
static bool ssh_rtl_cancel_nonpending(struct ssh_request *r)
{
struct ssh_rtl *rtl;
unsigned long flags, fixed;
bool remove;
/*
* Handle unsubmitted request: Try to mark the packet as locked,
* expecting the state to be zero (i.e. unsubmitted). Note that, if
* setting the state worked, we might still be adding the packet to the
* queue in a currently executing submit call. In that case, however,
* ptl reference must have been set previously, as locked is checked
* after setting ptl. Furthermore, when the ptl reference is set, the
* submission process is guaranteed to have entered the critical
* section. Thus only if we successfully locked this request and ptl is
* NULL, we have successfully removed the request, i.e. we are
* guaranteed that, due to the "locked" check in ssh_rtl_submit(), the
* packet will never be added. Otherwise, we need to try and grab it
* from the queue, where we are now guaranteed that the packet is or has
* been due to the critical section.
*
* Note that if the cmpxchg() fails, we are guaranteed that ptl has
* been set and is non-NULL, as states can only be nonzero after this
* has been set. Also note that we need to fetch the static (type)
* flags to ensure that they don't cause the cmpxchg() to fail.
*/
fixed = READ_ONCE(r->state) & SSH_REQUEST_FLAGS_TY_MASK;
flags = cmpxchg(&r->state, fixed, SSH_REQUEST_SF_LOCKED_BIT);
/*
* Force correct ordering with regards to state and ptl reference access
* to safe-guard cancellation to concurrent submission against a
* lost-update problem. First try to exchange state, then also check
* ptl if that worked. This barrier is paired with the
* one in ssh_rtl_submit().
*/
smp_mb__after_atomic();
if (flags == fixed && !READ_ONCE(r->packet.ptl)) {
if (test_and_set_bit(SSH_REQUEST_SF_COMPLETED_BIT, &r->state))
return true;
ssh_rtl_complete_with_status(r, -ECANCELED);
return true;
}
rtl = ssh_request_rtl(r);
spin_lock(&rtl->queue.lock);
/*
* Note: 1) Requests cannot be re-submitted. 2) If a request is
* queued, it cannot be "transmitting"/"pending" yet. Thus, if we
* successfully remove the request here, we have removed all its
* occurrences in the system.
*/
remove = test_and_clear_bit(SSH_REQUEST_SF_QUEUED_BIT, &r->state);
if (!remove) {
spin_unlock(&rtl->queue.lock);
return false;
}
set_bit(SSH_REQUEST_SF_LOCKED_BIT, &r->state);
list_del(&r->node);
spin_unlock(&rtl->queue.lock);
ssh_request_put(r); /* Drop reference obtained from queue. */
if (test_and_set_bit(SSH_REQUEST_SF_COMPLETED_BIT, &r->state))
return true;
ssh_rtl_complete_with_status(r, -ECANCELED);
return true;
}
static bool ssh_rtl_cancel_pending(struct ssh_request *r)
{
/* If the packet is already locked, it's going to be removed shortly. */
if (test_and_set_bit(SSH_REQUEST_SF_LOCKED_BIT, &r->state))
return true;
/*
* Now that we have locked the packet, we have guaranteed that it can't
* be added to the system any more. If ptl is NULL, the locked
* check in ssh_rtl_submit() has not been run and any submission,
* currently in progress or called later, won't add the packet. Thus we
* can directly complete it.
*
* The implicit memory barrier of test_and_set_bit() should be enough
* to ensure that the correct order (first lock, then check ptl) is
* ensured. This is paired with the barrier in ssh_rtl_submit().
*/
if (!READ_ONCE(r->packet.ptl)) {
if (test_and_set_bit(SSH_REQUEST_SF_COMPLETED_BIT, &r->state))
return true;
ssh_rtl_complete_with_status(r, -ECANCELED);
return true;
}
/*
* Try to cancel the packet. If the packet has not been completed yet,
* this will subsequently (and synchronously) call the completion
* callback of the packet, which will complete the request.
*/
ssh_ptl_cancel(&r->packet);
/*
* If the packet has been completed with success, i.e. has not been
* canceled by the above call, the request may not have been completed
* yet (may be waiting for a response). Check if we need to do this
* here.
*/
if (test_and_set_bit(SSH_REQUEST_SF_COMPLETED_BIT, &r->state))
return true;
ssh_rtl_queue_remove(r);
ssh_rtl_pending_remove(r);
ssh_rtl_complete_with_status(r, -ECANCELED);
return true;
}
/**
* ssh_rtl_cancel() - Cancel request.
* @rqst: The request to cancel.
* @pending: Whether to also cancel pending requests.
*
* Cancels the given request. If @pending is %false, this will not cancel
* pending requests, i.e. requests that have already been submitted to the
* packet layer but not been completed yet. If @pending is %true, this will
* cancel the given request regardless of the state it is in.
*
* If the request has been canceled by calling this function, both completion
* and release callbacks of the request will be executed in a reasonable
* time-frame. This may happen during execution of this function, however,
* there is no guarantee for this. For example, a request currently
* transmitting will be canceled/completed only after transmission has
* completed, and the respective callbacks will be executed on the transmitter
* thread, which may happen during, but also some time after execution of the
* cancel function.
*
* Return: Returns %true if the given request has been canceled or completed,
* either by this function or prior to calling this function, %false
* otherwise. If @pending is %true, this function will always return %true.
*/
bool ssh_rtl_cancel(struct ssh_request *rqst, bool pending)
{
struct ssh_rtl *rtl;
bool canceled;
if (test_and_set_bit(SSH_REQUEST_SF_CANCELED_BIT, &rqst->state))
return true;
trace_ssam_request_cancel(rqst);
if (pending)
canceled = ssh_rtl_cancel_pending(rqst);
else
canceled = ssh_rtl_cancel_nonpending(rqst);
/* Note: rtl may be NULL if request has not been submitted yet. */
rtl = ssh_request_rtl(rqst);
if (canceled && rtl)
ssh_rtl_tx_schedule(rtl);
return canceled;
}
static void ssh_rtl_packet_callback(struct ssh_packet *p, int status)
{
struct ssh_request *r = to_ssh_request(p);
if (unlikely(status)) {
set_bit(SSH_REQUEST_SF_LOCKED_BIT, &r->state);
if (test_and_set_bit(SSH_REQUEST_SF_COMPLETED_BIT, &r->state))
return;
/*
* The packet may get canceled even though it has not been
* submitted yet. The request may still be queued. Check the
* queue and remove it if necessary. As the timeout would have
* been started in this function on success, there's no need
* to cancel it here.
*/
ssh_rtl_queue_remove(r);
ssh_rtl_pending_remove(r);
ssh_rtl_complete_with_status(r, status);
ssh_rtl_tx_schedule(ssh_request_rtl(r));
return;
}
/* Update state: Mark as transmitted and clear transmitting. */
set_bit(SSH_REQUEST_SF_TRANSMITTED_BIT, &r->state);
/* Ensure state never gets zero. */
smp_mb__before_atomic();
clear_bit(SSH_REQUEST_SF_TRANSMITTING_BIT, &r->state);
/* If we expect a response, we just need to start the timeout. */
if (test_bit(SSH_REQUEST_TY_HAS_RESPONSE_BIT, &r->state)) {
/*
* Note: This is the only place where the timestamp gets set,
* all other access to it is read-only.
*/
ssh_rtl_timeout_start(r);
return;
}
/*
* If we don't expect a response, lock, remove, and complete the
* request. Note that, at this point, the request is guaranteed to have
* left the queue and no timeout has been started. Thus we only need to
* remove it from pending. If the request has already been completed (it
* may have been canceled) return.
*/
set_bit(SSH_REQUEST_SF_LOCKED_BIT, &r->state);
if (test_and_set_bit(SSH_REQUEST_SF_COMPLETED_BIT, &r->state))
return;
ssh_rtl_pending_remove(r);
ssh_rtl_complete_with_status(r, 0);
ssh_rtl_tx_schedule(ssh_request_rtl(r));
}
static ktime_t ssh_request_get_expiration(struct ssh_request *r, ktime_t timeout)
{
ktime_t timestamp = READ_ONCE(r->timestamp);
if (timestamp != KTIME_MAX)
return ktime_add(timestamp, timeout);
else
return KTIME_MAX;
}
static void ssh_rtl_timeout_reap(struct work_struct *work)
{
struct ssh_rtl *rtl = to_ssh_rtl(work, rtx_timeout.reaper.work);
struct ssh_request *r, *n;
LIST_HEAD(claimed);
ktime_t now = ktime_get_coarse_boottime();
ktime_t timeout = rtl->rtx_timeout.timeout;
ktime_t next = KTIME_MAX;
trace_ssam_rtl_timeout_reap(atomic_read(&rtl->pending.count));
/*
* Mark reaper as "not pending". This is done before checking any
* requests to avoid lost-update type problems.
*/
spin_lock(&rtl->rtx_timeout.lock);
rtl->rtx_timeout.expires = KTIME_MAX;
spin_unlock(&rtl->rtx_timeout.lock);
spin_lock(&rtl->pending.lock);
list_for_each_entry_safe(r, n, &rtl->pending.head, node) {
ktime_t expires = ssh_request_get_expiration(r, timeout);
/*
* Check if the timeout hasn't expired yet. Find out next
* expiration date to be handled after this run.
*/
if (ktime_after(expires, now)) {
next = ktime_before(expires, next) ? expires : next;
continue;
}
/* Avoid further transitions if locked. */
if (test_and_set_bit(SSH_REQUEST_SF_LOCKED_BIT, &r->state))
continue;
/*
* We have now marked the packet as locked. Thus it cannot be
* added to the pending or queued lists again after we've
* removed it here. We can therefore re-use the node of this
* packet temporarily.
*/
clear_bit(SSH_REQUEST_SF_PENDING_BIT, &r->state);
atomic_dec(&rtl->pending.count);
list_move_tail(&r->node, &claimed);
}
spin_unlock(&rtl->pending.lock);
/* Cancel and complete the request. */
list_for_each_entry_safe(r, n, &claimed, node) {
trace_ssam_request_timeout(r);
/*
* At this point we've removed the packet from pending. This
* means that we've obtained the last (only) reference of the
* system to it. Thus we can just complete it.
*/
if (!test_and_set_bit(SSH_REQUEST_SF_COMPLETED_BIT, &r->state))
ssh_rtl_complete_with_status(r, -ETIMEDOUT);
/*
* Drop the reference we've obtained by removing it from the
* pending set.
*/
list_del(&r->node);
ssh_request_put(r);
}
/* Ensure that the reaper doesn't run again immediately. */
next = max(next, ktime_add(now, SSH_RTL_REQUEST_TIMEOUT_RESOLUTION));
if (next != KTIME_MAX)
ssh_rtl_timeout_reaper_mod(rtl, now, next);
ssh_rtl_tx_schedule(rtl);
}
static void ssh_rtl_rx_event(struct ssh_rtl *rtl, const struct ssh_command *cmd,
const struct ssam_span *data)
{
trace_ssam_rx_event_received(cmd, data->len);
rtl_dbg(rtl, "rtl: handling event (rqid: %#06x)\n",
get_unaligned_le16(&cmd->rqid));
rtl->ops.handle_event(rtl, cmd, data);
}
static void ssh_rtl_rx_command(struct ssh_ptl *p, const struct ssam_span *data)
{
struct ssh_rtl *rtl = to_ssh_rtl(p, ptl);
struct device *dev = &p->serdev->dev;
struct ssh_command *command;
struct ssam_span command_data;
if (sshp_parse_command(dev, data, &command, &command_data))
return;
/*
* Check if the message was intended for us. If not, drop it.
*
* Note: We will need to change this to handle debug messages. On newer
* generation devices, these seem to be sent to SSAM_SSH_TID_DEBUG. We
* as host can still receive them as they can be forwarded via an
* override option on SAM, but doing so does not change the target ID
* to SSAM_SSH_TID_HOST.
*/
if (command->tid != SSAM_SSH_TID_HOST) {
rtl_warn(rtl, "rtl: dropping message not intended for us (tid = %#04x)\n",
command->tid);
return;
}
if (ssh_rqid_is_event(get_unaligned_le16(&command->rqid)))
ssh_rtl_rx_event(rtl, command, &command_data);
else
ssh_rtl_complete(rtl, command, &command_data);
}
static void ssh_rtl_rx_data(struct ssh_ptl *p, const struct ssam_span *data)
{
if (!data->len) {
ptl_err(p, "rtl: rx: no data frame payload\n");
return;
}
switch (data->ptr[0]) {
case SSH_PLD_TYPE_CMD:
ssh_rtl_rx_command(p, data);
break;
default:
ptl_err(p, "rtl: rx: unknown frame payload type (type: %#04x)\n",
data->ptr[0]);
break;
}
}
static void ssh_rtl_packet_release(struct ssh_packet *p)
{
struct ssh_request *rqst;
rqst = to_ssh_request(p);
rqst->ops->release(rqst);
}
static const struct ssh_packet_ops ssh_rtl_packet_ops = {
.complete = ssh_rtl_packet_callback,
.release = ssh_rtl_packet_release,
};
/**
* ssh_request_init() - Initialize SSH request.
* @rqst: The request to initialize.
* @flags: Request flags, determining the type of the request.
* @ops: Request operations.
*
* Initializes the given SSH request and underlying packet. Sets the message
* buffer pointer to %NULL and the message buffer length to zero. This buffer
* has to be set separately via ssh_request_set_data() before submission and
* must contain a valid SSH request message.
*
* Return: Returns zero on success or %-EINVAL if the given flags are invalid.
*/
int ssh_request_init(struct ssh_request *rqst, enum ssam_request_flags flags,
const struct ssh_request_ops *ops)
{
unsigned long type = BIT(SSH_PACKET_TY_BLOCKING_BIT);
/* Unsequenced requests cannot have a response. */
if (flags & SSAM_REQUEST_UNSEQUENCED && flags & SSAM_REQUEST_HAS_RESPONSE)
return -EINVAL;
if (!(flags & SSAM_REQUEST_UNSEQUENCED))
type |= BIT(SSH_PACKET_TY_SEQUENCED_BIT);
ssh_packet_init(&rqst->packet, type, SSH_PACKET_PRIORITY(DATA, 0),
&ssh_rtl_packet_ops);
INIT_LIST_HEAD(&rqst->node);
rqst->state = 0;
if (flags & SSAM_REQUEST_HAS_RESPONSE)
rqst->state |= BIT(SSH_REQUEST_TY_HAS_RESPONSE_BIT);
rqst->timestamp = KTIME_MAX;
rqst->ops = ops;
return 0;
}
/**
* ssh_rtl_init() - Initialize request transport layer.
* @rtl: The request transport layer to initialize.
* @serdev: The underlying serial device, i.e. the lower-level transport.
* @ops: Request transport layer operations.
*
* Initializes the given request transport layer and associated packet
* transport layer. Transmitter and receiver threads must be started
* separately via ssh_rtl_start(), after the request-layer has been
* initialized and the lower-level serial device layer has been set up.
*
* Return: Returns zero on success and a nonzero error code on failure.
*/
int ssh_rtl_init(struct ssh_rtl *rtl, struct serdev_device *serdev,
const struct ssh_rtl_ops *ops)
{
struct ssh_ptl_ops ptl_ops;
int status;
ptl_ops.data_received = ssh_rtl_rx_data;
status = ssh_ptl_init(&rtl->ptl, serdev, &ptl_ops);
if (status)
return status;
spin_lock_init(&rtl->queue.lock);
INIT_LIST_HEAD(&rtl->queue.head);
spin_lock_init(&rtl->pending.lock);
INIT_LIST_HEAD(&rtl->pending.head);
atomic_set_release(&rtl->pending.count, 0);
INIT_WORK(&rtl->tx.work, ssh_rtl_tx_work_fn);
spin_lock_init(&rtl->rtx_timeout.lock);
rtl->rtx_timeout.timeout = SSH_RTL_REQUEST_TIMEOUT;
rtl->rtx_timeout.expires = KTIME_MAX;
INIT_DELAYED_WORK(&rtl->rtx_timeout.reaper, ssh_rtl_timeout_reap);
rtl->ops = *ops;
return 0;
}
/**
* ssh_rtl_destroy() - Deinitialize request transport layer.
* @rtl: The request transport layer to deinitialize.
*
* Deinitializes the given request transport layer and frees resources
* associated with it. If receiver and/or transmitter threads have been
* started, the layer must first be shut down via ssh_rtl_shutdown() before
* this function can be called.
*/
void ssh_rtl_destroy(struct ssh_rtl *rtl)
{
ssh_ptl_destroy(&rtl->ptl);
}
/**
* ssh_rtl_start() - Start request transmitter and receiver.
* @rtl: The request transport layer.
*
* Return: Returns zero on success, a negative error code on failure.
*/
int ssh_rtl_start(struct ssh_rtl *rtl)
{
int status;
status = ssh_ptl_tx_start(&rtl->ptl);
if (status)
return status;
ssh_rtl_tx_schedule(rtl);
status = ssh_ptl_rx_start(&rtl->ptl);
if (status) {
ssh_rtl_flush(rtl, msecs_to_jiffies(5000));
ssh_ptl_tx_stop(&rtl->ptl);
return status;
}
return 0;
}
struct ssh_flush_request {
struct ssh_request base;
struct completion completion;
int status;
};
static void ssh_rtl_flush_request_complete(struct ssh_request *r,
const struct ssh_command *cmd,
const struct ssam_span *data,
int status)
{
struct ssh_flush_request *rqst;
rqst = container_of(r, struct ssh_flush_request, base);
rqst->status = status;
}
static void ssh_rtl_flush_request_release(struct ssh_request *r)
{
struct ssh_flush_request *rqst;
rqst = container_of(r, struct ssh_flush_request, base);
complete_all(&rqst->completion);
}
static const struct ssh_request_ops ssh_rtl_flush_request_ops = {
.complete = ssh_rtl_flush_request_complete,
.release = ssh_rtl_flush_request_release,
};
/**
* ssh_rtl_flush() - Flush the request transport layer.
* @rtl: request transport layer
* @timeout: timeout for the flush operation in jiffies
*
* Queue a special flush request and wait for its completion. This request
* will be completed after all other currently queued and pending requests
* have been completed. Instead of a normal data packet, this request submits
* a special flush packet, meaning that upon completion, also the underlying
* packet transport layer has been flushed.
*
* Flushing the request layer guarantees that all previously submitted
* requests have been fully completed before this call returns. Additionally,
* flushing blocks execution of all later submitted requests until the flush
* has been completed.
*
* If the caller ensures that no new requests are submitted after a call to
* this function, the request transport layer is guaranteed to have no
* remaining requests when this call returns. The same guarantee does not hold
* for the packet layer, on which control packets may still be queued after
* this call.
*
* Return: Returns zero on success, %-ETIMEDOUT if the flush timed out and has
* been canceled as a result of the timeout, or %-ESHUTDOWN if the packet
* and/or request transport layer has been shut down before this call. May
* also return %-EINTR if the underlying packet transmission has been
* interrupted.
*/
int ssh_rtl_flush(struct ssh_rtl *rtl, unsigned long timeout)
{
const unsigned int init_flags = SSAM_REQUEST_UNSEQUENCED;
struct ssh_flush_request rqst;
int status;
ssh_request_init(&rqst.base, init_flags, &ssh_rtl_flush_request_ops);
rqst.base.packet.state |= BIT(SSH_PACKET_TY_FLUSH_BIT);
rqst.base.packet.priority = SSH_PACKET_PRIORITY(FLUSH, 0);
rqst.base.state |= BIT(SSH_REQUEST_TY_FLUSH_BIT);
init_completion(&rqst.completion);
status = ssh_rtl_submit(rtl, &rqst.base);
if (status)
return status;
ssh_request_put(&rqst.base);
if (!wait_for_completion_timeout(&rqst.completion, timeout)) {
ssh_rtl_cancel(&rqst.base, true);
wait_for_completion(&rqst.completion);
}
WARN_ON(rqst.status != 0 && rqst.status != -ECANCELED &&
rqst.status != -ESHUTDOWN && rqst.status != -EINTR);
return rqst.status == -ECANCELED ? -ETIMEDOUT : rqst.status;
}
/**
* ssh_rtl_shutdown() - Shut down request transport layer.
* @rtl: The request transport layer.
*
* Shuts down the request transport layer, removing and canceling all queued
* and pending requests. Requests canceled by this operation will be completed
* with %-ESHUTDOWN as status. Receiver and transmitter threads will be
* stopped, the lower-level packet layer will be shutdown.
*
* As a result of this function, the transport layer will be marked as shut
* down. Submission of requests after the transport layer has been shut down
* will fail with %-ESHUTDOWN.
*/
void ssh_rtl_shutdown(struct ssh_rtl *rtl)
{
struct ssh_request *r, *n;
LIST_HEAD(claimed);
int pending;
set_bit(SSH_RTL_SF_SHUTDOWN_BIT, &rtl->state);
/*
* Ensure that the layer gets marked as shut-down before actually
* stopping it. In combination with the check in ssh_rtl_submit(),
* this guarantees that no new requests can be added and all already
* queued requests are properly canceled.
*/
smp_mb__after_atomic();
/* Remove requests from queue. */
spin_lock(&rtl->queue.lock);
list_for_each_entry_safe(r, n, &rtl->queue.head, node) {
set_bit(SSH_REQUEST_SF_LOCKED_BIT, &r->state);
/* Ensure state never gets zero. */
smp_mb__before_atomic();
clear_bit(SSH_REQUEST_SF_QUEUED_BIT, &r->state);
list_move_tail(&r->node, &claimed);
}
spin_unlock(&rtl->queue.lock);
/*
* We have now guaranteed that the queue is empty and no more new
* requests can be submitted (i.e. it will stay empty). This means that
* calling ssh_rtl_tx_schedule() will not schedule tx.work any more. So
* we can simply call cancel_work_sync() on tx.work here and when that
* returns, we've locked it down. This also means that after this call,
* we don't submit any more packets to the underlying packet layer, so
* we can also shut that down.
*/
cancel_work_sync(&rtl->tx.work);
ssh_ptl_shutdown(&rtl->ptl);
cancel_delayed_work_sync(&rtl->rtx_timeout.reaper);
/*
* Shutting down the packet layer should also have canceled all
* requests. Thus the pending set should be empty. Attempt to handle
* this gracefully anyways, even though this should be dead code.
*/
pending = atomic_read(&rtl->pending.count);
if (WARN_ON(pending)) {
spin_lock(&rtl->pending.lock);
list_for_each_entry_safe(r, n, &rtl->pending.head, node) {
set_bit(SSH_REQUEST_SF_LOCKED_BIT, &r->state);
/* Ensure state never gets zero. */
smp_mb__before_atomic();
clear_bit(SSH_REQUEST_SF_PENDING_BIT, &r->state);
list_move_tail(&r->node, &claimed);
}
spin_unlock(&rtl->pending.lock);
}
/* Finally, cancel and complete the requests we claimed before. */
list_for_each_entry_safe(r, n, &claimed, node) {
/*
* We need test_and_set() because we still might compete with
* cancellation.
*/
if (!test_and_set_bit(SSH_REQUEST_SF_COMPLETED_BIT, &r->state))
ssh_rtl_complete_with_status(r, -ESHUTDOWN);
/*
* Drop the reference we've obtained by removing it from the
* lists.
*/
list_del(&r->node);
ssh_request_put(r);
}
}
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