// SPDX-License-Identifier: GPL-2.0+
/*
* 8250_dma.c - DMA Engine API support for 8250.c
*
* Copyright (C) 2013 Intel Corporation
*/
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/serial_reg.h>
#include <linux/dma-mapping.h>
#include "8250.h"
static void __dma_tx_complete(void *param)
{
struct uart_8250_port *p = param;
struct uart_8250_dma *dma = p->dma;
struct tty_port *tport = &p->port.state->port;
unsigned long flags;
int ret;
dma_sync_single_for_cpu(dma->txchan->device->dev, dma->tx_addr,
UART_XMIT_SIZE, DMA_TO_DEVICE);
uart_port_lock_irqsave(&p->port, &flags);
dma->tx_running = 0;
uart_xmit_advance(&p->port, dma->tx_size);
if (kfifo_len(&tport->xmit_fifo) < WAKEUP_CHARS)
uart_write_wakeup(&p->port);
ret = serial8250_tx_dma(p);
if (ret || !dma->tx_running)
serial8250_set_THRI(p);
uart_port_unlock_irqrestore(&p->port, flags);
}
static void __dma_rx_complete(struct uart_8250_port *p)
{
struct uart_8250_dma *dma = p->dma;
struct tty_port *tty_port = &p->port.state->port;
struct dma_tx_state state;
enum dma_status dma_status;
int count;
/*
* New DMA Rx can be started during the completion handler before it
* could acquire port's lock and it might still be ongoing. Don't to
* anything in such case.
*/
dma_status = dmaengine_tx_status(dma->rxchan, dma->rx_cookie, &state);
if (dma_status == DMA_IN_PROGRESS)
return;
count = dma->rx_size - state.residue;
tty_insert_flip_string(tty_port, dma->rx_buf, count);
p->port.icount.rx += count;
dma->rx_running = 0;
tty_flip_buffer_push(tty_port);
}
static void dma_rx_complete(void *param)
{
struct uart_8250_port *p = param;
struct uart_8250_dma *dma = p->dma;
unsigned long flags;
uart_port_lock_irqsave(&p->port, &flags);
if (dma->rx_running)
__dma_rx_complete(p);
/*
* Cannot be combined with the previous check because __dma_rx_complete()
* changes dma->rx_running.
*/
if (!dma->rx_running && (serial_lsr_in(p) & UART_LSR_DR))
p->dma->rx_dma(p);
uart_port_unlock_irqrestore(&p->port, flags);
}
int serial8250_tx_dma(struct uart_8250_port *p)
{
struct uart_8250_dma *dma = p->dma;
struct tty_port *tport = &p->port.state->port;
struct dma_async_tx_descriptor *desc;
struct uart_port *up = &p->port;
struct scatterlist *sg;
struct scatterlist sgl[2];
int i;
int ret;
if (dma->tx_running) {
if (up->x_char) {
dmaengine_pause(dma->txchan);
uart_xchar_out(up, UART_TX);
dmaengine_resume(dma->txchan);
}
return 0;
} else if (up->x_char) {
uart_xchar_out(up, UART_TX);
}
if (uart_tx_stopped(&p->port) || kfifo_is_empty(&tport->xmit_fifo)) {
/* We have been called from __dma_tx_complete() */
return 0;
}
serial8250_do_prepare_tx_dma(p);
sg_init_table(sgl, ARRAY_SIZE(sgl));
ret = kfifo_dma_out_prepare_mapped(&tport->xmit_fifo, sgl, ARRAY_SIZE(sgl),
UART_XMIT_SIZE, dma->tx_addr);
dma->tx_size = 0;
for_each_sg(sgl, sg, ret, i)
dma->tx_size += sg_dma_len(sg);
desc = dmaengine_prep_slave_sg(dma->txchan, sgl, ret,
DMA_MEM_TO_DEV,
DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
if (!desc) {
ret = -EBUSY;
goto err;
}
dma->tx_running = 1;
desc->callback = __dma_tx_complete;
desc->callback_param = p;
dma->tx_cookie = dmaengine_submit(desc);
dma_sync_single_for_device(dma->txchan->device->dev, dma->tx_addr,
UART_XMIT_SIZE, DMA_TO_DEVICE);
dma_async_issue_pending(dma->txchan);
serial8250_clear_THRI(p);
dma->tx_err = 0;
return 0;
err:
dma->tx_err = 1;
return ret;
}
int serial8250_rx_dma(struct uart_8250_port *p)
{
struct uart_8250_dma *dma = p->dma;
struct dma_async_tx_descriptor *desc;
if (dma->rx_running)
return 0;
serial8250_do_prepare_rx_dma(p);
desc = dmaengine_prep_slave_single(dma->rxchan, dma->rx_addr,
dma->rx_size, DMA_DEV_TO_MEM,
DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
if (!desc)
return -EBUSY;
dma->rx_running = 1;
desc->callback = dma_rx_complete;
desc->callback_param = p;
dma->rx_cookie = dmaengine_submit(desc);
dma_async_issue_pending(dma->rxchan);
return 0;
}
void serial8250_rx_dma_flush(struct uart_8250_port *p)
{
struct uart_8250_dma *dma = p->dma;
if (dma->rx_running) {
dmaengine_pause(dma->rxchan);
__dma_rx_complete(p);
dmaengine_terminate_async(dma->rxchan);
}
}
EXPORT_SYMBOL_GPL(serial8250_rx_dma_flush);
int serial8250_request_dma(struct uart_8250_port *p)
{
struct uart_8250_dma *dma = p->dma;
phys_addr_t rx_dma_addr = dma->rx_dma_addr ?
dma->rx_dma_addr : p->port.mapbase;
phys_addr_t tx_dma_addr = dma->tx_dma_addr ?
dma->tx_dma_addr : p->port.mapbase;
dma_cap_mask_t mask;
struct dma_slave_caps caps;
int ret;
/* Default slave configuration parameters */
dma->rxconf.direction = DMA_DEV_TO_MEM;
dma->rxconf.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
dma->rxconf.src_addr = rx_dma_addr + UART_RX;
dma->txconf.direction = DMA_MEM_TO_DEV;
dma->txconf.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
dma->txconf.dst_addr = tx_dma_addr + UART_TX;
dma_cap_zero(mask);
dma_cap_set(DMA_SLAVE, mask);
/* Get a channel for RX */
dma->rxchan = dma_request_slave_channel_compat(mask,
dma->fn, dma->rx_param,
p->port.dev, "rx");
if (!dma->rxchan)
return -ENODEV;
/* 8250 rx dma requires dmaengine driver to support pause/terminate */
ret = dma_get_slave_caps(dma->rxchan, &caps);
if (ret)
goto release_rx;
if (!caps.cmd_pause || !caps.cmd_terminate ||
caps.residue_granularity == DMA_RESIDUE_GRANULARITY_DESCRIPTOR) {
ret = -EINVAL;
goto release_rx;
}
dmaengine_slave_config(dma->rxchan, &dma->rxconf);
/* Get a channel for TX */
dma->txchan = dma_request_slave_channel_compat(mask,
dma->fn, dma->tx_param,
p->port.dev, "tx");
if (!dma->txchan) {
ret = -ENODEV;
goto release_rx;
}
/* 8250 tx dma requires dmaengine driver to support terminate */
ret = dma_get_slave_caps(dma->txchan, &caps);
if (ret)
goto err;
if (!caps.cmd_terminate) {
ret = -EINVAL;
goto err;
}
dmaengine_slave_config(dma->txchan, &dma->txconf);
/* RX buffer */
if (!dma->rx_size)
dma->rx_size = PAGE_SIZE;
dma->rx_buf = dma_alloc_coherent(dma->rxchan->device->dev, dma->rx_size,
&dma->rx_addr, GFP_KERNEL);
if (!dma->rx_buf) {
ret = -ENOMEM;
goto err;
}
/* TX buffer */
dma->tx_addr = dma_map_single(dma->txchan->device->dev,
p->port.state->port.xmit_buf,
UART_XMIT_SIZE,
DMA_TO_DEVICE);
if (dma_mapping_error(dma->txchan->device->dev, dma->tx_addr)) {
dma_free_coherent(dma->rxchan->device->dev, dma->rx_size,
dma->rx_buf, dma->rx_addr);
ret = -ENOMEM;
goto err;
}
dev_dbg_ratelimited(p->port.dev, "got both dma channels\n");
return 0;
err:
dma_release_channel(dma->txchan);
release_rx:
dma_release_channel(dma->rxchan);
return ret;
}
EXPORT_SYMBOL_GPL(serial8250_request_dma);
void serial8250_release_dma(struct uart_8250_port *p)
{
struct uart_8250_dma *dma = p->dma;
if (!dma)
return;
/* Release RX resources */
dmaengine_terminate_sync(dma->rxchan);
dma_free_coherent(dma->rxchan->device->dev, dma->rx_size, dma->rx_buf,
dma->rx_addr);
dma_release_channel(dma->rxchan);
dma->rxchan = NULL;
/* Release TX resources */
dmaengine_terminate_sync(dma->txchan);
dma_unmap_single(dma->txchan->device->dev, dma->tx_addr,
UART_XMIT_SIZE, DMA_TO_DEVICE);
dma_release_channel(dma->txchan);
dma->txchan = NULL;
dma->tx_running = 0;
dev_dbg_ratelimited(p->port.dev, "dma channels released\n");
}
EXPORT_SYMBOL_GPL(serial8250_release_dma);
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