// SPDX-License-Identifier: GPL-2.0-or-later /* * Copyright (C) 2014 Linaro Ltd. * Author: Ashwin Chaugule <[email protected]> * * PCC (Platform Communication Channel) is defined in the ACPI 5.0+ * specification. It is a mailbox like mechanism to allow clients * such as CPPC (Collaborative Processor Performance Control), RAS * (Reliability, Availability and Serviceability) and MPST (Memory * Node Power State Table) to talk to the platform (e.g. BMC) through * shared memory regions as defined in the PCC table entries. The PCC * specification supports a Doorbell mechanism for the PCC clients * to notify the platform about new data. This Doorbell information * is also specified in each PCC table entry. * * Typical high level flow of operation is: * * PCC Reads: * * Client tries to acquire a channel lock. * * After it is acquired it writes READ cmd in communication region cmd * address. * * Client issues mbox_send_message() which rings the PCC doorbell * for its PCC channel. * * If command completes, then client has control over channel and * it can proceed with its reads. * * Client releases lock. * * PCC Writes: * * Client tries to acquire channel lock. * * Client writes to its communication region after it acquires a * channel lock. * * Client writes WRITE cmd in communication region cmd address. * * Client issues mbox_send_message() which rings the PCC doorbell * for its PCC channel. * * If command completes, then writes have succeeded and it can release * the channel lock. * * There is a Nominal latency defined for each channel which indicates * how long to wait until a command completes. If command is not complete * the client needs to retry or assume failure. * * For more details about PCC, please see the ACPI specification from * http://www.uefi.org/ACPIv5.1 Section 14. * * This file implements PCC as a Mailbox controller and allows for PCC * clients to be implemented as its Mailbox Client Channels. */ #include <linux/acpi.h> #include <linux/delay.h> #include <linux/io.h> #include <linux/init.h> #include <linux/interrupt.h> #include <linux/list.h> #include <linux/log2.h> #include <linux/platform_device.h> #include <linux/mailbox_controller.h> #include <linux/mailbox_client.h> #include <linux/io-64-nonatomic-lo-hi.h> #include <acpi/pcc.h> #include "mailbox.h" #define MBOX_IRQ_NAME … /** * struct pcc_chan_reg - PCC register bundle * * @vaddr: cached virtual address for this register * @gas: pointer to the generic address structure for this register * @preserve_mask: bitmask to preserve when writing to this register * @set_mask: bitmask to set when writing to this register * @status_mask: bitmask to determine and/or update the status for this register */ struct pcc_chan_reg { … }; /** * struct pcc_chan_info - PCC channel specific information * * @chan: PCC channel information with Shared Memory Region info * @db: PCC register bundle for the doorbell register * @plat_irq_ack: PCC register bundle for the platform interrupt acknowledge * register * @cmd_complete: PCC register bundle for the command complete check register * @cmd_update: PCC register bundle for the command complete update register * @error: PCC register bundle for the error status register * @plat_irq: platform interrupt * @type: PCC subspace type * @plat_irq_flags: platform interrupt flags * @chan_in_use: this flag is used just to check if the interrupt needs * handling when it is shared. Since only one transfer can occur * at a time and mailbox takes care of locking, this flag can be * accessed without a lock. Note: the type only support the * communication from OSPM to Platform, like type3, use it, and * other types completely ignore it. */ struct pcc_chan_info { … }; #define to_pcc_chan_info(c) … static struct pcc_chan_info *chan_info; static int pcc_chan_count; static int pcc_send_data(struct mbox_chan *chan, void *data); /* * PCC can be used with perf critical drivers such as CPPC * So it makes sense to locally cache the virtual address and * use it to read/write to PCC registers such as doorbell register * * The below read_register and write_registers are used to read and * write from perf critical registers such as PCC doorbell register */ static void read_register(void __iomem *vaddr, u64 *val, unsigned int bit_width) { … } static void write_register(void __iomem *vaddr, u64 val, unsigned int bit_width) { … } static int pcc_chan_reg_read(struct pcc_chan_reg *reg, u64 *val) { … } static int pcc_chan_reg_write(struct pcc_chan_reg *reg, u64 val) { … } static int pcc_chan_reg_read_modify_write(struct pcc_chan_reg *reg) { … } /** * pcc_map_interrupt - Map a PCC subspace GSI to a linux IRQ number * @interrupt: GSI number. * @flags: interrupt flags * * Returns: a valid linux IRQ number on success * 0 or -EINVAL on failure */ static int pcc_map_interrupt(u32 interrupt, u32 flags) { … } static bool pcc_chan_plat_irq_can_be_shared(struct pcc_chan_info *pchan) { … } static bool pcc_mbox_cmd_complete_check(struct pcc_chan_info *pchan) { … } /** * pcc_mbox_irq - PCC mailbox interrupt handler * @irq: interrupt number * @p: data/cookie passed from the caller to identify the channel * * Returns: IRQ_HANDLED if interrupt is handled or IRQ_NONE if not */ static irqreturn_t pcc_mbox_irq(int irq, void *p) { … } /** * pcc_mbox_request_channel - PCC clients call this function to * request a pointer to their PCC subspace, from which they * can get the details of communicating with the remote. * @cl: Pointer to Mailbox client, so we know where to bind the * Channel. * @subspace_id: The PCC Subspace index as parsed in the PCC client * ACPI package. This is used to lookup the array of PCC * subspaces as parsed by the PCC Mailbox controller. * * Return: Pointer to the PCC Mailbox Channel if successful or ERR_PTR. */ struct pcc_mbox_chan * pcc_mbox_request_channel(struct mbox_client *cl, int subspace_id) { … } EXPORT_SYMBOL_GPL(…); /** * pcc_mbox_free_channel - Clients call this to free their Channel. * * @pchan: Pointer to the PCC mailbox channel as returned by * pcc_mbox_request_channel() */ void pcc_mbox_free_channel(struct pcc_mbox_chan *pchan) { … } EXPORT_SYMBOL_GPL(…); /** * pcc_send_data - Called from Mailbox Controller code. Used * here only to ring the channel doorbell. The PCC client * specific read/write is done in the client driver in * order to maintain atomicity over PCC channel once * OS has control over it. See above for flow of operations. * @chan: Pointer to Mailbox channel over which to send data. * @data: Client specific data written over channel. Used here * only for debug after PCC transaction completes. * * Return: Err if something failed else 0 for success. */ static int pcc_send_data(struct mbox_chan *chan, void *data) { … } /** * pcc_startup - Called from Mailbox Controller code. Used here * to request the interrupt. * @chan: Pointer to Mailbox channel to startup. * * Return: Err if something failed else 0 for success. */ static int pcc_startup(struct mbox_chan *chan) { … } /** * pcc_shutdown - Called from Mailbox Controller code. Used here * to free the interrupt. * @chan: Pointer to Mailbox channel to shutdown. */ static void pcc_shutdown(struct mbox_chan *chan) { … } static const struct mbox_chan_ops pcc_chan_ops = …; /** * parse_pcc_subspace - Count PCC subspaces defined * @header: Pointer to the ACPI subtable header under the PCCT. * @end: End of subtable entry. * * Return: If we find a PCC subspace entry of a valid type, return 0. * Otherwise, return -EINVAL. * * This gets called for each entry in the PCC table. */ static int parse_pcc_subspace(union acpi_subtable_headers *header, const unsigned long end) { … } static int pcc_chan_reg_init(struct pcc_chan_reg *reg, struct acpi_generic_address *gas, u64 preserve_mask, u64 set_mask, u64 status_mask, char *name) { … } /** * pcc_parse_subspace_irq - Parse the PCC IRQ and PCC ACK register * * @pchan: Pointer to the PCC channel info structure. * @pcct_entry: Pointer to the ACPI subtable header. * * Return: 0 for Success, else errno. * * There should be one entry per PCC channel. This gets called for each * entry in the PCC table. This uses PCCY Type1 structure for all applicable * types(Type 1-4) to fetch irq */ static int pcc_parse_subspace_irq(struct pcc_chan_info *pchan, struct acpi_subtable_header *pcct_entry) { … } /** * pcc_parse_subspace_db_reg - Parse the PCC doorbell register * * @pchan: Pointer to the PCC channel info structure. * @pcct_entry: Pointer to the ACPI subtable header. * * Return: 0 for Success, else errno. */ static int pcc_parse_subspace_db_reg(struct pcc_chan_info *pchan, struct acpi_subtable_header *pcct_entry) { … } /** * pcc_parse_subspace_shmem - Parse the PCC Shared Memory Region information * * @pchan: Pointer to the PCC channel info structure. * @pcct_entry: Pointer to the ACPI subtable header. * */ static void pcc_parse_subspace_shmem(struct pcc_chan_info *pchan, struct acpi_subtable_header *pcct_entry) { … } /** * acpi_pcc_probe - Parse the ACPI tree for the PCCT. * * Return: 0 for Success, else errno. */ static int __init acpi_pcc_probe(void) { … } /** * pcc_mbox_probe - Called when we find a match for the * PCCT platform device. This is purely used to represent * the PCCT as a virtual device for registering with the * generic Mailbox framework. * * @pdev: Pointer to platform device returned when a match * is found. * * Return: 0 for Success, else errno. */ static int pcc_mbox_probe(struct platform_device *pdev) { … } static struct platform_driver pcc_mbox_driver = …; static int __init pcc_init(void) { … } /* * Make PCC init postcore so that users of this mailbox * such as the ACPI Processor driver have it available * at their init. */ postcore_initcall(pcc_init);
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