Message-ID: <20241014164955.00003439@Huawei.com>
Date: Mon, 14 Oct 2024 16:49:55 +0100
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: <shiju.jose@...wei.com>
CC: <linux-edac@...r.kernel.org>, <linux-cxl@...r.kernel.org>,
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Subject: Re: [PATCH v13 13/18] ACPI:RAS2: Add ACPI RAS2 driver

On Wed, 9 Oct 2024 13:41:14 +0100
<shiju.jose@...wei.com> wrote:

> From: Shiju Jose <shiju.jose@...wei.com>
> 
> Add support for ACPI RAS2 feature table (RAS2) defined in the
> ACPI 6.5 Specification, section 5.2.21.
> Driver contains RAS2 Init, which extracts the RAS2 table and driver
> adds platform device for each memory feature which binds to the
> RAS2 memory driver.
> 
> Driver uses PCC mailbox to communicate with the ACPI HW and the
> driver adds OSPM interfaces to send RAS2 commands.
> 
> Co-developed-by: A Somasundaram <somasundaram.a@....com>
> Signed-off-by: A Somasundaram <somasundaram.a@....com>
> Co-developed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> Signed-off-by: Shiju Jose <shiju.jose@...wei.com>
Rafael, could you take a look at this from ACPI side of things?

I'm fine with this, though maybe a co-developed on this particular
patch over emphasizes my involvement!

No comments inline, just left the context for Rafael if he doesn't
have the original patch to hand.

> ---
>  drivers/acpi/Kconfig     |  10 +
>  drivers/acpi/Makefile    |   1 +
>  drivers/acpi/ras2.c      | 391 +++++++++++++++++++++++++++++++++++++++
>  include/acpi/ras2_acpi.h |  60 ++++++
>  4 files changed, 462 insertions(+)
>  create mode 100755 drivers/acpi/ras2.c
>  create mode 100644 include/acpi/ras2_acpi.h
> 
> diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
> index e3a7c2aedd5f..482080f1f0c5 100644
> --- a/drivers/acpi/Kconfig
> +++ b/drivers/acpi/Kconfig
> @@ -284,6 +284,16 @@ config ACPI_CPPC_LIB
>  	  If your platform does not support CPPC in firmware,
>  	  leave this option disabled.
>  
> +config ACPI_RAS2
> +	bool "ACPI RAS2 driver"
> +	select MAILBOX
> +	select PCC
> +	help
> +	  The driver adds support for ACPI RAS2 feature table(extracts RAS2
> +	  table from OS system table) and OSPM interfaces to send RAS2
> +	  commands via PCC mailbox subspace. Driver adds platform device for
> +	  the RAS2 memory features which binds to the RAS2 memory driver.
> +
>  config ACPI_PROCESSOR
>  	tristate "Processor"
>  	depends on X86 || ARM64 || LOONGARCH || RISCV
> diff --git a/drivers/acpi/Makefile b/drivers/acpi/Makefile
> index 61ca4afe83dc..84e2a2519bae 100644
> --- a/drivers/acpi/Makefile
> +++ b/drivers/acpi/Makefile
> @@ -100,6 +100,7 @@ obj-$(CONFIG_ACPI_EC_DEBUGFS)	+= ec_sys.o
>  obj-$(CONFIG_ACPI_BGRT)		+= bgrt.o
>  obj-$(CONFIG_ACPI_CPPC_LIB)	+= cppc_acpi.o
>  obj-$(CONFIG_ACPI_SPCR_TABLE)	+= spcr.o
> +obj-$(CONFIG_ACPI_RAS2)		+= ras2.o
>  obj-$(CONFIG_ACPI_DEBUGGER_USER) += acpi_dbg.o
>  obj-$(CONFIG_ACPI_PPTT) 	+= pptt.o
>  obj-$(CONFIG_ACPI_PFRUT)	+= pfr_update.o pfr_telemetry.o
> diff --git a/drivers/acpi/ras2.c b/drivers/acpi/ras2.c
> new file mode 100755
> index 000000000000..5daf1510d19e
> --- /dev/null
> +++ b/drivers/acpi/ras2.c
> @@ -0,0 +1,391 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Implementation of ACPI RAS2 driver.
> + *
> + * Copyright (c) 2024 HiSilicon Limited.
> + *
> + * Support for RAS2 - ACPI 6.5 Specification, section 5.2.21
> + *
> + * Driver contains ACPI RAS2 init, which extracts the ACPI RAS2 table and
> + * get the PCC channel subspace for communicating with the ACPI compliant
> + * HW platform which supports ACPI RAS2. Driver adds platform devices
> + * for each RAS2 memory feature which binds to the memory ACPI RAS2 driver.
> + */
> +
> +#define pr_fmt(fmt)    "ACPI RAS2: " fmt
> +
> +#include <linux/delay.h>
> +#include <linux/export.h>
> +#include <linux/ktime.h>
> +#include <linux/platform_device.h>
> +#include <acpi/pcc.h>
> +#include <acpi/ras2_acpi.h>
> +
> +/*
> + * Arbitrary Retries for PCC commands because the
> + * remote processor could be much slower to reply.
> + */
> +#define RAS2_NUM_RETRIES 600
> +
> +#define RAS2_FEATURE_TYPE_MEMORY        0x00
> +
> +/* global variables for the RAS2 PCC subspaces */
> +static DEFINE_MUTEX(ras2_pcc_subspace_lock);
> +static LIST_HEAD(ras2_pcc_subspaces);
> +
> +static int ras2_report_cap_error(u32 cap_status)
> +{
> +	switch (cap_status) {
> +	case ACPI_RAS2_NOT_VALID:
> +	case ACPI_RAS2_NOT_SUPPORTED:
> +		return -EPERM;
> +	case ACPI_RAS2_BUSY:
> +		return -EBUSY;
> +	case ACPI_RAS2_FAILED:
> +	case ACPI_RAS2_ABORTED:
> +	case ACPI_RAS2_INVALID_DATA:
> +		return -EINVAL;
> +	default: /* 0 or other, Success */
> +		return 0;
> +	}
> +}
> +
> +static int ras2_check_pcc_chan(struct ras2_pcc_subspace *pcc_subspace)
> +{
> +	struct acpi_ras2_shared_memory __iomem *generic_comm_base = pcc_subspace->pcc_comm_addr;
> +	ktime_t next_deadline = ktime_add(ktime_get(), pcc_subspace->deadline);
> +	u32 cap_status;
> +	u16 status;
> +	u32 ret;
> +
> +	while (!ktime_after(ktime_get(), next_deadline)) {
> +		/*
> +		 * As per ACPI spec, the PCC space will be initialized by
> +		 * platform and should have set the command completion bit when
> +		 * PCC can be used by OSPM
> +		 */
> +		status = readw_relaxed(&generic_comm_base->status);
> +		if (status & RAS2_PCC_CMD_ERROR) {
> +			cap_status = readw_relaxed(&generic_comm_base->set_capabilities_status);
> +			ret = ras2_report_cap_error(cap_status);
> +
> +			status &= ~RAS2_PCC_CMD_ERROR;
> +			writew_relaxed(status, &generic_comm_base->status);
> +			return ret;
> +		}
> +		if (status & RAS2_PCC_CMD_COMPLETE)
> +			return 0;
> +		/*
> +		 * Reducing the bus traffic in case this loop takes longer than
> +		 * a few retries.
> +		 */
> +		msleep(10);
> +	}
> +
> +	return -EIO;
> +}
> +
> +/**
> + * ras2_send_pcc_cmd() - Send RAS2 command via PCC channel
> + * @ras2_ctx:	pointer to the RAS2 context structure
> + * @cmd:	command to send
> + *
> + * Returns: 0 on success, an error otherwise
> + */
> +int ras2_send_pcc_cmd(struct ras2_scrub_ctx *ras2_ctx, u16 cmd)
> +{
> +	struct ras2_pcc_subspace *pcc_subspace = ras2_ctx->pcc_subspace;
> +	struct acpi_ras2_shared_memory *generic_comm_base = pcc_subspace->pcc_comm_addr;
> +	static ktime_t last_cmd_cmpl_time, last_mpar_reset;
> +	struct mbox_chan *pcc_channel;
> +	unsigned int time_delta;
> +	static int mpar_count;
> +	int ret;
> +
> +	guard(mutex)(&ras2_pcc_subspace_lock);
> +	ret = ras2_check_pcc_chan(pcc_subspace);
> +	if (ret < 0)
> +		return ret;
> +	pcc_channel = pcc_subspace->pcc_chan->mchan;
> +
> +	/*
> +	 * Handle the Minimum Request Turnaround Time(MRTT)
> +	 * "The minimum amount of time that OSPM must wait after the completion
> +	 * of a command before issuing the next command, in microseconds"
> +	 */
> +	if (pcc_subspace->pcc_mrtt) {
> +		time_delta = ktime_us_delta(ktime_get(), last_cmd_cmpl_time);
> +		if (pcc_subspace->pcc_mrtt > time_delta)
> +			udelay(pcc_subspace->pcc_mrtt - time_delta);
> +	}
> +
> +	/*
> +	 * Handle the non-zero Maximum Periodic Access Rate(MPAR)
> +	 * "The maximum number of periodic requests that the subspace channel can
> +	 * support, reported in commands per minute. 0 indicates no limitation."
> +	 *
> +	 * This parameter should be ideally zero or large enough so that it can
> +	 * handle maximum number of requests that all the cores in the system can
> +	 * collectively generate. If it is not, we will follow the spec and just
> +	 * not send the request to the platform after hitting the MPAR limit in
> +	 * any 60s window
> +	 */
> +	if (pcc_subspace->pcc_mpar) {
> +		if (mpar_count == 0) {
> +			time_delta = ktime_ms_delta(ktime_get(), last_mpar_reset);
> +			if (time_delta < 60 * MSEC_PER_SEC) {
> +				dev_dbg(ras2_ctx->dev,
> +					"PCC cmd not sent due to MPAR limit");
> +				return -EIO;
> +			}
> +			last_mpar_reset = ktime_get();
> +			mpar_count = pcc_subspace->pcc_mpar;
> +		}
> +		mpar_count--;
> +	}
> +
> +	/* Write to the shared comm region. */
> +	writew_relaxed(cmd, &generic_comm_base->command);
> +
> +	/* Flip CMD COMPLETE bit */
> +	writew_relaxed(0, &generic_comm_base->status);
> +
> +	/* Ring doorbell */
> +	ret = mbox_send_message(pcc_channel, &cmd);
> +	if (ret < 0) {
> +		dev_err(ras2_ctx->dev,
> +			"Err sending PCC mbox message. cmd:%d, ret:%d\n",
> +			cmd, ret);
> +		return ret;
> +	}
> +
> +	/*
> +	 * If Minimum Request Turnaround Time is non-zero, we need
> +	 * to record the completion time of both READ and WRITE
> +	 * command for proper handling of MRTT, so we need to check
> +	 * for pcc_mrtt in addition to CMD_READ
> +	 */
> +	if (cmd == RAS2_PCC_CMD_EXEC || pcc_subspace->pcc_mrtt) {
> +		ret = ras2_check_pcc_chan(pcc_subspace);
> +		if (pcc_subspace->pcc_mrtt)
> +			last_cmd_cmpl_time = ktime_get();
> +	}
> +
> +	if (pcc_channel->mbox->txdone_irq)
> +		mbox_chan_txdone(pcc_channel, ret);
> +	else
> +		mbox_client_txdone(pcc_channel, ret);
> +
> +	return ret >= 0 ? 0 : ret;
> +}
> +EXPORT_SYMBOL_GPL(ras2_send_pcc_cmd);
> +
> +static int ras2_register_pcc_channel(struct device *dev, struct ras2_scrub_ctx *ras2_ctx,
> +				     int pcc_subspace_id)
> +{
> +	struct acpi_pcct_hw_reduced *ras2_ss;
> +	struct mbox_client *ras2_mbox_cl;
> +	struct pcc_mbox_chan *pcc_chan;
> +	struct ras2_pcc_subspace *pcc_subspace;
> +
> +	if (pcc_subspace_id < 0)
> +		return -EINVAL;
> +
> +	mutex_lock(&ras2_pcc_subspace_lock);
> +	list_for_each_entry(pcc_subspace, &ras2_pcc_subspaces, elem) {
> +		if (pcc_subspace->pcc_subspace_id == pcc_subspace_id) {
> +			ras2_ctx->pcc_subspace = pcc_subspace;
> +			pcc_subspace->ref_count++;
> +			mutex_unlock(&ras2_pcc_subspace_lock);
> +			return 0;
> +		}
> +	}
> +	mutex_unlock(&ras2_pcc_subspace_lock);
> +
> +	pcc_subspace = kcalloc(1, sizeof(*pcc_subspace), GFP_KERNEL);
> +	if (!pcc_subspace)
> +		return -ENOMEM;
> +	pcc_subspace->pcc_subspace_id = pcc_subspace_id;
> +	ras2_mbox_cl = &pcc_subspace->mbox_client;
> +	ras2_mbox_cl->dev = dev;
> +	ras2_mbox_cl->knows_txdone = true;
> +
> +	pcc_chan = pcc_mbox_request_channel(ras2_mbox_cl, pcc_subspace_id);
> +	if (IS_ERR(pcc_chan)) {
> +		kfree(pcc_subspace);
> +		return PTR_ERR(pcc_chan);
> +	}
> +	pcc_subspace->pcc_chan = pcc_chan;
> +	ras2_ss = pcc_chan->mchan->con_priv;
> +	pcc_subspace->comm_base_addr = ras2_ss->base_address;
> +
> +	/*
> +	 * ras2_ss->latency is just a Nominal value. In reality
> +	 * the remote processor could be much slower to reply.
> +	 * So add an arbitrary amount of wait on top of Nominal.
> +	 */
> +	pcc_subspace->deadline = ns_to_ktime(RAS2_NUM_RETRIES * ras2_ss->latency *
> +					     NSEC_PER_USEC);
> +	pcc_subspace->pcc_mrtt = ras2_ss->min_turnaround_time;
> +	pcc_subspace->pcc_mpar = ras2_ss->max_access_rate;
> +	pcc_subspace->pcc_comm_addr = acpi_os_ioremap(pcc_subspace->comm_base_addr,
> +						      ras2_ss->length);
> +	/* Set flag so that we dont come here for each CPU. */
> +	pcc_subspace->pcc_channel_acquired = true;
> +
> +	mutex_lock(&ras2_pcc_subspace_lock);
> +	list_add(&pcc_subspace->elem, &ras2_pcc_subspaces);
> +	pcc_subspace->ref_count++;
> +	mutex_unlock(&ras2_pcc_subspace_lock);
> +	ras2_ctx->pcc_subspace = pcc_subspace;
> +
> +	return 0;
> +}
> +
> +static void ras2_unregister_pcc_channel(void *ctx)
> +{
> +	struct ras2_scrub_ctx *ras2_ctx = ctx;
> +	struct ras2_pcc_subspace *pcc_subspace = ras2_ctx->pcc_subspace;
> +
> +	if (!pcc_subspace  || !pcc_subspace->pcc_chan)
> +		return;
> +
> +	guard(mutex)(&ras2_pcc_subspace_lock);
> +	if (pcc_subspace->ref_count > 0)
> +		pcc_subspace->ref_count--;
> +	if (!pcc_subspace->ref_count) {
> +		list_del(&pcc_subspace->elem);
> +		pcc_mbox_free_channel(pcc_subspace->pcc_chan);
> +		kfree(pcc_subspace);
> +	}
> +}
> +
> +/**
> + * devm_ras2_register_pcc_channel() - Register RAS2 PCC channel
> + * @dev:		pointer to the RAS2 device
> + * @ras2_ctx:		pointer to the RAS2 context structure
> + * @pcc_subspace_id:	identifier of the RAS2 PCC channel.
> + *
> + * Returns: 0 on success, an error otherwise
> + */
> +int devm_ras2_register_pcc_channel(struct device *dev, struct ras2_scrub_ctx *ras2_ctx,
> +				   int pcc_subspace_id)
> +{
> +	int ret;
> +
> +	ret = ras2_register_pcc_channel(dev, ras2_ctx, pcc_subspace_id);
> +	if (ret)
> +		return ret;
> +
> +	return devm_add_action_or_reset(dev, ras2_unregister_pcc_channel, ras2_ctx);
> +}
> +EXPORT_SYMBOL_NS_GPL(devm_ras2_register_pcc_channel, ACPI_RAS2);
> +
> +static struct platform_device *ras2_add_platform_device(char *name, int channel)
> +{
> +	int ret;
> +	struct platform_device *pdev __free(platform_device_put) =
> +		platform_device_alloc(name, PLATFORM_DEVID_AUTO);
> +	if (!pdev)
> +		return ERR_PTR(-ENOMEM);
> +
> +	ret = platform_device_add_data(pdev, &channel, sizeof(channel));
> +	if (ret)
> +		return ERR_PTR(ret);
> +
> +	ret = platform_device_add(pdev);
> +	if (ret)
> +		return ERR_PTR(ret);
> +
> +	return_ptr(pdev);
> +}
> +
> +static int __init ras2_acpi_init(void)
> +{
> +	struct acpi_table_header *pAcpiTable = NULL;
> +	struct acpi_ras2_pcc_desc *pcc_desc_list;
> +	struct acpi_table_ras2 *pRas2Table;
> +	struct platform_device *pdev;
> +	int pcc_subspace_id;
> +	acpi_size ras2_size;
> +	acpi_status status;
> +	u8 count = 0, i;
> +	int ret;
> +
> +	status = acpi_get_table("RAS2", 0, &pAcpiTable);
> +	if (ACPI_FAILURE(status) || !pAcpiTable) {
> +		pr_err("ACPI RAS2 driver failed to initialize, get table failed\n");
> +		return -EINVAL;
> +	}
> +
> +	ras2_size = pAcpiTable->length;
> +	if (ras2_size < sizeof(struct acpi_table_ras2)) {
> +		pr_err("ACPI RAS2 table present but broken (too short #1)\n");
> +		ret = -EINVAL;
> +		goto free_ras2_table;
> +	}
> +
> +	pRas2Table = (struct acpi_table_ras2 *)pAcpiTable;
> +	if (pRas2Table->num_pcc_descs <= 0) {
> +		pr_err("ACPI RAS2 table does not contain PCC descriptors\n");
> +		ret = -EINVAL;
> +		goto free_ras2_table;
> +	}
> +
> +	struct platform_device **pdev_list __free(kfree) =
> +			kcalloc(pRas2Table->num_pcc_descs, sizeof(*pdev_list),
> +				GFP_KERNEL);
> +	if (!pdev_list) {
> +		ret = -ENOMEM;
> +		goto free_ras2_table;
> +	}
> +
> +	pcc_desc_list = (struct acpi_ras2_pcc_desc *)(pRas2Table + 1);
> +	/* Double scan for the case of only one actual controller */
> +	pcc_subspace_id = -1;
> +	count = 0;
> +	for (i = 0; i < pRas2Table->num_pcc_descs; i++, pcc_desc_list++) {
> +		if (pcc_desc_list->feature_type != RAS2_FEATURE_TYPE_MEMORY)
> +			continue;
> +		if (pcc_subspace_id == -1) {
> +			pcc_subspace_id = pcc_desc_list->channel_id;
> +			count++;
> +		}
> +		if (pcc_desc_list->channel_id != pcc_subspace_id)
> +			count++;
> +	}
> +	if (count == 1) {
> +		pdev = ras2_add_platform_device("acpi_ras2", pcc_subspace_id);
> +		if (!pdev) {
> +			ret = -ENODEV;
> +			goto free_ras2_pdev;
> +		}
> +		pdev_list[0] = pdev;
> +		return 0;
> +	}
> +
> +	count = 0;
> +	for (i = 0; i < pRas2Table->num_pcc_descs; i++, pcc_desc_list++) {
> +		if (pcc_desc_list->feature_type != RAS2_FEATURE_TYPE_MEMORY)
> +			continue;
> +		pcc_subspace_id = pcc_desc_list->channel_id;
> +		/* Add the platform device and bind ACPI RAS2 memory driver */
> +		pdev = ras2_add_platform_device("acpi_ras2", pcc_subspace_id);
> +		if (!pdev)
> +			goto free_ras2_pdev;
> +		pdev_list[count++] = pdev;
> +	}
> +
> +	acpi_put_table(pAcpiTable);
> +	return 0;
> +
> +free_ras2_pdev:
> +	for (i = count; i >= 0; i++)
> +		platform_device_put(pdev_list[i]);
> +
> +free_ras2_table:
> +	acpi_put_table(pAcpiTable);
> +
> +	return ret;
> +}
> +late_initcall(ras2_acpi_init)
> diff --git a/include/acpi/ras2_acpi.h b/include/acpi/ras2_acpi.h
> new file mode 100644
> index 000000000000..edfca253d88a
> --- /dev/null
> +++ b/include/acpi/ras2_acpi.h
> @@ -0,0 +1,60 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * RAS2 ACPI driver header file
> + *
> + * (C) Copyright 2014, 2015 Hewlett-Packard Enterprises
> + *
> + * Copyright (c) 2024 HiSilicon Limited
> + */
> +
> +#ifndef _RAS2_ACPI_H
> +#define _RAS2_ACPI_H
> +
> +#include <linux/acpi.h>
> +#include <linux/mailbox_client.h>
> +#include <linux/mutex.h>
> +#include <linux/types.h>
> +
> +#define RAS2_PCC_CMD_COMPLETE	BIT(0)
> +#define RAS2_PCC_CMD_ERROR	BIT(2)
> +
> +/* RAS2 specific PCC commands */
> +#define RAS2_PCC_CMD_EXEC 0x01
> +
> +struct device;
> +
> +/* Data structures for PCC communication and RAS2 table */
> +struct pcc_mbox_chan;
> +
> +struct ras2_pcc_subspace {
> +	int pcc_subspace_id;
> +	struct mbox_client mbox_client;
> +	struct pcc_mbox_chan *pcc_chan;
> +	struct acpi_ras2_shared_memory __iomem *pcc_comm_addr;
> +	u64 comm_base_addr;
> +	bool pcc_channel_acquired;
> +	ktime_t deadline;
> +	unsigned int pcc_mpar;
> +	unsigned int pcc_mrtt;
> +	struct list_head elem;
> +	u16 ref_count;
> +};

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