[v2,2/3] ACPI:RAS2: Add ACPI RAS2 driver

Commit Message

Shiju Jose March 5, 2025, 6:02 p.m. UTC

From: Shiju Jose <[e-mail]>

Add support for ACPI RAS2 feature table (RAS2) defined in the
ACPI 6.5 Specification, section 5.2.21.
Driver defines RAS2 Init, which extracts the RAS2 table and driver
adds auxiliary 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.

Acked-by: Rafael J. Wysocki <[e-mail]>
Co-developed-by: A Somasundaram <[e-mail]>
Signed-off-by: A Somasundaram <[e-mail]>
Co-developed-by: Jonathan Cameron <[e-mail]>
Signed-off-by: Jonathan Cameron <[e-mail]>
Tested-by: Daniel Ferguson <[e-mail]>
Signed-off-by: Shiju Jose <[e-mail]>
---
 drivers/acpi/Kconfig  |  11 ++
 drivers/acpi/Makefile |   1 +
 drivers/acpi/bus.c    |   3 +
 drivers/acpi/ras2.c   | 416 ++++++++++++++++++++++++++++++++++++++++++
 include/acpi/ras2.h   |  48 +++++
 5 files changed, 479 insertions(+)
 create mode 100755 drivers/acpi/ras2.c
 create mode 100644 include/acpi/ras2.h

Comments

Jonathan Cameron March 6, 2025, 9:19 a.m. UTC | #1

On Wed, 5 Mar 2025 18:02:23 +0000
<[e-mail]> wrote:

> From: Shiju Jose <[e-mail]>
> 
> Add support for ACPI RAS2 feature table (RAS2) defined in the
> ACPI 6.5 Specification, section 5.2.21.
> Driver defines RAS2 Init, which extracts the RAS2 table and driver
> adds auxiliary 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.
> 
> Acked-by: Rafael J. Wysocki <[e-mail]>
> Co-developed-by: A Somasundaram <[e-mail]>
> Signed-off-by: A Somasundaram <[e-mail]>
> Co-developed-by: Jonathan Cameron <[e-mail]>
> Signed-off-by: Jonathan Cameron <[e-mail]>
> Tested-by: Daniel Ferguson <[e-mail]>
> Signed-off-by: Shiju Jose <[e-mail]>

Hi Shiju,

I took another look through as it's been a while and I've
pretty much forgotten this code :(

Anyhow, a few minor comments inline.

Thanks,

Jonathan

> diff --git a/drivers/acpi/ras2.c b/drivers/acpi/ras2.c
> new file mode 100755
> index 000000000000..8831a2bd5fab
> --- /dev/null
> +++ b/drivers/acpi/ras2.c




> +static int ras2_register_pcc_channel(struct ras2_mem_ctx *ras2_ctx, int pcc_id)
> +{
> +	struct ras2_pcc_subspace *pcc_subspace;
> +	struct pcc_mbox_chan *pcc_chan;
> +	struct mbox_client *mbox_cl;
> +
> +	if (pcc_id < 0)
> +		return -EINVAL;
> +
> +	mutex_lock(&ras2_pcc_lock);
> +	list_for_each_entry(pcc_subspace, &ras2_pcc_subspaces, elem) {
> +		if (pcc_subspace->pcc_id != pcc_id)
> +			continue;
> +		ras2_ctx->pcc_subspace = pcc_subspace;
> +		pcc_subspace->ref_count++;
> +		mutex_unlock(&ras2_pcc_lock);
> +		return 0;
> +	}
> +	mutex_unlock(&ras2_pcc_lock);
> +
> +	pcc_subspace = kcalloc(1, sizeof(*pcc_subspace), GFP_KERNEL);

if allocating a count of 1, why not kzalloc?

> +	if (!pcc_subspace)
> +		return -ENOMEM;




> +static int acpi_ras2_parse(void)
> +{
> +	struct acpi_ras2_pcc_desc *pcc_desc_list;
> +	int pcc_id;
> +	u8 count = 0;
> +	int rc, i;
> +
> +	if (ras2_tab->header.length  < sizeof(struct acpi_table_ras2)) {

extra space before <

Maybe sizeof(*ras2_tab) is cleaner.

> +		pr_warn(FW_WARN "ACPI RAS2 table present but broken (too short #1)\n");
> +		return -EINVAL;
> +	}
> +
> +	if (!ras2_tab->num_pcc_descs) {
> +		pr_warn(FW_WARN "No PCC descs in ACPI RAS2 table\n");
> +		return -EINVAL;
> +	}
> +
> +	pcc_desc_list = (struct acpi_ras2_pcc_desc *)(ras2_tab + 1);
> +	/* Double scan for the case of only one actual controller */
> +	pcc_id = -1;
> +	count = 0;

Already set above, so no need to do it again.  I'd do it just here.  Can
put it in the loop init though.

> +	for (i = 0; i < ras2_tab->num_pcc_descs; i++, pcc_desc_list++) {
> +		if (pcc_desc_list->feature_type != RAS2_FEAT_TYPE_MEMORY)
> +			continue;
> +		if (pcc_id == -1) {
> +			pcc_id = pcc_desc_list->channel_id;
> +			count++;
> +		}
> +		if (pcc_desc_list->channel_id != pcc_id)
> +			count++;
> +	}
> +
> +	/*
> +	 * Workaround for the client platform with multiple scrub devices
> +	 * but uses single PCC subspace for communication.
> +	 */
> +	if (count == 1) {
> +		/* Add auxiliary device and bind ACPI RAS2 memory driver */
> +		rc = ras2_add_aux_device(RAS2_MEM_DEV_ID_NAME, pcc_id);
> +		if (rc)
> +			return rc;
> +
> +		return 0;
> +	}
> +
> +	pcc_desc_list = (struct acpi_ras2_pcc_desc *)(ras2_tab + 1);
> +	count = 0;

Maybe set in loop init.

> +	for (i = 0; i < ras2_tab->num_pcc_descs; i++, pcc_desc_list++) {
> +		if (pcc_desc_list->feature_type != RAS2_FEAT_TYPE_MEMORY)
> +			continue;
> +		pcc_id = pcc_desc_list->channel_id;
> +		/* Add auxiliary device and bind ACPI RAS2 memory driver */
obvious enough to drop the comment I think.

> +		rc = ras2_add_aux_device(RAS2_MEM_DEV_ID_NAME, pcc_id);
					 pcc_desc_list->channel_id);
and no local variable.

> +		if (rc)
> +			return rc;
> +	}
> +
> +	return 0;
> +}
> +
> +void __init acpi_ras2_init(void)
> +{
> +	acpi_status status;
> +	int rc;
> +
> +	status = acpi_get_table(ACPI_SIG_RAS2, 0,
> +				(struct acpi_table_header **)&ras2_tab);
> +	if (ACPI_FAILURE(status) || !ras2_tab) {
> +		const char *msg = acpi_format_exception(status);
> +
> +		pr_err("Failed to get table, %s\n", msg);

If only going to use it here maybe
		pr_err("Failed to get table, %s\n",
		       acpi_format_exception(status));
and save on the local variable.

> +		return;
> +	}
> +
> +	rc = acpi_ras2_parse();
> +	if (rc) {
> +		acpi_put_table((struct acpi_table_header *)ras2_tab); 
> +		pr_err("Failed to parse RAS2 table\n");
> +	}
> +}
> diff --git a/include/acpi/ras2.h b/include/acpi/ras2.h
> new file mode 100644
> index 000000000000..5b27c1f30096
> --- /dev/null
> +++ b/include/acpi/ras2.h
> @@ -0,0 +1,48 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * ACPI RAS2 driver header file
> + *
> + * Copyright (c) 2024-2025 HiSilicon Limited
> + */
> +
> +#ifndef _ACPI_RAS2_H
> +#define _ACPI_RAS2_H
> +
> +#include <linux/acpi.h>
> +#include <linux/auxiliary_bus.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)
> +
I think these bits are from table 14.11 and
generic to all PCC status registers? Should these
have more generic names rather than ras2 specific ones?

> +/* RAS2 specific PCC commands */
> +#define RAS2_PCC_CMD_EXEC 0x01
Are we mixing commands and field definitions both
with prefix RAS2_PCC_CMD_ ?  That is somewhat
confusing. 

> +
> +#define RAS2_AUX_DEV_NAME "ras2"
> +#define RAS2_MEM_DEV_ID_NAME "acpi_ras2_mem"
> +
I would add a forwards def
struct device;  

whilst it is really unlikely that headers would ever be reorganized
such that auxiliary_bus.h would not include device.h given the embedded
device we shouldn't rely on that here.

> +/* Data structure RAS2 table */
> +struct ras2_mem_ctx {
> +	struct auxiliary_device adev;
> +	/* Lock to provide mutually exclusive access to PCC channel */
> +	struct mutex lock;
> +	struct device *dev;
> +	struct acpi_ras2_shmem __iomem *comm_addr;
> +	void *pcc_subspace;
> +	int id;
> +};
> +
> +#ifdef CONFIG_ACPI_RAS2
> +void __init acpi_ras2_init(void);
> +int ras2_send_pcc_cmd(struct ras2_mem_ctx *ras2_ctx, u16 cmd);
> +#else
> +static inline void acpi_ras2_init(void) { }
> +
> +static inline int ras2_send_pcc_cmd(struct ras2_mem_ctx *ras2_ctx, u16 cmd)

Is this stub ever needed?  To me it seems unlikely
we would have a user that is built without a dependency
on CONFIG_ACPI_RAS2.  This is different from acpi_ras2_init()
which makes much more sense to me.

> +{
> +	return -EOPNOTSUPP;
> +}
> +#endif
> +#endif /* _ACPI_RAS2_H */

Shiju Jose March 6, 2025, 11:21 a.m. UTC | #2

>-----Original Message-----
>From: Jonathan Cameron <[e-mail]>
>Sent: 06 March 2025 09:19
>To: Shiju Jose <[e-mail]>
>Cc: [e-mail]; [e-mail]; [e-mail];
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>[e-mail]; [e-mail]; [e-mail]; linux-
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>[e-mail]; [e-mail];
>[e-mail]; [e-mail]; tanxiaofei
><[e-mail]>; Zengtao (B) <[e-mail]>; Roberto
>Sassu <[e-mail]>; [e-mail];
>wanghuiqiang <[e-mail]>; Linuxarm
><[e-mail]>
>Subject: Re: [PATCH v2 2/3] ACPI:RAS2: Add ACPI RAS2 driver
>
>On Wed, 5 Mar 2025 18:02:23 +0000
><[e-mail]> wrote:
>
>> From: Shiju Jose <[e-mail]>
>>
>> Add support for ACPI RAS2 feature table (RAS2) defined in the ACPI 6.5
>> Specification, section 5.2.21.
>> Driver defines RAS2 Init, which extracts the RAS2 table and driver
>> adds auxiliary 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.
>>
>> Acked-by: Rafael J. Wysocki <[e-mail]>
>> Co-developed-by: A Somasundaram <[e-mail]>
>> Signed-off-by: A Somasundaram <[e-mail]>
>> Co-developed-by: Jonathan Cameron <[e-mail]>
>> Signed-off-by: Jonathan Cameron <[e-mail]>
>> Tested-by: Daniel Ferguson <[e-mail]>
>> Signed-off-by: Shiju Jose <[e-mail]>
>
>Hi Shiju,
>
>I took another look through as it's been a while and I've pretty much forgotten
>this code :(
>
>Anyhow, a few minor comments inline.

Hi Jonathan,

Thanks for the feedbacks.

Please find reply inline.

Thanks,
Shiju
>
>Thanks,
>
>Jonathan
>
>> diff --git a/drivers/acpi/ras2.c b/drivers/acpi/ras2.c new file mode
>> 100755 index 000000000000..8831a2bd5fab
>> --- /dev/null
>> +++ b/drivers/acpi/ras2.c
>
>
>
>
>> +static int ras2_register_pcc_channel(struct ras2_mem_ctx *ras2_ctx, int
>pcc_id)
>> +{
>> +	struct ras2_pcc_subspace *pcc_subspace;
>> +	struct pcc_mbox_chan *pcc_chan;
>> +	struct mbox_client *mbox_cl;
>> +
>> +	if (pcc_id < 0)
>> +		return -EINVAL;
>> +
>> +	mutex_lock(&ras2_pcc_lock);
>> +	list_for_each_entry(pcc_subspace, &ras2_pcc_subspaces, elem) {
>> +		if (pcc_subspace->pcc_id != pcc_id)
>> +			continue;
>> +		ras2_ctx->pcc_subspace = pcc_subspace;
>> +		pcc_subspace->ref_count++;
>> +		mutex_unlock(&ras2_pcc_lock);
>> +		return 0;
>> +	}
>> +	mutex_unlock(&ras2_pcc_lock);
>> +
>> +	pcc_subspace = kcalloc(1, sizeof(*pcc_subspace), GFP_KERNEL);
>
>if allocating a count of 1, why not kzalloc?

Will use kzalloc.
>
>> +	if (!pcc_subspace)
>> +		return -ENOMEM;
>
>
>
>
>> +static int acpi_ras2_parse(void)
>> +{
>> +	struct acpi_ras2_pcc_desc *pcc_desc_list;
>> +	int pcc_id;
>> +	u8 count = 0;
>> +	int rc, i;
>> +
>> +	if (ras2_tab->header.length  < sizeof(struct acpi_table_ras2)) {
>
>extra space before <

Will fix. 
>
>Maybe sizeof(*ras2_tab) is cleaner.
Sure.
>
>> +		pr_warn(FW_WARN "ACPI RAS2 table present but broken (too
>short #1)\n");
>> +		return -EINVAL;
>> +	}
>> +
>> +	if (!ras2_tab->num_pcc_descs) {
>> +		pr_warn(FW_WARN "No PCC descs in ACPI RAS2 table\n");
>> +		return -EINVAL;
>> +	}
>> +
>> +	pcc_desc_list = (struct acpi_ras2_pcc_desc *)(ras2_tab + 1);
>> +	/* Double scan for the case of only one actual controller */
>> +	pcc_id = -1;
>> +	count = 0;
>
>Already set above, so no need to do it again.  I'd do it just here.  Can
>put it in the loop init though.
Will change.
>
>> +	for (i = 0; i < ras2_tab->num_pcc_descs; i++, pcc_desc_list++) {
>> +		if (pcc_desc_list->feature_type != RAS2_FEAT_TYPE_MEMORY)
>> +			continue;
>> +		if (pcc_id == -1) {
>> +			pcc_id = pcc_desc_list->channel_id;
>> +			count++;
>> +		}
>> +		if (pcc_desc_list->channel_id != pcc_id)
>> +			count++;
>> +	}
>> +
>> +	/*
>> +	 * Workaround for the client platform with multiple scrub devices
>> +	 * but uses single PCC subspace for communication.
>> +	 */
>> +	if (count == 1) {
>> +		/* Add auxiliary device and bind ACPI RAS2 memory driver */
>> +		rc = ras2_add_aux_device(RAS2_MEM_DEV_ID_NAME, pcc_id);
>> +		if (rc)
>> +			return rc;
>> +
>> +		return 0;
>> +	}
>> +
>> +	pcc_desc_list = (struct acpi_ras2_pcc_desc *)(ras2_tab + 1);
>> +	count = 0;
>
>Maybe set in loop init.
Sure.
>
>> +	for (i = 0; i < ras2_tab->num_pcc_descs; i++, pcc_desc_list++) {
>> +		if (pcc_desc_list->feature_type != RAS2_FEAT_TYPE_MEMORY)
>> +			continue;
>> +		pcc_id = pcc_desc_list->channel_id;
>> +		/* Add auxiliary device and bind ACPI RAS2 memory driver */
>obvious enough to drop the comment I think.
Will do.
>
>> +		rc = ras2_add_aux_device(RAS2_MEM_DEV_ID_NAME, pcc_id);
>					 pcc_desc_list->channel_id);
>and no local variable.
Ok.
>
>> +		if (rc)
>> +			return rc;
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>> +void __init acpi_ras2_init(void)
>> +{
>> +	acpi_status status;
>> +	int rc;
>> +
>> +	status = acpi_get_table(ACPI_SIG_RAS2, 0,
>> +				(struct acpi_table_header **)&ras2_tab);
>> +	if (ACPI_FAILURE(status) || !ras2_tab) {
>> +		const char *msg = acpi_format_exception(status);
>> +
>> +		pr_err("Failed to get table, %s\n", msg);
>
>If only going to use it here maybe
>		pr_err("Failed to get table, %s\n",
>		       acpi_format_exception(status));
>and save on the local variable.
Will change.
>
>> +		return;
>> +	}
>> +
>> +	rc = acpi_ras2_parse();
>> +	if (rc) {
>> +		acpi_put_table((struct acpi_table_header *)ras2_tab);
>> +		pr_err("Failed to parse RAS2 table\n");
>> +	}
>> +}
>> diff --git a/include/acpi/ras2.h b/include/acpi/ras2.h
>> new file mode 100644
>> index 000000000000..5b27c1f30096
>> --- /dev/null
>> +++ b/include/acpi/ras2.h
>> @@ -0,0 +1,48 @@
>> +/* SPDX-License-Identifier: GPL-2.0-only */
>> +/*
>> + * ACPI RAS2 driver header file
>> + *
>> + * Copyright (c) 2024-2025 HiSilicon Limited
>> + */
>> +
>> +#ifndef _ACPI_RAS2_H
>> +#define _ACPI_RAS2_H
>> +
>> +#include <linux/acpi.h>
>> +#include <linux/auxiliary_bus.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)
>> +
>I think these bits are from table 14.11 and
>generic to all PCC status registers? Should these
>have more generic names rather than ras2 specific ones?
Yes.
Instead will use PCC_STATUS_CMD_ COMPLETE and  PCC_STATUS_ ERROR
from include/acpi/pcc.h. 

>
>> +/* RAS2 specific PCC commands */
>> +#define RAS2_PCC_CMD_EXEC 0x01
>Are we mixing commands and field definitions both
>with prefix RAS2_PCC_CMD_ ?  That is somewhat
>confusing.
Will add Table 5.82: .. here in the comment and 
Is rename to PCC_CMD_ EXEC_RAS2  better?
>
>> +
>> +#define RAS2_AUX_DEV_NAME "ras2"
>> +#define RAS2_MEM_DEV_ID_NAME "acpi_ras2_mem"
>> +
>I would add a forwards def
>struct device;
Sure.
>
>whilst it is really unlikely that headers would ever be reorganized
>such that auxiliary_bus.h would not include device.h given the embedded
>device we shouldn't rely on that here.
>
>> +/* Data structure RAS2 table */
>> +struct ras2_mem_ctx {
>> +	struct auxiliary_device adev;
>> +	/* Lock to provide mutually exclusive access to PCC channel */
>> +	struct mutex lock;
>> +	struct device *dev;
>> +	struct acpi_ras2_shmem __iomem *comm_addr;
>> +	void *pcc_subspace;
>> +	int id;
>> +};
>> +
>> +#ifdef CONFIG_ACPI_RAS2
>> +void __init acpi_ras2_init(void);
>> +int ras2_send_pcc_cmd(struct ras2_mem_ctx *ras2_ctx, u16 cmd);
>> +#else
>> +static inline void acpi_ras2_init(void) { }
>> +
>> +static inline int ras2_send_pcc_cmd(struct ras2_mem_ctx *ras2_ctx, u16
>cmd)
>
>Is this stub ever needed?  To me it seems unlikely
>we would have a user that is built without a dependency
>on CONFIG_ACPI_RAS2.  This is different from acpi_ras2_init()
>which makes much more sense to me.
Ok will remove.
>
>> +{
>> +	return -EOPNOTSUPP;
>> +}
>> +#endif
>> +#endif /* _ACPI_RAS2_H */

Thanks,
Shiju

Patch

diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
index d81b55f5068c..bae9a47c829d 100644
--- a/drivers/acpi/Kconfig
+++ b/drivers/acpi/Kconfig
@@ -293,6 +293,17 @@  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 AUXILIARY_BUS
+	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 40208a0f5dfb..797b38cdc2f3 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/bus.c b/drivers/acpi/bus.c
index 058910af82bc..9a0a1582b8c3 100644
--- a/drivers/acpi/bus.c
+++ b/drivers/acpi/bus.c
@@ -29,6 +29,7 @@ 
 #include <linux/acpi_viot.h>
 #include <linux/pci.h>
 #include <acpi/apei.h>
+#include <acpi/ras2.h>
 #include <linux/suspend.h>
 #include <linux/prmt.h>
 
@@ -1472,6 +1473,8 @@  static int __init acpi_init(void)
 	acpi_debugger_init();
 	acpi_setup_sb_notify_handler();
 	acpi_viot_init();
+	acpi_ras2_init();
+
 	return 0;
 }
 
diff --git a/drivers/acpi/ras2.c b/drivers/acpi/ras2.c
new file mode 100755
index 000000000000..8831a2bd5fab
--- /dev/null
+++ b/drivers/acpi/ras2.c
@@ -0,0 +1,416 @@ 
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Implementation of ACPI RAS2 driver.
+ *
+ * Copyright (c) 2024-2025 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 <acpi/pcc.h>
+#include <acpi/ras2.h>
+
+static struct acpi_table_ras2 *__read_mostly ras2_tab;
+
+/* Data structure for PCC communication */
+struct ras2_pcc_subspace {
+	int pcc_id;
+	struct mbox_client mbox_client;
+	struct pcc_mbox_chan *pcc_chan;
+	struct acpi_ras2_shmem __iomem *comm_addr;
+	bool pcc_chnl_acq;
+	ktime_t deadline;
+	unsigned int pcc_mpar;
+	unsigned int pcc_mrtt;
+	struct list_head elem;
+	u16 ref_count;
+};
+
+/*
+ * Arbitrary Retries for PCC commands because the
+ * remote processor could be much slower to reply.
+ */
+#define RAS2_NUM_RETRIES 600
+
+#define RAS2_FEAT_TYPE_MEMORY        0x00
+
+/* Global variables for the RAS2 PCC subspaces */
+static DEFINE_MUTEX(ras2_pcc_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_shmem __iomem *gen_comm_base = pcc_subspace->comm_addr;
+	ktime_t next_deadline = ktime_add(ktime_get(), pcc_subspace->deadline);
+	u32 cap_status;
+	u16 status;
+	u32 rc;
+
+	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(&gen_comm_base->status);
+		if (status & RAS2_PCC_CMD_ERROR) {
+			cap_status = readw_relaxed(&gen_comm_base->set_caps_status);
+			rc = ras2_report_cap_error(cap_status);
+
+			status &= ~RAS2_PCC_CMD_ERROR;
+			writew_relaxed(status, &gen_comm_base->status);
+			return rc;
+		}
+
+		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_mem_ctx *ras2_ctx, u16 cmd)
+{
+	struct ras2_pcc_subspace *pcc_subspace = ras2_ctx->pcc_subspace;
+	struct acpi_ras2_shmem *gen_comm_base = pcc_subspace->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 rc;
+
+	guard(mutex)(&ras2_pcc_lock);
+	rc = ras2_check_pcc_chan(pcc_subspace);
+	if (rc < 0)
+		return rc;
+
+	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, &gen_comm_base->cmd);
+
+	/* Flip CMD COMPLETE bit */
+	writew_relaxed(0, &gen_comm_base->status);
+
+	/* Ring doorbell */
+	rc = mbox_send_message(pcc_channel, &cmd);
+	if (rc < 0) {
+		dev_err(ras2_ctx->dev,
+			"Err sending PCC mbox message. cmd:%d, rc:%d\n",
+			cmd, rc);
+		return rc;
+	}
+
+	/*
+	 * 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) {
+		rc = 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, rc);
+	else
+		mbox_client_txdone(pcc_channel, rc);
+
+	return rc >= 0 ? 0 : rc;
+}
+EXPORT_SYMBOL_GPL(ras2_send_pcc_cmd);
+
+static int ras2_register_pcc_channel(struct ras2_mem_ctx *ras2_ctx, int pcc_id)
+{
+	struct ras2_pcc_subspace *pcc_subspace;
+	struct pcc_mbox_chan *pcc_chan;
+	struct mbox_client *mbox_cl;
+
+	if (pcc_id < 0)
+		return -EINVAL;
+
+	mutex_lock(&ras2_pcc_lock);
+	list_for_each_entry(pcc_subspace, &ras2_pcc_subspaces, elem) {
+		if (pcc_subspace->pcc_id != pcc_id)
+			continue;
+		ras2_ctx->pcc_subspace = pcc_subspace;
+		pcc_subspace->ref_count++;
+		mutex_unlock(&ras2_pcc_lock);
+		return 0;
+	}
+	mutex_unlock(&ras2_pcc_lock);
+
+	pcc_subspace = kcalloc(1, sizeof(*pcc_subspace), GFP_KERNEL);
+	if (!pcc_subspace)
+		return -ENOMEM;
+
+	mbox_cl = &pcc_subspace->mbox_client;
+	mbox_cl->knows_txdone = true;
+
+	pcc_chan = pcc_mbox_request_channel(mbox_cl, pcc_id);
+	if (IS_ERR(pcc_chan)) {
+		kfree(pcc_subspace);
+		return PTR_ERR(pcc_chan);
+	}
+
+	*pcc_subspace = (struct ras2_pcc_subspace) {
+		.pcc_id = pcc_id,
+		.pcc_chan = pcc_chan,
+		.comm_addr = acpi_os_ioremap(pcc_chan->shmem_base_addr,
+					     pcc_chan->shmem_size),
+		.deadline = ns_to_ktime(RAS2_NUM_RETRIES *
+					pcc_chan->latency *
+					NSEC_PER_USEC),
+		.pcc_mrtt = pcc_chan->min_turnaround_time,
+		.pcc_mpar = pcc_chan->max_access_rate,
+		.mbox_client = {
+			.knows_txdone = true,
+		},
+		.pcc_chnl_acq = true,
+	};
+
+	mutex_lock(&ras2_pcc_lock);
+	list_add(&pcc_subspace->elem, &ras2_pcc_subspaces);
+	pcc_subspace->ref_count++;
+	mutex_unlock(&ras2_pcc_lock);
+	ras2_ctx->pcc_subspace = pcc_subspace;
+	ras2_ctx->comm_addr = pcc_subspace->comm_addr;
+	ras2_ctx->dev = pcc_chan->mchan->mbox->dev;
+
+	return 0;
+}
+
+static DEFINE_IDA(ras2_ida);
+static void ras2_remove_pcc(struct ras2_mem_ctx *ras2_ctx)
+{
+	struct ras2_pcc_subspace *pcc_subspace = ras2_ctx->pcc_subspace;
+
+	guard(mutex)(&ras2_pcc_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);
+	}
+}
+
+static void ras2_release(struct device *device)
+{
+	struct auxiliary_device *auxdev = container_of(device, struct auxiliary_device, dev);
+	struct ras2_mem_ctx *ras2_ctx = container_of(auxdev, struct ras2_mem_ctx, adev);
+
+	ida_free(&ras2_ida, auxdev->id);
+	ras2_remove_pcc(ras2_ctx);
+	kfree(ras2_ctx);
+}
+
+static int ras2_add_aux_device(char *name, int channel)
+{
+	struct ras2_mem_ctx *ras2_ctx;
+	int id, rc;
+
+	ras2_ctx = kzalloc(sizeof(*ras2_ctx), GFP_KERNEL);
+	if (!ras2_ctx)
+		return -ENOMEM;
+
+	mutex_init(&ras2_ctx->lock);
+
+	rc = ras2_register_pcc_channel(ras2_ctx, channel);
+	if (rc < 0) {
+		pr_debug("failed to register pcc channel rc=%d\n", rc);
+		goto ctx_free;
+	}
+
+	id = ida_alloc(&ras2_ida, GFP_KERNEL);
+	if (id < 0) {
+		rc = id;
+		goto pcc_free;
+	}
+
+	ras2_ctx->id = id;
+	ras2_ctx->adev.id = id;
+	ras2_ctx->adev.name = RAS2_MEM_DEV_ID_NAME;
+	ras2_ctx->adev.dev.release = ras2_release;
+	ras2_ctx->adev.dev.parent = ras2_ctx->dev;
+
+	rc = auxiliary_device_init(&ras2_ctx->adev);
+	if (rc)
+		goto ida_free;
+
+	rc = auxiliary_device_add(&ras2_ctx->adev);
+	if (rc) {
+		auxiliary_device_uninit(&ras2_ctx->adev);
+		return rc;
+	}
+
+	return 0;
+
+ida_free:
+	ida_free(&ras2_ida, id);
+pcc_free:
+	ras2_remove_pcc(ras2_ctx);
+ctx_free:
+	kfree(ras2_ctx);
+
+	return rc;
+}
+
+static int acpi_ras2_parse(void)
+{
+	struct acpi_ras2_pcc_desc *pcc_desc_list;
+	int pcc_id;
+	u8 count = 0;
+	int rc, i;
+
+	if (ras2_tab->header.length  < sizeof(struct acpi_table_ras2)) {
+		pr_warn(FW_WARN "ACPI RAS2 table present but broken (too short #1)\n");
+		return -EINVAL;
+	}
+
+	if (!ras2_tab->num_pcc_descs) {
+		pr_warn(FW_WARN "No PCC descs in ACPI RAS2 table\n");
+		return -EINVAL;
+	}
+
+	pcc_desc_list = (struct acpi_ras2_pcc_desc *)(ras2_tab + 1);
+	/* Double scan for the case of only one actual controller */
+	pcc_id = -1;
+	count = 0;
+	for (i = 0; i < ras2_tab->num_pcc_descs; i++, pcc_desc_list++) {
+		if (pcc_desc_list->feature_type != RAS2_FEAT_TYPE_MEMORY)
+			continue;
+		if (pcc_id == -1) {
+			pcc_id = pcc_desc_list->channel_id;
+			count++;
+		}
+		if (pcc_desc_list->channel_id != pcc_id)
+			count++;
+	}
+
+	/*
+	 * Workaround for the client platform with multiple scrub devices
+	 * but uses single PCC subspace for communication.
+	 */
+	if (count == 1) {
+		/* Add auxiliary device and bind ACPI RAS2 memory driver */
+		rc = ras2_add_aux_device(RAS2_MEM_DEV_ID_NAME, pcc_id);
+		if (rc)
+			return rc;
+
+		return 0;
+	}
+
+	pcc_desc_list = (struct acpi_ras2_pcc_desc *)(ras2_tab + 1);
+	count = 0;
+	for (i = 0; i < ras2_tab->num_pcc_descs; i++, pcc_desc_list++) {
+		if (pcc_desc_list->feature_type != RAS2_FEAT_TYPE_MEMORY)
+			continue;
+		pcc_id = pcc_desc_list->channel_id;
+		/* Add auxiliary device and bind ACPI RAS2 memory driver */
+		rc = ras2_add_aux_device(RAS2_MEM_DEV_ID_NAME, pcc_id);
+		if (rc)
+			return rc;
+	}
+
+	return 0;
+}
+
+void __init acpi_ras2_init(void)
+{
+	acpi_status status;
+	int rc;
+
+	status = acpi_get_table(ACPI_SIG_RAS2, 0,
+				(struct acpi_table_header **)&ras2_tab);
+	if (ACPI_FAILURE(status) || !ras2_tab) {
+		const char *msg = acpi_format_exception(status);
+
+		pr_err("Failed to get table, %s\n", msg);
+		return;
+	}
+
+	rc = acpi_ras2_parse();
+	if (rc) {
+		acpi_put_table((struct acpi_table_header *)ras2_tab);
+		pr_err("Failed to parse RAS2 table\n");
+	}
+}
diff --git a/include/acpi/ras2.h b/include/acpi/ras2.h
new file mode 100644
index 000000000000..5b27c1f30096
--- /dev/null
+++ b/include/acpi/ras2.h
@@ -0,0 +1,48 @@ 
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * ACPI RAS2 driver header file
+ *
+ * Copyright (c) 2024-2025 HiSilicon Limited
+ */
+
+#ifndef _ACPI_RAS2_H
+#define _ACPI_RAS2_H
+
+#include <linux/acpi.h>
+#include <linux/auxiliary_bus.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
+
+#define RAS2_AUX_DEV_NAME "ras2"
+#define RAS2_MEM_DEV_ID_NAME "acpi_ras2_mem"
+
+/* Data structure RAS2 table */
+struct ras2_mem_ctx {
+	struct auxiliary_device adev;
+	/* Lock to provide mutually exclusive access to PCC channel */
+	struct mutex lock;
+	struct device *dev;
+	struct acpi_ras2_shmem __iomem *comm_addr;
+	void *pcc_subspace;
+	int id;
+};
+
+#ifdef CONFIG_ACPI_RAS2
+void __init acpi_ras2_init(void);
+int ras2_send_pcc_cmd(struct ras2_mem_ctx *ras2_ctx, u16 cmd);
+#else
+static inline void acpi_ras2_init(void) { }
+
+static inline int ras2_send_pcc_cmd(struct ras2_mem_ctx *ras2_ctx, u16 cmd)
+{
+	return -EOPNOTSUPP;
+}
+#endif
+#endif /* _ACPI_RAS2_H */