platform/x86/amd/pmf: Use ring buffer to store custom BIOS input values

Custom BIOS input values can be updated by multiple sources, such as power
mode changes and sensor events, each triggering a custom BIOS input event.
When these events occur in rapid succession, new data may overwrite
previous values before they are processed, resulting in lost updates.

To address this, introduce a fixed-size, power-of-two ring buffer to
capture every custom BIOS input event, storing both the pending request
and its associated input values. Access to the ring buffer is synchronized
using a mutex.

The previous use of memset() to clear the pending request structure after
each event is removed, as each BIOS input value is now copied into the
buffer as a snapshot. Consumers now process entries directly from the ring
buffer, making explicit clearing of the pending request structure
unnecessary.

Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>
Tested-by: Yijun Shen <Yijun.Shen@Dell.com>
Co-developed-by: Patil Rajesh Reddy <Patil.Reddy@amd.com>
Signed-off-by: Patil Rajesh Reddy <Patil.Reddy@amd.com>
Signed-off-by: Shyam Sundar S K <Shyam-sundar.S-k@amd.com>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://patch.msgid.link/20251202042219.245173-1-Shyam-sundar.S-k@amd.com
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

drivers/platform/x86/amd/pmf/acpi.c

@@ -9,6 +9,9 @@
  */
 
 #include <linux/acpi.h>
+#include <linux/array_size.h>
+#include <linux/cleanup.h>
+#include <linux/dev_printk.h>
 #include "pmf.h"
 
 #define APMF_CQL_NOTIFICATION  2
@@ -331,6 +334,39 @@ int apmf_get_sbios_requests(struct amd_pmf_dev *pdev, struct apmf_sbios_req *req
 									 req, sizeof(*req));
 }
 
+/* Store custom BIOS inputs data in ring buffer */
+static void amd_pmf_custom_bios_inputs_rb(struct amd_pmf_dev *pmf_dev)
+{
+	struct pmf_cbi_ring_buffer *rb = &pmf_dev->cbi_buf;
+	int i;
+
+	guard(mutex)(&pmf_dev->cbi_mutex);
+
+	switch (pmf_dev->cpu_id) {
+	case AMD_CPU_ID_PS:
+		for (i = 0; i < ARRAY_SIZE(custom_bios_inputs_v1); i++)
+			rb->data[rb->head].val[i] = pmf_dev->req1.custom_policy[i];
+		rb->data[rb->head].preq = pmf_dev->req1.pending_req;
+		break;
+	case PCI_DEVICE_ID_AMD_1AH_M20H_ROOT:
+	case PCI_DEVICE_ID_AMD_1AH_M60H_ROOT:
+		for (i = 0; i < ARRAY_SIZE(custom_bios_inputs); i++)
+			rb->data[rb->head].val[i] = pmf_dev->req.custom_policy[i];
+		rb->data[rb->head].preq = pmf_dev->req.pending_req;
+		break;
+	default:
+		return;
+	}
+
+	if (CIRC_SPACE(rb->head, rb->tail, CUSTOM_BIOS_INPUT_RING_ENTRIES) == 0) {
+		/* Rare case: ensures the newest BIOS input value is kept */
+		dev_warn(pmf_dev->dev, "Overwriting BIOS input value, data may be lost\n");
+		rb->tail = (rb->tail + 1) & (CUSTOM_BIOS_INPUT_RING_ENTRIES - 1);
+	}
+
+	rb->head = (rb->head + 1) & (CUSTOM_BIOS_INPUT_RING_ENTRIES - 1);
+}
+
 static void amd_pmf_handle_early_preq(struct amd_pmf_dev *pdev)
 {
 	if (!pdev->cb_flag)
@@ -356,6 +392,8 @@ static void apmf_event_handler_v2(acpi_handle handle, u32 event, void *data)
 	dev_dbg(pmf_dev->dev, "Pending request (preq): 0x%x\n", pmf_dev->req.pending_req);
 
 	amd_pmf_handle_early_preq(pmf_dev);
+
+	amd_pmf_custom_bios_inputs_rb(pmf_dev);
 }
 
 static void apmf_event_handler_v1(acpi_handle handle, u32 event, void *data)
@@ -374,6 +412,8 @@ static void apmf_event_handler_v1(acpi_handle handle, u32 event, void *data)
 	dev_dbg(pmf_dev->dev, "Pending request (preq1): 0x%x\n", pmf_dev->req1.pending_req);
 
 	amd_pmf_handle_early_preq(pmf_dev);
+
+	amd_pmf_custom_bios_inputs_rb(pmf_dev);
 }
 
 static void apmf_event_handler(acpi_handle handle, u32 event, void *data)

drivers/platform/x86/amd/pmf/core.c

@@ -11,6 +11,7 @@
 #include <linux/debugfs.h>
 #include <linux/iopoll.h>
 #include <linux/module.h>
+#include <linux/mutex.h>
 #include <linux/pci.h>
 #include <linux/platform_device.h>
 #include <linux/power_supply.h>
@@ -477,6 +478,10 @@ static int amd_pmf_probe(struct platform_device *pdev)
 	if (err)
 		return err;
 
+	err = devm_mutex_init(dev->dev, &dev->cbi_mutex);
+	if (err)
+		return err;
+
 	apmf_acpi_init(dev);
 	platform_set_drvdata(pdev, dev);
 	amd_pmf_dbgfs_register(dev);

drivers/platform/x86/amd/pmf/pmf.h

@@ -12,7 +12,9 @@
 #define PMF_H
 
 #include <linux/acpi.h>
+#include <linux/circ_buf.h>
 #include <linux/input.h>
+#include <linux/mutex_types.h>
 #include <linux/platform_device.h>
 #include <linux/platform_profile.h>
 
@@ -120,6 +122,7 @@ struct cookie_header {
 #define APTS_MAX_STATES		16
 #define CUSTOM_BIOS_INPUT_BITS	GENMASK(16, 7)
 #define BIOS_INPUTS_MAX		10
+#define CUSTOM_BIOS_INPUT_RING_ENTRIES	64	/* Must be power of two for CIRC_* macros */
 
 /* amd_pmf_send_cmd() set/get */
 #define SET_CMD		false
@@ -365,6 +368,22 @@ struct pmf_bios_inputs_prev {
 	u32 custom_bios_inputs[BIOS_INPUTS_MAX];
 };
 
+/**
+ * struct pmf_bios_input_entry - Snapshot of custom BIOS input event
+ * @val: Array of custom BIOS input values
+ * @preq: Pending request value associated with this event
+ */
+struct pmf_bios_input_entry {
+	u32 val[BIOS_INPUTS_MAX];
+	u32 preq;
+};
+
+struct pmf_cbi_ring_buffer {
+	struct pmf_bios_input_entry data[CUSTOM_BIOS_INPUT_RING_ENTRIES];
+	int head;
+	int tail;
+};
+
 struct amd_pmf_dev {
 	void __iomem *regbase;
 	void __iomem *smu_virt_addr;
@@ -413,6 +432,8 @@ struct amd_pmf_dev {
 	struct apmf_sbios_req_v1 req1;
 	struct pmf_bios_inputs_prev cb_prev; /* To preserve custom BIOS inputs */
 	bool cb_flag;			     /* To handle first custom BIOS input */
+	struct pmf_cbi_ring_buffer cbi_buf;
+	struct mutex cbi_mutex;		     /* Protects ring buffer access */
 };
 
 struct apmf_sps_prop_granular_v2 {

drivers/platform/x86/amd/pmf/spc.c

@@ -11,6 +11,7 @@
 
 #include <acpi/button.h>
 #include <linux/amd-pmf-io.h>
+#include <linux/cleanup.h>
 #include <linux/power_supply.h>
 #include <linux/units.h>
 #include "pmf.h"
@@ -132,32 +133,39 @@ static void amd_pmf_set_ta_custom_bios_input(struct ta_pmf_enact_table *in, int
 	}
 }
 
-static void amd_pmf_update_bios_inputs(struct amd_pmf_dev *pdev, u32 pending_req,
+static void amd_pmf_update_bios_inputs(struct amd_pmf_dev *pdev, struct pmf_bios_input_entry *data,
 				       const struct amd_pmf_pb_bitmap *inputs,
-				       const u32 *custom_policy, struct ta_pmf_enact_table *in)
+				       struct ta_pmf_enact_table *in)
 {
 	unsigned int i;
 
 	for (i = 0; i < ARRAY_SIZE(custom_bios_inputs); i++) {
-		if (!(pending_req & inputs[i].bit_mask))
+		if (!(data->preq & inputs[i].bit_mask))
 			continue;
-		amd_pmf_set_ta_custom_bios_input(in, i, custom_policy[i]);
-		pdev->cb_prev.custom_bios_inputs[i] = custom_policy[i];
-		dev_dbg(pdev->dev, "Custom BIOS Input[%d]: %u\n", i, custom_policy[i]);
+		amd_pmf_set_ta_custom_bios_input(in, i, data->val[i]);
+		pdev->cb_prev.custom_bios_inputs[i] = data->val[i];
+		dev_dbg(pdev->dev, "Custom BIOS Input[%d]: %u\n", i, data->val[i]);
 	}
 }
 
 static void amd_pmf_get_custom_bios_inputs(struct amd_pmf_dev *pdev,
 					   struct ta_pmf_enact_table *in)
 {
+	struct pmf_cbi_ring_buffer *rb = &pdev->cbi_buf;
 	unsigned int i;
 
+	guard(mutex)(&pdev->cbi_mutex);
+
 	for (i = 0; i < ARRAY_SIZE(custom_bios_inputs); i++)
 		amd_pmf_set_ta_custom_bios_input(in, i, pdev->cb_prev.custom_bios_inputs[i]);
 
-	if (!(pdev->req.pending_req || pdev->req1.pending_req))
+	if (CIRC_CNT(rb->head, rb->tail, CUSTOM_BIOS_INPUT_RING_ENTRIES) == 0)
 		return;
 
+	/* If no active custom BIOS input pending request, do not consume further work */
+	if (!rb->data[rb->tail].preq)
+		goto out_rbadvance;
+
 	if (!pdev->smart_pc_enabled)
 		return;
 
@@ -165,20 +173,17 @@ static void amd_pmf_get_custom_bios_inputs(struct amd_pmf_dev *pdev,
 	case PMF_IF_V1:
 		if (!is_apmf_bios_input_notifications_supported(pdev))
 			return;
-		amd_pmf_update_bios_inputs(pdev, pdev->req1.pending_req, custom_bios_inputs_v1,
-					   pdev->req1.custom_policy, in);
+		amd_pmf_update_bios_inputs(pdev, &rb->data[rb->tail], custom_bios_inputs_v1, in);
 		break;
 	case PMF_IF_V2:
-		amd_pmf_update_bios_inputs(pdev, pdev->req.pending_req, custom_bios_inputs,
-					   pdev->req.custom_policy, in);
+		amd_pmf_update_bios_inputs(pdev, &rb->data[rb->tail], custom_bios_inputs, in);
 		break;
 	default:
 		break;
 	}
 
-	/* Clear pending requests after handling */
-	memset(&pdev->req, 0, sizeof(pdev->req));
-	memset(&pdev->req1, 0, sizeof(pdev->req1));
+out_rbadvance:
+	rb->tail = (rb->tail + 1) & (CUSTOM_BIOS_INPUT_RING_ENTRIES - 1);
 }
 
 static void amd_pmf_get_c0_residency(u16 *core_res, size_t size, struct ta_pmf_enact_table *in)

drivers/platform/x86/amd/pmf/tee-if.c

@@ -591,6 +591,8 @@ int amd_pmf_init_smart_pc(struct amd_pmf_dev *dev)
 		status = ret == TA_PMF_TYPE_SUCCESS;
 		if (status) {
 			dev->cb_flag = true;
+			dev->cbi_buf.head = 0;
+			dev->cbi_buf.tail = 0;
 			break;
 		}
 		amd_pmf_tee_deinit(dev);