From b0d4bb973539f5e60fff37ea0f211598cac614a8 Mon Sep 17 00:00:00 2001
From: Shyam Sundar S K <Shyam-sundar.S-k@amd.com>
Date: Mon, 6 Feb 2023 20:38:53 +0530
Subject: [PATCH] platform/x86/amd: pmc: Write dummy postcode into the STB DRAM
Git-commit: b0d4bb973539f5e60fff37ea0f211598cac614a8
Patch-mainline: v6.3-rc1
References: bsc#1210644

Based on the recommendation from the PMFW team in order to get the
recent telemetry data present on the STB DRAM the driver is required
to send one dummy write to the STB buffer, so it internally triggers
the PMFW to emit the latest telemetry data in the STB DRAM region.

Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Shyam Sundar S K <Shyam-sundar.S-k@amd.com>
Link: https://lore.kernel.org/r/20230206150855.1938810-3-Shyam-sundar.S-k@amd.com
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/platform/x86/amd/pmc.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/drivers/platform/x86/amd/pmc.c
+++ b/drivers/platform/x86/amd/pmc.c
@@ -42,6 +42,7 @@
 #define AMD_PMC_STB_PMI_0		0x03E30600
 #define AMD_PMC_STB_S2IDLE_PREPARE	0xC6000001
 #define AMD_PMC_STB_S2IDLE_RESTORE	0xC6000002
+#define AMD_PMC_STB_DUMMY_PC		0xC6000007
 
 /* STB S2D(Spill to DRAM) has different message port offset */
 #define STB_SPILL_TO_DRAM		0xBE
@@ -249,6 +250,11 @@ static int amd_pmc_stb_debugfs_open_v2(s
 	u32 *buf, fsize, num_samples, stb_rdptr_offset = 0;
 	int ret;
 
+	/* Write dummy postcode while reading the STB buffer */
+	ret = amd_pmc_write_stb(dev, AMD_PMC_STB_DUMMY_PC);
+	if (ret)
+		dev_err(dev->dev, "error writing to STB: %d\n", ret);
+
 	buf = kzalloc(S2D_TELEMETRY_BYTES_MAX, GFP_KERNEL);
 	if (!buf)
 		return -ENOMEM;