linux-kernel - [PATCH v2 06/16] drm/msm: Add an ftrace for gpu register access

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Message-Id: <20250908-ifpc-support-v2-6-631b1080bf91@oss.qualcomm.com>
Date: Mon, 08 Sep 2025 13:56:59 +0530
From: Akhil P Oommen <akhilpo@....qualcomm.com>
To: Rob Clark <robin.clark@....qualcomm.com>, Sean Paul <sean@...rly.run>,
        Konrad Dybcio <konradybcio@...nel.org>,
        Dmitry Baryshkov <lumag@...nel.org>,
        Abhinav Kumar <abhinav.kumar@...ux.dev>,
        Jessica Zhang <jessica.zhang@....qualcomm.com>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        Antonino Maniscalco <antomani103@...il.com>,
        Neil Armstrong <neil.armstrong@...aro.org>
Cc: linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Akhil P Oommen <akhilpo@....qualcomm.com>
Subject: [PATCH v2 06/16] drm/msm: Add an ftrace for gpu register access

With IFPC, there is a probability of accessing a GX domain register when
it is collapsed, which leads to gmu fence errors. To debug this, we need
to trace every gpu register accesses and identify the one just before a
gmu fence error. So, add an ftrace to track all gpu register accesses.

Signed-off-by: Akhil P Oommen <akhilpo@....qualcomm.com>
---
 drivers/gpu/drm/msm/msm_gpu.h       |  8 ++++++++
 drivers/gpu/drm/msm/msm_gpu_trace.h | 12 ++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/drivers/gpu/drm/msm/msm_gpu.h b/drivers/gpu/drm/msm/msm_gpu.h
index b2a96544f92a55cdb372729498b8f0b0f9ca80bd..866bb090af064666586cea7125254bd375b7a35c 100644
--- a/drivers/gpu/drm/msm/msm_gpu.h
+++ b/drivers/gpu/drm/msm/msm_gpu.h
@@ -16,6 +16,7 @@
 
 #include "msm_drv.h"
 #include "msm_fence.h"
+#include "msm_gpu_trace.h"
 #include "msm_ringbuffer.h"
 #include "msm_gem.h"
 
@@ -613,16 +614,19 @@ struct msm_gpu_state {
 
 static inline void gpu_write(struct msm_gpu *gpu, u32 reg, u32 data)
 {
+	trace_msm_gpu_regaccess(reg);
 	writel(data, gpu->mmio + (reg << 2));
 }
 
 static inline u32 gpu_read(struct msm_gpu *gpu, u32 reg)
 {
+	trace_msm_gpu_regaccess(reg);
 	return readl(gpu->mmio + (reg << 2));
 }
 
 static inline void gpu_rmw(struct msm_gpu *gpu, u32 reg, u32 mask, u32 or)
 {
+	trace_msm_gpu_regaccess(reg);
 	msm_rmw(gpu->mmio + (reg << 2), mask, or);
 }
 
@@ -644,7 +648,9 @@ static inline u64 gpu_read64(struct msm_gpu *gpu, u32 reg)
 	 * when the lo is read, so make sure to read the lo first to trigger
 	 * that
 	 */
+	trace_msm_gpu_regaccess(reg);
 	val = (u64) readl(gpu->mmio + (reg << 2));
+	trace_msm_gpu_regaccess(reg+1);
 	val |= ((u64) readl(gpu->mmio + ((reg + 1) << 2)) << 32);
 
 	return val;
@@ -652,8 +658,10 @@ static inline u64 gpu_read64(struct msm_gpu *gpu, u32 reg)
 
 static inline void gpu_write64(struct msm_gpu *gpu, u32 reg, u64 val)
 {
+	trace_msm_gpu_regaccess(reg);
 	/* Why not a writeq here? Read the screed above */
 	writel(lower_32_bits(val), gpu->mmio + (reg << 2));
+	trace_msm_gpu_regaccess(reg+1);
 	writel(upper_32_bits(val), gpu->mmio + ((reg + 1) << 2));
 }
 
diff --git a/drivers/gpu/drm/msm/msm_gpu_trace.h b/drivers/gpu/drm/msm/msm_gpu_trace.h
index 781bbe5540bde6d9cd6758050229fd0406fad232..5417f8d389a370e8d0b9c7e447050e2965011c0a 100644
--- a/drivers/gpu/drm/msm/msm_gpu_trace.h
+++ b/drivers/gpu/drm/msm/msm_gpu_trace.h
@@ -219,6 +219,18 @@ TRACE_EVENT(msm_mmu_prealloc_cleanup,
 		TP_printk("count=%u, remaining=%u", __entry->count, __entry->remaining)
 );
 
+TRACE_EVENT(msm_gpu_regaccess,
+		TP_PROTO(u32 offset),
+		TP_ARGS(offset),
+		TP_STRUCT__entry(
+			__field(u32, offset)
+			),
+		TP_fast_assign(
+			__entry->offset = offset;
+			),
+		TP_printk("offset=0x%x", __entry->offset)
+);
+
 #endif
 
 #undef TRACE_INCLUDE_PATH

-- 
2.50.1