linux-kernel - Re: [PATCH 05/17] drm/msm/a6xx: Fix PDC sleep sequence

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Message-ID: <937197e9-09dd-4f3c-bdb4-4001f5217c07@oss.qualcomm.com>
Date: Thu, 7 Aug 2025 15:51:02 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Akhil P Oommen <akhilpo@....qualcomm.com>,
        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>
Cc: linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 05/17] drm/msm/a6xx: Fix PDC sleep sequence

On 7/20/25 2:16 PM, Akhil P Oommen wrote:
> Since the PDC resides out of the GPU subsystem and cannot be reset in
> case it enters bad state, utmost care must be taken to trigger the PDC
> wake/sleep routines in the correct order.
> 
> The PDC wake sequence can be exercised only after a PDC sleep sequence.
> Additionally, GMU firmware should initialize a few registers before the
> KMD can trigger a PDC sleep sequence. So PDC sleep can't be done if the
> GMU firmware has not initialized. Track these dependencies using a new
> status variable and trigger PDC sleep/wake sequences appropriately.
> 
> Signed-off-by: Akhil P Oommen <akhilpo@....qualcomm.com>
> ---

FWIW some time ago I made this patch, which tackles a similar issue,
perhaps it's a good idea to merge both:

>From 7d6441fc6ec5ee7fe723e1ad86d11fdd17bee922 Mon Sep 17 00:00:00 2001
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
Date: Thu, 20 Feb 2025 10:28:51 +0100
Subject: [PATCH] drm/msm/adreno: Delay the Adreno RPMh startup to HFI init

There's no use in trying to power up the GX logic before we're almost
ready to fire up the GPU. In fact, with A8xx the PDC and RSC uCode are
loaded by the GMU firmware, so we *must* wait for the GMU to fully
initialize before trying to do so.

Move it to right before HFI init.

Signed-off-by: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
---
 drivers/gpu/drm/msm/adreno/a6xx_gmu.c | 12 ++----------
 drivers/gpu/drm/msm/adreno/a6xx_gmu.h |  1 +
 drivers/gpu/drm/msm/adreno/a6xx_hfi.c |  2 +-
 3 files changed, 4 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gmu.c b/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
index 28e6705c6da6..3335583ada45 100644
--- a/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
+++ b/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
@@ -513,7 +513,7 @@ static int a6xx_gmu_notify_slumber(struct a6xx_gmu *gmu)
 	return ret;
 }
 
-static int a6xx_rpmh_start(struct a6xx_gmu *gmu)
+int a6xx_rpmh_start(struct a6xx_gmu *gmu)
 {
 	int ret;
 	u32 val;
@@ -842,19 +842,11 @@ static int a6xx_gmu_fw_start(struct a6xx_gmu *gmu, unsigned int state)
 	else
 		gmu_write(gmu, REG_A6XX_GMU_GENERAL_7, 1);
 
-	if (state == GMU_WARM_BOOT) {
-		ret = a6xx_rpmh_start(gmu);
-		if (ret)
-			return ret;
-	} else {
+	if (state == GMU_COLD_BOOT) {
 		if (WARN(!adreno_gpu->fw[ADRENO_FW_GMU],
 			"GMU firmware is not loaded\n"))
 			return -ENOENT;
 
-		ret = a6xx_rpmh_start(gmu);
-		if (ret)
-			return ret;
-
 		ret = a6xx_gmu_fw_load(gmu);
 		if (ret)
 			return ret;
diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gmu.h b/drivers/gpu/drm/msm/adreno/a6xx_gmu.h
index d1ce11131ba6..309305298a45 100644
--- a/drivers/gpu/drm/msm/adreno/a6xx_gmu.h
+++ b/drivers/gpu/drm/msm/adreno/a6xx_gmu.h
@@ -216,5 +216,6 @@ bool a6xx_gmu_gx_is_on(struct a6xx_gmu *gmu);
 bool a6xx_gmu_sptprac_is_on(struct a6xx_gmu *gmu);
 void a6xx_sptprac_disable(struct a6xx_gmu *gmu);
 int a6xx_sptprac_enable(struct a6xx_gmu *gmu);
+int a6xx_rpmh_start(struct a6xx_gmu *gmu);
 
 #endif
diff --git a/drivers/gpu/drm/msm/adreno/a6xx_hfi.c b/drivers/gpu/drm/msm/adreno/a6xx_hfi.c
index 8e69b1e84657..9ea01daf2995 100644
--- a/drivers/gpu/drm/msm/adreno/a6xx_hfi.c
+++ b/drivers/gpu/drm/msm/adreno/a6xx_hfi.c
@@ -910,7 +910,7 @@ int a6xx_hfi_start(struct a6xx_gmu *gmu, int boot_state)
 	if (ret)
 		return ret;
 
-	return 0;
+	return a6xx_rpmh_start(gmu);
 }
 
 void a6xx_hfi_stop(struct a6xx_gmu *gmu)
-- 
2.50.1



Konrad