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

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Message-Id: <20250720-ifpc-support-v1-5-9347aa5bcbd6@oss.qualcomm.com>
Date: Sun, 20 Jul 2025 17:46:06 +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>
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 05/17] drm/msm/a6xx: Fix PDC sleep sequence

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>
---
 drivers/gpu/drm/msm/adreno/a6xx_gmu.c | 30 +++++++++++++++++++-----------
 drivers/gpu/drm/msm/adreno/a6xx_gmu.h |  6 ++++++
 2 files changed, 25 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gmu.c b/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
index 3bebb6dd7059782ceca29f2efd2acee24d3fc930..4d6c70735e0892ed87d6a68d64f24bda844e5e16 100644
--- a/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
+++ b/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
@@ -279,6 +279,8 @@ static int a6xx_gmu_start(struct a6xx_gmu *gmu)
 	if (ret)
 		DRM_DEV_ERROR(gmu->dev, "GMU firmware initialization timed out\n");
 
+	set_bit(GMU_STATUS_FW_START, &gmu->status);
+
 	return ret;
 }
 
@@ -528,6 +530,9 @@ static int a6xx_rpmh_start(struct a6xx_gmu *gmu)
 	int ret;
 	u32 val;
 
+	if (!test_and_clear_bit(GMU_STATUS_PDC_SLEEP, &gmu->status))
+		return 0;
+
 	gmu_write(gmu, REG_A6XX_GMU_RSCC_CONTROL_REQ, BIT(1));
 
 	ret = gmu_poll_timeout(gmu, REG_A6XX_GMU_RSCC_CONTROL_ACK, val,
@@ -555,6 +560,11 @@ static void a6xx_rpmh_stop(struct a6xx_gmu *gmu)
 	int ret;
 	u32 val;
 
+	if (test_and_clear_bit(GMU_STATUS_FW_START, &gmu->status))
+		return;
+
+	/* TODO: should we skip if IFPC is not enabled */
+
 	gmu_write(gmu, REG_A6XX_GMU_RSCC_CONTROL_REQ, 1);
 
 	ret = gmu_poll_timeout_rscc(gmu, REG_A6XX_GPU_RSCC_RSC_STATUS0_DRV0,
@@ -563,6 +573,8 @@ static void a6xx_rpmh_stop(struct a6xx_gmu *gmu)
 		DRM_DEV_ERROR(gmu->dev, "Unable to power off the GPU RSC\n");
 
 	gmu_write(gmu, REG_A6XX_GMU_RSCC_CONTROL_REQ, 0);
+
+	set_bit(GMU_STATUS_PDC_SLEEP, &gmu->status);
 }
 
 static inline void pdc_write(void __iomem *ptr, u32 offset, u32 value)
@@ -691,8 +703,6 @@ static void a6xx_gmu_rpmh_init(struct a6xx_gmu *gmu)
 	/* ensure no writes happen before the uCode is fully written */
 	wmb();
 
-	a6xx_rpmh_stop(gmu);
-
 err:
 	if (!IS_ERR_OR_NULL(pdcptr))
 		iounmap(pdcptr);
@@ -852,19 +862,15 @@ 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 {
+	ret = a6xx_rpmh_start(gmu);
+	if (ret)
+		return ret;
+
+	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;
@@ -1046,6 +1052,8 @@ static void a6xx_gmu_force_off(struct a6xx_gmu *gmu)
 
 	/* Reset GPU core blocks */
 	a6xx_gpu_sw_reset(gpu, true);
+
+	a6xx_rpmh_stop(gmu);
 }
 
 static void a6xx_gmu_set_initial_freq(struct msm_gpu *gpu, struct a6xx_gmu *gmu)
diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gmu.h b/drivers/gpu/drm/msm/adreno/a6xx_gmu.h
index b2d4489b40249b1916ab4a42c89e3f4bdc5c4af9..034f1b4e5a3fb9cd601bfbe6d06d64e5ace3b6e7 100644
--- a/drivers/gpu/drm/msm/adreno/a6xx_gmu.h
+++ b/drivers/gpu/drm/msm/adreno/a6xx_gmu.h
@@ -117,6 +117,12 @@ struct a6xx_gmu {
 
 	struct qmp *qmp;
 	struct a6xx_hfi_msg_bw_table *bw_table;
+
+/* To check if we can trigger sleep seq at PDC. Cleared in a6xx_rpmh_stop() */
+#define GMU_STATUS_FW_START	0
+/* To track if PDC sleep seq was done */
+#define GMU_STATUS_PDC_SLEEP	1
+	unsigned long status;
 };
 
 static inline u32 gmu_read(struct a6xx_gmu *gmu, u32 offset)

-- 
2.50.1