linux-kernel - [PATCH v3] media: iris: vpu3x: Add MNoC low power handshake during hardware power-off

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Message-ID: <20250821-sm8650-power-sequence-fix-v3-1-645816ba3826@quicinc.com>
Date: Thu, 21 Aug 2025 16:24:38 +0530
From: Dikshita Agarwal <quic_dikshita@...cinc.com>
To: Vikash Garodia <quic_vgarodia@...cinc.com>,
        Dikshita Agarwal
	<quic_dikshita@...cinc.com>,
        Abhinav Kumar <abhinav.kumar@...ux.dev>,
        "Bryan
 O'Donoghue" <bryan.odonoghue@...aro.org>,
        Mauro Carvalho Chehab
	<mchehab@...nel.org>
CC: <linux-media@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        Neil Armstrong <neil.armstrong@...aro.org>
Subject: [PATCH v3] media: iris: vpu3x: Add MNoC low power handshake during
 hardware power-off

Add the missing write to AON_WRAPPER_MVP_NOC_LPI_CONTROL before
reading the LPI status register. Introduce a handshake loop to ensure
MNoC enters low power mode reliably during VPU3 hardware power-off with
timeout handling.

Tested-by: Neil Armstrong <neil.armstrong@...aro.org> # on SM8650-QRD
Tested-by: Neil Armstrong <neil.armstrong@...aro.org> # on SM8650-HDK
Signed-off-by: Dikshita Agarwal <quic_dikshita@...cinc.com>
---
Changes in v3:
- Fixed the loop to capture the  success of the last power-on command (Bryan)
- Link to v2: https://lore.kernel.org/r/20250813-sm8650-power-sequence-fix-v2-1-9ed0fc2c45cb@quicinc.com

Changes in v2:
- Restructured loop for readability (Jorge)
- Used defines for bits (Konrad, Jorge)
- Used udelay for short waits (Konrad)
- Link to v1: https://lore.kernel.org/r/20250812-sm8650-power-sequence-fix-v1-1-a51e7f99c56c@quicinc.com
---
 drivers/media/platform/qcom/iris/iris_vpu3x.c | 32 +++++++++++++++++++++++++--
 1 file changed, 30 insertions(+), 2 deletions(-)

diff --git a/drivers/media/platform/qcom/iris/iris_vpu3x.c b/drivers/media/platform/qcom/iris/iris_vpu3x.c
index 9b7c9a1495ee2f51c60b1142b2ed4680ff798f0a..bfc52eb04ed0e1c88efe74a8d27bb95e8a0ca331 100644
--- a/drivers/media/platform/qcom/iris/iris_vpu3x.c
+++ b/drivers/media/platform/qcom/iris/iris_vpu3x.c
@@ -19,6 +19,9 @@
 #define WRAPPER_IRIS_CPU_NOC_LPI_CONTROL	(WRAPPER_BASE_OFFS + 0x5C)
 #define REQ_POWER_DOWN_PREP			BIT(0)
 #define WRAPPER_IRIS_CPU_NOC_LPI_STATUS		(WRAPPER_BASE_OFFS + 0x60)
+#define NOC_LPI_STATUS_DONE			BIT(0) /* Indicates the NOC handshake is complete */
+#define NOC_LPI_STATUS_DENY			BIT(1) /* Indicates the NOC handshake is denied */
+#define NOC_LPI_STATUS_ACTIVE		BIT(2) /* Indicates the NOC is active */
 #define WRAPPER_CORE_CLOCK_CONFIG		(WRAPPER_BASE_OFFS + 0x88)
 #define CORE_CLK_RUN				0x0
 
@@ -109,7 +112,9 @@ static void iris_vpu3_power_off_hardware(struct iris_core *core)
 
 static void iris_vpu33_power_off_hardware(struct iris_core *core)
 {
+	bool handshake_done = false, handshake_busy = false;
 	u32 reg_val = 0, value, i;
+	u32 count = 0;
 	int ret;
 
 	if (iris_vpu3x_hw_power_collapsed(core))
@@ -128,13 +133,36 @@ static void iris_vpu33_power_off_hardware(struct iris_core *core)
 			goto disable_power;
 	}
 
+	/* Retry up to 1000 times as recommended by hardware documentation */
+	do {
+		/* set MNoC to low power */
+		writel(REQ_POWER_DOWN_PREP, core->reg_base + AON_WRAPPER_MVP_NOC_LPI_CONTROL);
+
+		udelay(15);
+
+		value = readl(core->reg_base + AON_WRAPPER_MVP_NOC_LPI_STATUS);
+
+		handshake_done = value & NOC_LPI_STATUS_DONE;
+		handshake_busy = value & (NOC_LPI_STATUS_DENY | NOC_LPI_STATUS_ACTIVE);
+
+		if (handshake_done || !handshake_busy)
+			break;
+
+		writel(0, core->reg_base + AON_WRAPPER_MVP_NOC_LPI_CONTROL);
+
+		udelay(15);
+
+	} while (++count < 1000);
+
+	if (!handshake_done && handshake_busy)
+		dev_err(core->dev, "LPI handshake timeout\n");
+
 	ret = readl_poll_timeout(core->reg_base + AON_WRAPPER_MVP_NOC_LPI_STATUS,
 				 reg_val, reg_val & BIT(0), 200, 2000);
 	if (ret)
 		goto disable_power;
 
-	/* set MNoC to low power, set PD_NOC_QREQ (bit 0) */
-	writel(BIT(0), core->reg_base + AON_WRAPPER_MVP_NOC_LPI_CONTROL);
+	writel(0, core->reg_base + AON_WRAPPER_MVP_NOC_LPI_CONTROL);
 
 	writel(CORE_BRIDGE_SW_RESET | CORE_BRIDGE_HW_RESET_DISABLE,
 	       core->reg_base + CPU_CS_AHB_BRIDGE_SYNC_RESET);

---
base-commit: d968e50b5c26642754492dea23cbd3592bde62d8
change-id: 20250812-sm8650-power-sequence-fix-ba9a92098233

Best regards,
-- 
Dikshita Agarwal <quic_dikshita@...cinc.com>