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

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Message-ID: <acdff7a4-bd9f-45c1-b620-25e667d1f628@linaro.org>
Date: Tue, 12 Aug 2025 10:06:40 +0200
From: Neil Armstrong <neil.armstrong@...aro.org>
To: Dikshita Agarwal <quic_dikshita@...cinc.com>,
 Vikash Garodia <quic_vgarodia@...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
Subject: Re: [PATCH] media: iris: vpu3x: Add MNoC low power handshake during
 hardware power-off

On 12/08/2025 09:48, Dikshita Agarwal wrote:
> 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.
> 
> Signed-off-by: Dikshita Agarwal <quic_dikshita@...cinc.com>
> ---
>   drivers/media/platform/qcom/iris/iris_vpu3x.c | 23 +++++++++++++++++++++--
>   1 file changed, 21 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..c2e6af575cbe4b3e3f2a019b24eecf3a5d469566 100644
> --- a/drivers/media/platform/qcom/iris/iris_vpu3x.c
> +++ b/drivers/media/platform/qcom/iris/iris_vpu3x.c
> @@ -110,6 +110,7 @@ static void iris_vpu3_power_off_hardware(struct iris_core *core)
>   static void iris_vpu33_power_off_hardware(struct iris_core *core)
>   {
>   	u32 reg_val = 0, value, i;
> +	u32 count = 0;
>   	int ret;
>   
>   	if (iris_vpu3x_hw_power_collapsed(core))
> @@ -128,13 +129,31 @@ static void iris_vpu33_power_off_hardware(struct iris_core *core)
>   			goto disable_power;
>   	}
>   
> +	/* set MNoC to low power */
> +	writel(REQ_POWER_DOWN_PREP, core->reg_base + AON_WRAPPER_MVP_NOC_LPI_CONTROL);
> +
> +	value = readl(core->reg_base + AON_WRAPPER_MVP_NOC_LPI_STATUS);
> +
> +	while (!(value & BIT(0)) && (value & BIT(2) || value & BIT(1))) {
> +		writel(0, core->reg_base + AON_WRAPPER_MVP_NOC_LPI_CONTROL);
> +
> +		usleep_range(10, 20);
> +
> +		writel(REQ_POWER_DOWN_PREP, core->reg_base + AON_WRAPPER_MVP_NOC_LPI_CONTROL);
> +
> +		value = readl(core->reg_base + AON_WRAPPER_MVP_NOC_LPI_STATUS);
> +		if (++count >= 1000) {
> +			dev_err(core->dev, "LPI handshake timeout\n");
> +			break;
> +		}
> +	}
> +
>   	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,

Tested-by: Neil Armstrong <neil.armstrong@...aro.org> # on SM8650-HDK

Thanks,
Neil