linux-kernel - Re: [PATCH v3 5/8] drm/msm/a6xx: Ensure CX collapse during gpu recovery

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Message-ID: <8715e07f-9d58-1ae3-9a3a-25828b545905@linaro.org>
Date:   Tue, 2 Aug 2022 10:14:09 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Akhil P Oommen <quic_akhilpo@...cinc.com>,
        freedreno <freedreno@...ts.freedesktop.org>,
        dri-devel@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
        Rob Clark <robdclark@...il.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     Jordan Crouse <jordan@...micpenguin.net>,
        Jonathan Marek <jonathan@...ek.ca>,
        Douglas Anderson <dianders@...omium.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Chia-I Wu <olvaffe@...il.com>, Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Sean Paul <sean@...rly.run>,
        Stephen Boyd <swboyd@...omium.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 5/8] drm/msm/a6xx: Ensure CX collapse during gpu
 recovery

On 30/07/2022 12:40, Akhil P Oommen wrote:
> Because there could be transient votes from other drivers/tz/hyp which
> may keep the cx gdsc enabled, we should poll until cx gdsc collapses.
> We can use the reset framework to poll for cx gdsc collapse from gpucc
> clk driver.
> 
> This feature requires support from the platform's gpucc driver.
> 
> Signed-off-by: Akhil P Oommen <quic_akhilpo@...cinc.com>
> ---
> 
> Changes in v3:
> - Use reset interface from gpucc driver to poll for cx gdsc collapse
>    https://patchwork.freedesktop.org/series/106860/
> 
>   drivers/gpu/drm/msm/adreno/a6xx_gpu.c | 4 ++++
>   drivers/gpu/drm/msm/msm_gpu.c         | 4 ++++
>   drivers/gpu/drm/msm/msm_gpu.h         | 4 ++++
>   3 files changed, 12 insertions(+)
> 
> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> index 1b049c5..721d5e6 100644
> --- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> @@ -10,6 +10,7 @@
>   
>   #include <linux/bitfield.h>
>   #include <linux/devfreq.h>
> +#include <linux/reset.h>
>   #include <linux/soc/qcom/llcc-qcom.h>
>   
>   #define GPU_PAS_ID 13
> @@ -1224,6 +1225,9 @@ static void a6xx_recover(struct msm_gpu *gpu)
>   	/* And the final one from recover worker */
>   	pm_runtime_put_sync(&gpu->pdev->dev);
>   
> +	/* Call into gpucc driver to poll for cx gdsc collapse */
> +	reset_control_reset(gpu->cx_collapse);

Do we have a race between the last pm_runtime_put_sync(), this polling 
and other voters removing their votes beforehand?

> +
>   	pm_runtime_use_autosuspend(&gpu->pdev->dev);
>   
>   	if (active_submits)
> diff --git a/drivers/gpu/drm/msm/msm_gpu.c b/drivers/gpu/drm/msm/msm_gpu.c
> index 07e55a6..4a57627 100644
> --- a/drivers/gpu/drm/msm/msm_gpu.c
> +++ b/drivers/gpu/drm/msm/msm_gpu.c
> @@ -14,6 +14,7 @@
>   #include <generated/utsrelease.h>
>   #include <linux/string_helpers.h>
>   #include <linux/devcoredump.h>
> +#include <linux/reset.h>
>   #include <linux/sched/task.h>
>   
>   /*
> @@ -903,6 +904,9 @@ int msm_gpu_init(struct drm_device *drm, struct platform_device *pdev,
>   	if (IS_ERR(gpu->gpu_cx))
>   		gpu->gpu_cx = NULL;
>   
> +	gpu->cx_collapse = devm_reset_control_get_optional(&pdev->dev,
> +			"cx_collapse");
> +
>   	gpu->pdev = pdev;
>   	platform_set_drvdata(pdev, &gpu->adreno_smmu);
>   
> diff --git a/drivers/gpu/drm/msm/msm_gpu.h b/drivers/gpu/drm/msm/msm_gpu.h
> index 6def008..ab59fd2 100644
> --- a/drivers/gpu/drm/msm/msm_gpu.h
> +++ b/drivers/gpu/drm/msm/msm_gpu.h
> @@ -13,6 +13,7 @@
>   #include <linux/interconnect.h>
>   #include <linux/pm_opp.h>
>   #include <linux/regulator/consumer.h>
> +#include <linux/reset.h>
>   
>   #include "msm_drv.h"
>   #include "msm_fence.h"
> @@ -268,6 +269,9 @@ struct msm_gpu {
>   	bool hw_apriv;
>   
>   	struct thermal_cooling_device *cooling;
> +
> +	/* To poll for cx gdsc collapse during gpu recovery */
> +	struct reset_control *cx_collapse;
>   };
>   
>   static inline struct msm_gpu *dev_to_gpu(struct device *dev)


-- 
With best wishes
Dmitry