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

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Message-ID: <0a81938b-f30e-fa78-fd73-c753af4e324b@quicinc.com>
Date:   Wed, 3 Aug 2022 15:45:40 +0530
From:   Akhil P Oommen <quic_akhilpo@...cinc.com>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        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 8/2/2022 12:44 PM, Dmitry Baryshkov wrote:
> 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?
I can't see any issue with a race here. reset_control_reset() will 
return immediately in that case.

-Akhil.
>
>> +
>>       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)
>
>