Message-ID: <9d037933-6d55-9a4b-f3e4-8993816c4425@quicinc.com>
Date:   Mon, 10 Jul 2023 09:18:22 -0700
From:   Kuogee Hsieh <quic_khsieh@...cinc.com>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        <dri-devel@...ts.freedesktop.org>, <robdclark@...il.com>,
        <sean@...rly.run>, <swboyd@...omium.org>, <dianders@...omium.org>,
        <vkoul@...nel.org>, <daniel@...ll.ch>, <airlied@...il.com>,
        <agross@...nel.org>, <andersson@...nel.org>
CC:     <quic_abhinavk@...cinc.com>, <quic_jesszhan@...cinc.com>,
        <quic_sbillaka@...cinc.com>, <marijn.suijten@...ainline.org>,
        <freedreno@...ts.freedesktop.org>, <linux-arm-msm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 2/5] drm/msm/dp: incorporate pm_runtime framework into
 DP driver


On 7/7/2023 5:04 PM, Dmitry Baryshkov wrote:
> On 08/07/2023 02:52, Kuogee Hsieh wrote:
>> Incorporating pm runtime framework into DP driver so that power
>> and clock resource handling can be centralized allowing easier
>> control of these resources in preparation of registering aux bus
>> uring probe.
>>
>> Signed-off-by: Kuogee Hsieh <quic_khsieh@...cinc.com>
>> ---
>>   drivers/gpu/drm/msm/dp/dp_aux.c     |  3 ++
>>   drivers/gpu/drm/msm/dp/dp_display.c | 75 
>> +++++++++++++++++++++++++++++--------
>>   2 files changed, 63 insertions(+), 15 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/msm/dp/dp_aux.c 
>> b/drivers/gpu/drm/msm/dp/dp_aux.c
>> index 8e3b677..c592064 100644
>> --- a/drivers/gpu/drm/msm/dp/dp_aux.c
>> +++ b/drivers/gpu/drm/msm/dp/dp_aux.c
>> @@ -291,6 +291,7 @@ static ssize_t dp_aux_transfer(struct drm_dp_aux 
>> *dp_aux,
>>           return -EINVAL;
>>       }
>>   +    pm_runtime_get_sync(dp_aux->dev);
>
> Let me quote the function's documentation:
> Consider using pm_runtime_resume_and_get() instead of it, especially 
> if its return value is checked by the caller, as this is likely to 
> result in cleaner code.

pm_runtime_resume_and_get() will call pm_runtime_resume()  every time.

Since aux_transfer is called very frequently, is it just simple to call 
pm_runtiem_get_sync() which will call pm_runtime_reusme() if power 
counter is 0 before increased it.

otherwise it just increase power counter?


>
> So two notes concerning the whole patch:
> - error checking is missing
> - please use pm_runtime_resume_and_get() instead.
>
>>       mutex_lock(&aux->mutex);
>>       if (!aux->initted) {
>>           ret = -EIO;
>> @@ -364,6 +365,8 @@ static ssize_t dp_aux_transfer(struct drm_dp_aux 
>> *dp_aux,
>>     exit:
>>       mutex_unlock(&aux->mutex);
>> +    pm_runtime_mark_last_busy(dp_aux->dev);
>> +    pm_runtime_put_autosuspend(dp_aux->dev);
>>         return ret;
>>   }
>> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c 
>> b/drivers/gpu/drm/msm/dp/dp_display.c
>> index 76f1395..2c5706a 100644
>> --- a/drivers/gpu/drm/msm/dp/dp_display.c
>> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
>> @@ -309,6 +309,10 @@ static int dp_display_bind(struct device *dev, 
>> struct device *master,
>>           goto end;
>>       }
>>   +    pm_runtime_enable(dev);
>
> devm_pm_runtime_enable() removes need for a cleanup.
>
>> +    pm_runtime_set_autosuspend_delay(dev, 1000);
>> +    pm_runtime_use_autosuspend(dev);
>
> Why do you want to use autosuspend here?
>
>> +
>>       return 0;
>>   end:
>>       return rc;
>> @@ -320,9 +324,8 @@ static void dp_display_unbind(struct device *dev, 
>> struct device *master,
>>       struct dp_display_private *dp = dev_get_dp_display_private(dev);
>>       struct msm_drm_private *priv = dev_get_drvdata(master);
>>   -    /* disable all HPD interrupts */
>> -    if (dp->core_initialized)
>> -        dp_catalog_hpd_config_intr(dp->catalog, DP_DP_HPD_INT_MASK, 
>> false);
>> +    pm_runtime_dont_use_autosuspend(dev);
>> +    pm_runtime_disable(dev);
>>         kthread_stop(dp->ev_tsk);
>>   @@ -466,10 +469,12 @@ static void dp_display_host_init(struct 
>> dp_display_private *dp)
>>           dp->dp_display.connector_type, dp->core_initialized,
>>           dp->phy_initialized);
>>   -    dp_power_init(dp->power);
>> -    dp_ctrl_reset_irq_ctrl(dp->ctrl, true);
>> -    dp_aux_init(dp->aux);
>> -    dp->core_initialized = true;
>> +    if (!dp->core_initialized) {
>> +        dp_power_init(dp->power);
>> +        dp_ctrl_reset_irq_ctrl(dp->ctrl, true);
>> +        dp_aux_init(dp->aux);
>> +        dp->core_initialized = true;
>> +    }
>
> Is this relevant to PM runtime? I don't think so.
>
>>   }
>>     static void dp_display_host_deinit(struct dp_display_private *dp)
>> @@ -478,10 +483,12 @@ static void dp_display_host_deinit(struct 
>> dp_display_private *dp)
>>           dp->dp_display.connector_type, dp->core_initialized,
>>           dp->phy_initialized);
>>   -    dp_ctrl_reset_irq_ctrl(dp->ctrl, false);
>> -    dp_aux_deinit(dp->aux);
>> -    dp_power_deinit(dp->power);
>> -    dp->core_initialized = false;
>> +    if (dp->core_initialized) {
>> +        dp_ctrl_reset_irq_ctrl(dp->ctrl, false);
>> +        dp_aux_deinit(dp->aux);
>> +        dp_power_deinit(dp->power);
>> +        dp->core_initialized = false;
>> +    }
>>   }
>>     static int dp_display_usbpd_configure_cb(struct device *dev)
>> @@ -1304,6 +1311,39 @@ static int dp_display_remove(struct 
>> platform_device *pdev)
>>       dp_display_deinit_sub_modules(dp);
>>         platform_set_drvdata(pdev, NULL);
>> +    pm_runtime_put_sync_suspend(&pdev->dev);
>> +
>> +    return 0;
>> +}
>> +
>> +static int dp_pm_runtime_suspend(struct device *dev)
>> +{
>> +    struct platform_device *pdev = to_platform_device(dev);
>> +    struct msm_dp *dp_display = platform_get_drvdata(pdev);
>> +    struct dp_display_private *dp;
>> +
>> +    dp = container_of(dp_display, struct dp_display_private, 
>> dp_display);
>> +
>> +    dp_display_host_phy_exit(dp);
>> +    dp_catalog_ctrl_hpd_enable(dp->catalog);
>
> What? NO!
>
>> +    dp_display_host_deinit(dp);
>> +
>> +    return 0;
>> +}
>> +
>> +static int dp_pm_runtime_resume(struct device *dev)
>> +{
>> +    struct platform_device *pdev = to_platform_device(dev);
>> +    struct msm_dp *dp_display = platform_get_drvdata(pdev);
>> +    struct dp_display_private *dp;
>> +
>> +    dp = container_of(dp_display, struct dp_display_private, 
>> dp_display);
>> +
>> +    dp_display_host_init(dp);
>> +    if (dp_display->is_edp) {
>> +        dp_catalog_ctrl_hpd_enable(dp->catalog);
>> +        dp_display_host_phy_init(dp);
>> +    }
>>         return 0;
>>   }
>> @@ -1409,6 +1449,7 @@ static int dp_pm_suspend(struct device *dev)
>>   }
>>     static const struct dev_pm_ops dp_pm_ops = {
>> +    SET_RUNTIME_PM_OPS(dp_pm_runtime_suspend, dp_pm_runtime_resume, 
>> NULL)
>>       .suspend = dp_pm_suspend,
>>       .resume =  dp_pm_resume,
>
> With the runtime PM in place, can we change suspend/resume to use 
> pm_runtime_force_suspend() and pm_runtime_force_resume() ?

Let em try if i can move checking device connection status out of 
dp_pm_resume(). it handles external dp panel plugin/unplug during 
suspend cases.

>
>
>>   };
>> @@ -1493,10 +1534,6 @@ static int dp_display_get_next_bridge(struct 
>> msm_dp *dp)
>>       aux_bus = of_get_child_by_name(dev->of_node, "aux-bus");
>>         if (aux_bus && dp->is_edp) {
>> -        dp_display_host_init(dp_priv);
>> -        dp_catalog_ctrl_hpd_enable(dp_priv->catalog);
>> -        dp_display_host_phy_init(dp_priv);
>
> Are you going to populate the AUX bus (which can cause AUX bus access) 
> without waking up the device?

> devm_of_dp_aux_populate_ep_devices() ==>  will call 
> pm_runtiemget_sync() internally which will call pm_runtime_resume() to 
> wake dp driver
>> -
>>           /*
>>            * The code below assumes that the panel will finish probing
>>            * by the time devm_of_dp_aux_populate_ep_devices() returns.
>> @@ -1604,6 +1641,7 @@ void dp_bridge_atomic_enable(struct drm_bridge 
>> *drm_bridge,
>>           dp_hpd_plug_handle(dp_display, 0);
>
> Nearly the same question. Resume device before accessing registers.
>
>> mutex_lock(&dp_display->event_mutex);
>> +    pm_runtime_get_sync(&dp_display->pdev->dev);
>>         state = dp_display->hpd_state;
>>       if (state != ST_DISPLAY_OFF && state != ST_MAINLINK_READY) {
>> @@ -1684,6 +1722,8 @@ void dp_bridge_atomic_post_disable(struct 
>> drm_bridge *drm_bridge,
>>       }
>>         drm_dbg_dp(dp->drm_dev, "type=%d Done\n", dp->connector_type);
>> +
>> +    pm_runtime_put_sync(&dp_display->pdev->dev);
>>       mutex_unlock(&dp_display->event_mutex);
>>   }
>>   @@ -1723,6 +1763,8 @@ void dp_bridge_hpd_enable(struct drm_bridge 
>> *bridge)
>>       struct dp_display_private *dp = container_of(dp_display, struct 
>> dp_display_private, dp_display);
>>         mutex_lock(&dp->event_mutex);
>> +    pm_runtime_get_sync(&dp->pdev->dev);
>> +
>>       dp_catalog_ctrl_hpd_enable(dp->catalog);
>>         /* enable HDP interrupts */
>> @@ -1744,6 +1786,9 @@ void dp_bridge_hpd_disable(struct drm_bridge 
>> *bridge)
>>       dp_catalog_ctrl_hpd_disable(dp->catalog);
>>         dp_display->internal_hpd = false;
>> +
>> +    pm_runtime_mark_last_busy(&dp->pdev->dev);
>> +    pm_runtime_put_autosuspend(&dp->pdev->dev);
>>       mutex_unlock(&dp->event_mutex);
>>   }
>

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