[PATCH v2 2/8] drm/panfrost: Rework runtime PM initialization

[Robin Murphy]

On 23/08/2019 03:12, Rob Herring wrote:
> There's a few issues with the runtime PM initialization.
> 
> The documentation states pm_runtime_set_active() should be called before
> pm_runtime_enable(). The pm_runtime_put_autosuspend() could suspend the GPU
> before panfrost_perfcnt_init() is called which touches the h/w. The
> autosuspend delay keeps things from breaking. There's no need explicitly
> power off the GPU only to wake back up with pm_runtime_get_sync(). Just
> delaying pm_runtime_enable to the end of probe is sufficient.
> 
> Lets move all the runtime PM calls into the probe() function so they are
> all in one place and are done after all initialization.
> 
> Cc: Tomeu Vizoso <tomeu.vizoso at collabora.com>
> Cc: Steven Price <steven.price at arm.com>
> Cc: Alyssa Rosenzweig <alyssa.rosenzweig at collabora.com>
> Cc: David Airlie <airlied at linux.ie>
> Cc: Daniel Vetter <daniel at ffwll.ch>
> Signed-off-by: Rob Herring <robh at kernel.org>
> ---
> v2: new patch
> 
>   drivers/gpu/drm/panfrost/panfrost_device.c |  9 ---------
>   drivers/gpu/drm/panfrost/panfrost_drv.c    | 10 ++++++----
>   2 files changed, 6 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panfrost/panfrost_device.c b/drivers/gpu/drm/panfrost/panfrost_device.c
> index 4da71bb56c20..73805210834e 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_device.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_device.c
> @@ -5,7 +5,6 @@
>   #include <linux/clk.h>
>   #include <linux/reset.h>
>   #include <linux/platform_device.h>
> -#include <linux/pm_runtime.h>
>   #include <linux/regulator/consumer.h>
>   
>   #include "panfrost_device.h"
> @@ -166,14 +165,6 @@ int panfrost_device_init(struct panfrost_device *pfdev)
>   	if (err)
>   		goto err_out4;
>   
> -	/* runtime PM will wake us up later */
> -	panfrost_gpu_power_off(pfdev);
> -
> -	pm_runtime_set_active(pfdev->dev);
> -	pm_runtime_get_sync(pfdev->dev);
> -	pm_runtime_mark_last_busy(pfdev->dev);
> -	pm_runtime_put_autosuspend(pfdev->dev);
> -
>   	err = panfrost_perfcnt_init(pfdev);
>   	if (err)
>   		goto err_out5;
> diff --git a/drivers/gpu/drm/panfrost/panfrost_drv.c b/drivers/gpu/drm/panfrost/panfrost_drv.c
> index d74442d71048..f27e3d6aec12 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_drv.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_drv.c
> @@ -523,10 +523,6 @@ static int panfrost_probe(struct platform_device *pdev)
>   	mutex_init(&pfdev->shrinker_lock);
>   	INIT_LIST_HEAD(&pfdev->shrinker_list);
>   
> -	pm_runtime_use_autosuspend(pfdev->dev);
> -	pm_runtime_set_autosuspend_delay(pfdev->dev, 50); /* ~3 frames */
> -	pm_runtime_enable(pfdev->dev);
> -
>   	err = panfrost_device_init(pfdev);
>   	if (err) {
>   		if (err != -EPROBE_DEFER)
> @@ -541,6 +537,12 @@ static int panfrost_probe(struct platform_device *pdev)
>   		goto err_out1;
>   	}
>   
> +	pm_runtime_set_active(pfdev->dev);
> +	pm_runtime_use_autosuspend(pfdev->dev);
> +	pm_runtime_set_autosuspend_delay(pfdev->dev, 0); /* ~3 frames */

Hmm... different timeout, same comment - something seems amiss there, 
unless perhaps it's all within rounding error anyway?

Other than that, the overall change looks sensible to me.

Robin.

> +	pm_runtime_mark_last_busy(pfdev->dev);
> +	pm_runtime_enable(pfdev->dev);
> +
>   	/*
>   	 * Register the DRM device with the core and the connectors with
>   	 * sysfs
>