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

[Rob Herring]

On Fri, Aug 23, 2019 at 5:54 AM Robin Murphy <robin.murphy at arm.com> wrote:
>
> 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?

Leftover debugging to force issues. It should be 50.

Rob