Re: [PATCH 02/10] drm/tidss: Use PM autosuspend

[Tomi Valkeinen]

On 01/11/2023 15:54, Laurent Pinchart wrote:
> Hi Tomi,
>
> Thank you for the patch.
>
> On Wed, Nov 01, 2023 at 11:17:39AM +0200, Tomi Valkeinen wrote:
> > Use runtime PM autosuspend feature, with 1s timeout, to avoid
> > unnecessary suspend-resume cycles when, e.g. the userspace temporarily
> > turns off the crtcs when configuring the outputs.
> >
> > Signed-off-by: Tomi Valkeinen <tomi.valkeinen@xxxxxxxxxxxxxxxx>
> > ---
> >   drivers/gpu/drm/tidss/tidss_drv.c | 8 +++++++-
> >   1 file changed, 7 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/tidss/tidss_drv.c b/drivers/gpu/drm/tidss/tidss_drv.c
> > index f403db11b846..64914331715a 100644
> > --- a/drivers/gpu/drm/tidss/tidss_drv.c
> > +++ b/drivers/gpu/drm/tidss/tidss_drv.c
> > @@ -43,7 +43,9 @@ void tidss_runtime_put(struct tidss_device *tidss)
> >   
> >   	dev_dbg(tidss->dev, "%s\n", __func__);
> >   
> > -	r = pm_runtime_put_sync(tidss->dev);
> > +	pm_runtime_mark_last_busy(tidss->dev);
> > +
> > +	r = pm_runtime_put_autosuspend(tidss->dev);
> >   	WARN_ON(r < 0);
> >   }
> >   
> > @@ -144,6 +146,9 @@ static int tidss_probe(struct platform_device *pdev)
> >   
> >   	pm_runtime_enable(dev);
> >   
> > +	pm_runtime_set_autosuspend_delay(dev, 1000);
> > +	pm_runtime_use_autosuspend(dev);
> > +
> >   #ifndef CONFIG_PM
> >   	/* If we don't have PM, we need to call resume manually */
> >   	dispc_runtime_resume(tidss->dispc);
>
> By the way, there's a way to handle this without any ifdef:
>
> 	dispc_runtime_resume(tidss->dispc);
>
> 	pm_runtime_set_active(dev);
> 	pm_runtime_get_noresume(dev);
> 	pm_runtime_enable(dev);
> 	pm_runtime_set_autosuspend_delay(dev, 1000);
> 	pm_runtime_use_autosuspend(dev);

I'm not sure I follow what you are trying to do here. The call to 
dispc_runtime_resume() would crash if we have PM, as the HW would not be 
enabled at that point. And even if it wouldn't, we don't want to call 
dispc_runtime_resume() in probe when we have PM.

> Then, in the error path,
>
> 	pm_runtime_dont_use_autosuspend(dev);
> 	pm_runtime_disable(dev);
> 	pm_runtime_put_noidle(dev);
>
> 	dispc_runtime_suspend(tidss->dispc);
>
> And in remove:
>
> 	pm_runtime_dont_use_autosuspend(dev);
> 	pm_runtime_disable(dev);
> 	if (!pm_runtime_status_suspended(dev))
> 		dispc_runtime_suspend(tidss->dispc);
> 	pm_runtime_set_suspended(dev);
>
> And yes, runtime PM is a horrible API.
>
> > @@ -215,6 +220,7 @@ static void tidss_remove(struct platform_device *pdev)
> >   	/* If we don't have PM, we need to call suspend manually */
> >   	dispc_runtime_suspend(tidss->dispc);
> >   #endif
> > +	pm_runtime_dont_use_autosuspend(dev);
>
> This also needs to be done in the probe error path.

Oops. Right, I'll add that.

 Tomi