RE: [PATCH v2 2/4] drm/panfrost: Drop redundant optional clock checks in runtime PM

[Biju Das]

> -----Original Message-----
> From: dri-devel <dri-devel-bounces@xxxxxxxxxxxxxxxxxxxxx> On Behalf Of Adrián Larumbe
> Sent: 20 March 2026 21:20
> To: biju.das.au <biju.das.au@xxxxxxxxx>
> Cc: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>; Rob Herring <robh@xxxxxxxxxx>; Steven Price
> <steven.price@xxxxxxx>; Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>; Maxime Ripard
> <mripard@xxxxxxxxxx>; Thomas Zimmermann <tzimmermann@xxxxxxx>; David Airlie <airlied@xxxxxxxxx>;
> Simona Vetter <simona@xxxxxxxx>; Biju Das <biju.das.jz@xxxxxxxxxxxxxx>; dri-
> devel@xxxxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Geert Uytterhoeven
> <geert+renesas@xxxxxxxxx>; Prabhakar Mahadev Lad <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>; linux-
> renesas-soc@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH v2 2/4] drm/panfrost: Drop redundant optional clock checks in runtime PM
> 
> Hi Biju,
> 
> On 20.03.2026 16:41, Biju wrote:
> > From: Biju Das <biju.das.jz@xxxxxxxxxxxxxx>
> >
> > The clk_enable() and clk_disable() APIs already handle NULL clock
> > pointers gracefully — clk_enable() returns 0 and clk_disable() returns
> > immediately when passed a NULL or optional clock. The explicit if
> > (pfdev->bus_clock) guards around these calls in the runtime
> > suspend/resume paths are therefore unnecessary. Remove them to simplify the code.
> >
> > Reviewed-by: Steven Price <steven.price@xxxxxxx>
> > Signed-off-by: Biju Das <biju.das.jz@xxxxxxxxxxxxxx>
> > ---
> > v1->v2:
> >  * Collected tag
> > ---
> >  drivers/gpu/drm/panfrost/panfrost_device.c | 12 ++++--------
> >  1 file changed, 4 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/panfrost/panfrost_device.c
> > b/drivers/gpu/drm/panfrost/panfrost_device.c
> > index dedc13e56631..01e702a0b2f0 100644
> > --- a/drivers/gpu/drm/panfrost/panfrost_device.c
> > +++ b/drivers/gpu/drm/panfrost/panfrost_device.c
> > @@ -429,11 +429,9 @@ static int panfrost_device_runtime_resume(struct device *dev)
> >  		if (ret)
> >  			goto err_clk;
> >
> > -		if (pfdev->bus_clock) {
> > -			ret = clk_enable(pfdev->bus_clock);
> > -			if (ret)
> > -				goto err_bus_clk;
> > -		}
> > +		ret = clk_enable(pfdev->bus_clock);
> > +		if (ret)
> > +			goto err_bus_clk;
> >  	}
> 
> It seems clk_prepare_enable() can also deal with NULL clock device pointers gracefully, so maybe you
> could also do away with pointer checks in panfrost_clk_init?

This is the only check and no need to print rate for optional clk. That is the reason I have not
touched this.

	if (pfdev->bus_clock) {
		rate = clk_get_rate(pfdev->bus_clock);
		dev_info(pfdev->base.dev, "bus_clock rate = %lu\n", rate);

		err = clk_prepare_enable(pfdev->bus_clock);
		if (err)
			goto disable_clock;
	}

Cheers,
Biju
> 
> Other than that,
> 
> Reviewed-by: Adrián Larumbe <adrian.larumbe@xxxxxxxxxxxxx>
> 
> >  	panfrost_device_reset(pfdev, true);
> > @@ -464,9 +462,7 @@ static int panfrost_device_runtime_suspend(struct device *dev)
> >  	panfrost_gpu_power_off(pfdev);
> >
> >  	if (pfdev->comp->pm_features & BIT(GPU_PM_RT)) {
> > -		if (pfdev->bus_clock)
> > -			clk_disable(pfdev->bus_clock);
> > -
> > +		clk_disable(pfdev->bus_clock);
> >  		clk_disable(pfdev->clock);
> >  		reset_control_assert(pfdev->rstc);
> >  	}
> > --
> > 2.43.0
> 
> 
> Adrian Larumbe