Re: [PATCH 2/2] drm/panfrost: add devfreq regulator support

[ClÃment PÃron]

Hi Steven,

On Mon, 13 Apr 2020 at 18:35, ClÃment PÃron <peron.clem@xxxxxxxxx> wrote:
>
> Hi Steven,
>
> On Mon, 13 Apr 2020 at 17:55, Steven Price <steven.price@xxxxxxx> wrote:
> >
> > On 13/04/2020 15:31, ClÃment PÃron wrote:
> > > Hi,
> > >
> > > On Mon, 13 Apr 2020 at 16:18, ClÃment PÃron <peron.clem@xxxxxxxxx> wrote:
> > >>
> > >> Hi Steven,
> > >>
> > >> On Mon, 13 Apr 2020 at 15:18, Steven Price <steven.price@xxxxxxx> wrote:
> > >>>
> > >>> On 11/04/2020 21:06, ClÃment PÃron wrote:
> > >>>> OPP table can defined both frequency and voltage.
> > >>>>
> > >>>> Register the mali regulator if it exist.
> > >>>>
> > >>>> Signed-off-by: ClÃment PÃron <peron.clem@xxxxxxxxx>
> > >>>> ---
> > >>>>    drivers/gpu/drm/panfrost/panfrost_devfreq.c | 34 ++++++++++++++++++---
> > >>>>    drivers/gpu/drm/panfrost/panfrost_device.h  |  1 +
> > >>>>    2 files changed, 31 insertions(+), 4 deletions(-)
> > >>>>
> > >>>> diff --git a/drivers/gpu/drm/panfrost/panfrost_devfreq.c b/drivers/gpu/drm/panfrost/panfrost_devfreq.c
> > >>>> index 62541f4edd81..2dc8e2355358 100644
> > >>>> --- a/drivers/gpu/drm/panfrost/panfrost_devfreq.c
> > >>>> +++ b/drivers/gpu/drm/panfrost/panfrost_devfreq.c
> > >>>> @@ -78,12 +78,26 @@ int panfrost_devfreq_init(struct panfrost_device *pfdev)
> > >>>>        struct device *dev = &pfdev->pdev->dev;
> > >>>>        struct devfreq *devfreq;
> > >>>>        struct thermal_cooling_device *cooling;
> > >>>> +     const char *mali = "mali";
> > >>>> +     struct opp_table *opp_table = NULL;
> > >>>> +
> > >>>> +     /* Regulator is optional */
> > >>>> +     opp_table = dev_pm_opp_set_regulators(dev, &mali, 1);
> > >>>
> > >>> This looks like it applies before 3e1399bccf51 ("drm/panfrost: Add
> > >>> support for multiple regulators") which is currently in drm-misc-next
> > >>> (and linux-next). You want something more like:
> > >>
> > >> Thanks for you review, indeed I didn't see that multiple regulators
> > >> support has been added.
> > >> Will update in v2.
> > >>
> > >>>
> > >>>       opp_table = dev_pm_opp_set_regulators(dev,
> > >>>                                             pfdev->comp->supply_names,
> > >>>                                             pfdev->comp->num_supplies);
> > >>>
> > >>> Otherwise a platform with multiple regulators won't work correctly.
> > >>>
> > >>> Also running on my firefly (RK3288) board I get the following warning:
> > >>>
> > >>>      debugfs: Directory 'ffa30000.gpu-mali' with parent 'vdd_gpu' already
> > >>> present!

I try to reproduce but it can't
regulator is mount at :
./regulator/vdd-gpu
whereas OPP is mount :
./opp/soc-1800000.gpu/opp:756000000/supply-0/

I see that firefly as 2 regulators with the same name :
vdd_gpu from syr828
(https://github.com/mopplayer/Firefly-RK3288-Kernel-With-Mali764/blob/master/arch/arm/boot/dts/firefly-rk3288.dts#L453)
vdd_gpu from rk808_dcdc2_reg
(https://github.com/mopplayer/Firefly-RK3288-Kernel-With-Mali764/blob/master/arch/arm/boot/dts/firefly-rk3288.dts#L841)

So i think the issue is from the firefly device-tree.

Regards,
Clement

> > >>>
> > >>> This is due to the regulator debugfs entries getting created twice (once
> > >>> in panfrost_regulator_init() and once here).
> > >>
> > >> Is it a warning that should be consider as an error? Look's more an info no?
> > >> What should be the correct behavior if a device want to register two
> > >> times the same regulator?
> > >
> > > Or we can change the name from vdd_XXX to opp_vdd_XXX ?
> > > https://elixir.bootlin.com/linux/latest/source/drivers/opp/debugfs.c#L45
> >
> > Yes, I'm not sure that it's actually a problem in practice. And it may
> > well be correct to change this in the generic code rather than try to
> > work around it in Panfrost. But we shouldn't spam the user with warnings
> > as that makes real issues harder to see.
> >
> > Your suggestion to change the name seems reasonable to me, but I don't
> > fully understand the opp code, so we'd need some review from the OPP
> > maintainers. Hopefully Viresh, Nishanth or Stephen can provide some insight.
>
> Agree, I will send a v2 with the rename and see if OPP Maintainers agree.
>
> Regards,
> Clement
>
> >
> > Steve