Panfrost impossible to probe without opp table

[Clément Péron]

Hi,


On Fri, 31 May 2019 at 14:13, Neil Armstrong <narmstrong at baylibre.com> wrote:
>
> On 31/05/2019 14:09, Tomeu Vizoso wrote:
> > On Fri, 31 May 2019 at 14:03, Neil Armstrong <narmstrong at baylibre.com> wrote:
> >>
> >> Hi Tomeu,
> >>
> >> On 31/05/2019 13:59, Tomeu Vizoso wrote:
> >>> On Wed, 29 May 2019 at 23:29, Clément Péron <peron.clem at gmail.com> wrote:
> >>>>
> >>>> Hi,
> >>>>
> >>>> I have rebase my kernel on latest 5.2-rc2, and my panfrost driver is
> >>>> no more probing.
> >>>>
> >>>> The issue is coming from f3617b449d0bcf3b5d80a97f51498dcf7463cf7e
> >>>>     drm/panfrost: Select devfreq
> >>>>
> >>>>     Currently, there is some logic for the driver to work without devfreq.
> >>>>     However, the driver actually fails to probe if !CONFIG_PM_DEVFREQ.
> >>>>
> >>>>     Fix this by selecting devfreq, and drop the additional checks
> >>>>     for devfreq.
> >>>>
> >>>> It seems that with this commit the OPP table is now mandatory.
> >>>> is it intentional?
> >>>
> >>> Hi Clément,
> >>>
> >>> devfreq support is intentionally required. I got a H64 board which I'm
> >>> using to add T720 support to Panfrost.
> >>
> >> operating-points-v2 and clocks are optional, devfreq should be optional,
> >> this was the default behaviour of the first applied version.
> >
> > I'm concerned by the safety of running these GPUs all the time at
> > their maximum frequencies. Maybe not on Chromebooks and other consumer
> > devices, but the SBCs I have here have all very crappy heat
> > dissipation.
>
> Sure, it's logical to have devfreq running on these devices.
>
> >
> >> Amlogic dt does not have operating-points-v2, and devfreq won't be supported
> >> soon.
> >
> > What's the problem with coming up with the operating points?
>
> Because the bindings are optional :
> Optional properties:
>
> - clocks : Phandle to clock for the Mali Midgard device.
>
> - mali-supply : Phandle to regulator for the Mali device. Refer to
>   Documentation/devicetree/bindings/regulator/regulator.txt for details.
>
> - operating-points-v2 : Refer to Documentation/devicetree/bindings/opp/opp.txt
>   for details.
>
> Unless you change the bindings, it's mandated to be optional by the bindings.

I can propose a patch to fix this but what is the best solution?

Leave DEVFREQ config mandatory but allow to probe without opp_table?
Revert the commit?
Fix the documentation to have opp table mandatory?

Thanks,
Clément

>
> Neil
>
>
> >
> > Thanks,
> >
> > Tomeu
> >
> >> Neil
> >>
> >>>
> >>> Once I'm able to test the GPU properly along with frequency scaling, I
> >>> will ping you so you can retest and resubmit.
> >>>
> >>> Thanks,
> >>>
> >>> Tomeu
> >>>
> >>>> Actually
> >>>> [    3.046237] panfrost 1800000.gpu: clock rate = 432000000
> >>>> [    3.051593] panfrost 1800000.gpu: bus_clock rate = 100000000
> >>>> [    3.096012] panfrost 1800000.gpu: mali-t720 id 0x720 major 0x1
> >>>> minor 0x1 status 0x0
> >>>> [    3.103682] panfrost 1800000.gpu: features: 00000000,10309e40,
> >>>> issues: 00000000,21054400
> >>>> [    3.111789] panfrost 1800000.gpu: Features: L2:0x07110206
> >>>> Shader:0x00000000 Tiler:0x00000809 Mem:0x1 MMU:0x00002821 AS:0xf
> >>>> JS:0x7
> >>>> [    3.123435] panfrost 1800000.gpu: shader_present=0x3 l2_present=0x1
> >>>> [    3.130405] panfrost 1800000.gpu: Fatal error during devfreq init
> >>>>
> >>>> With commit reverted
> >>>> [    3.038236] panfrost 1800000.gpu: clock rate = 432000000
> >>>> [    3.043593] panfrost 1800000.gpu: bus_clock rate = 100000000
> >>>> [    3.087994] panfrost 1800000.gpu: mali-t720 id 0x720 major 0x1
> >>>> minor 0x1 status 0x0
> >>>> [    3.095658] panfrost 1800000.gpu: features: 00000000,10309e40,
> >>>> issues: 00000000,21054400
> >>>> [    3.103763] panfrost 1800000.gpu: Features: L2:0x07110206
> >>>> Shader:0x00000000 Tiler:0x00000809 Mem:0x1 MMU:0x00002821 AS:0xf
> >>>> JS:0x7
> >>>> [    3.115410] panfrost 1800000.gpu: shader_present=0x3 l2_present=0x1
> >>>> [    3.122798] [drm] Initialized panfrost 1.0.0 20180908 for
> >>>> 1800000.gpu on minor 0
> >>>>
> >>>>
> >>>> Thanks,
> >>>> Clément
> >>>>
> >>>> _______________________________________________
> >>>> linux-arm-kernel mailing list
> >>>> linux-arm-kernel at lists.infradead.org
> >>>> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
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> >>>
> >>
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>