Re: [PATCH v2] drm/panfrost: Ignore core_mask for poweroff and sync interrupts

[AngeloGioacchino Del Regno]

Il 23/11/23 12:57, Krzysztof Kozlowski ha scritto:
> On 23/11/2023 12:50, AngeloGioacchino Del Regno wrote:
> > Some SoCs may be equipped with a GPU containing two core groups
> > and this is exactly the case of Samsung's Exynos 5422 featuring
> > an ARM Mali-T628 MP6 GPU: the support for this GPU in Panfrost
> > is partial, as this driver currently supports using only one
> > core group and that's reflected on all parts of it, including
> > the power on (and power off, previously to this patch) function.
> >
> > The issue with this is that even though executing the soft reset
> > operation should power off all cores unconditionally, on at least
> > one platform we're seeing a crash that seems to be happening due
> > to an interrupt firing which may be because we are calling power
> > transition only on the first core group, leaving the second one
> > unchanged, or because ISR execution was pending before entering
> > the panfrost_gpu_power_off() function and executed after powering
> > off the GPU cores, or all of the above.
> >
> > Finally, solve this by introducing a new panfrost_gpu_suspend_irq()
> > helper function and changing the panfrost_device_suspend() flow to
> >   1. Mask and clear all interrupts: we don't need nor want any, as
> >      for power_off() we are polling PWRTRANS, but we anyway don't
> >      want GPU IRQs to fire while it is suspended/powered off;
> >   2. Call synchronize_irq() after that to make sure that any pending
> >      ISR is executed before powering off the GPU Shaders/Tilers/L2
> >      hence avoiding unpowered registers R/W; and
> >   3. Ignore the core_mask and ask the GPU to poweroff both core groups
> >
> > Of course it was also necessary to add a `irq` variable to `struct
> > panfrost_device` as we need to get that in panfrost_gpu_power_off()
> > for calling synchronize_irq() on it.
> >
> > Fixes: 22aa1a209018 ("drm/panfrost: Really power off GPU cores in panfrost_gpu_power_off()")
> > [Regression detected on Odroid HC1, Exynos5422, Mali-T628 MP6]
> > Reported-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>
> > Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxx>
> > ---
> >
> > Changes in v2:
> >   - Fixed the commit hash of "Really power off [...]"
> >   - Actually based on a clean next-20231121
> >   - Renamed "irq" to "gpu_irq" as per Boris' suggestion
> >   - Moved the IRQ mask/clear/sync to a helper function and added
> >     a call to that in panfrost_device.c instead of doing that in
> >     panfrost_gpu_power_off().
> >
> > NOTE: I didn't split 1+2 from 3 as suggested by Boris, and I'm sending
> > this one without waiting for feedback on my reasons for that which I
> > explained as a reply to v1 because the former couldn't be applied to
> > linux-next, and I want to unblock Krzysztof ASAP to get this tested.
>
> This does not compile.

I really have to take a break. My brain starts failing, as I can see.

Sorry.