linux-kernel - Re: [PATCH v2 3/3] drm/panfrost: Synchronize and disable interrupts before powering off

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Date:   Tue, 28 Nov 2023 16:58:40 +0100
From:   Boris Brezillon <boris.brezillon@...labora.com>
To:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
Cc:     robh@...nel.org, steven.price@....com,
        maarten.lankhorst@...ux.intel.com, mripard@...nel.org,
        tzimmermann@...e.de, airlied@...il.com, daniel@...ll.ch,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        kernel@...labora.com, m.szyprowski@...sung.com,
        krzysztof.kozlowski@...aro.org
Subject: Re: [PATCH v2 3/3] drm/panfrost: Synchronize and disable interrupts
 before powering off

On Tue, 28 Nov 2023 16:42:25 +0100
AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
wrote:

> >>  
> >>>>    	panfrost_device_reset(pfdev);
> >>>>    	panfrost_devfreq_resume(pfdev);
> >>>>    
> >>>> @@ -421,6 +422,9 @@ static int panfrost_device_runtime_suspend(struct device *dev)
> >>>>    		return -EBUSY;
> >>>>    
> >>>>    	panfrost_devfreq_suspend(pfdev);
> >>>> +	panfrost_job_suspend_irq(pfdev);
> >>>> +	panfrost_mmu_suspend_irq(pfdev);
> >>>> +	panfrost_gpu_suspend_irq(pfdev);
> >>>>    	panfrost_gpu_power_off(pfdev);
> >>>>    
> >>>>    	return 0;
> >>>> diff --git a/drivers/gpu/drm/panfrost/panfrost_device.h b/drivers/gpu/drm/panfrost/panfrost_device.h
> >>>> index 54a8aad54259..29f89f2d3679 100644
> >>>> --- a/drivers/gpu/drm/panfrost/panfrost_device.h
> >>>> +++ b/drivers/gpu/drm/panfrost/panfrost_device.h
> >>>> @@ -25,6 +25,12 @@ struct panfrost_perfcnt;
> >>>>    #define NUM_JOB_SLOTS 3
> >>>>    #define MAX_PM_DOMAINS 5
> >>>>    
> >>>> +enum panfrost_drv_comp_bits {
> >>>> +	PANFROST_COMP_BIT_MMU,
> >>>> +	PANFROST_COMP_BIT_JOB,
> >>>> +	PANFROST_COMP_BIT_MAX
> >>>> +};
> >>>> +
> >>>>    /**
> >>>>     * enum panfrost_gpu_pm - Supported kernel power management features
> >>>>     * @GPU_PM_CLK_DIS:  Allow disabling clocks during system suspend
> >>>> @@ -109,6 +115,7 @@ struct panfrost_device {
> >>>>    
> >>>>    	struct panfrost_features features;
> >>>>    	const struct panfrost_compatible *comp;
> >>>> +	DECLARE_BITMAP(is_suspending, PANFROST_COMP_BIT_MAX);  
> >>>
> >>> nit: Maybe s/is_suspending/suspended_irqs/, given the state remains
> >>> until the device is resumed.  
> >>
> >> If we keep the `is_suspending` name, we can use this one more generically in
> >> case we ever need to, what do you think?  
> > 
> > I'm lost. Why would we want to reserve a name for something we don't
> > know about? My comment was mostly relating to the fact this bitmap
> > doesn't reflect the is_suspending state, but rather is_suspended,
> > because it remains set until the device is resumed. And we actually want
> > it to reflect the is_suspended state, so we can catch interrupts that
> > are not for us without reading regs in the hard irq handler, when the
> > GPU is suspended.  
> 
> `is_suspended` (fun story: that's the first name I gave it) looks good to me,
> the doubt I raised was about calling it `suspended_irqs` instead, as I would
> prefer to keep names "more generic", but that's just personal preference at
> this point anyway.

Ah, sure, is_suspended is fine.