On Tue, 28 Nov 2023 13:45:10 +0100
AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxx>
wrote:
> To make sure that we don't unintentionally perform any unclocked and/or
> unpowered R/W operation on GPU registers, before turning off clocks and
> regulators we must make sure that no GPU, JOB or MMU ISR execution is
> pending: doing that required to add a mechanism to synchronize the
> interrupts on suspend.
>
> Add functions panfrost_{gpu,job,mmu}_suspend_irq() which will perform
> interrupts masking and ISR execution synchronization, and then call
> those in the panfrost_device_runtime_suspend() handler in the exact
> sequence of job (may require mmu!) -> mmu -> gpu.
>
> As a side note, JOB and MMU suspend_irq functions needed some special
> treatment: as their interrupt handlers will unmask interrupts, it was
> necessary to add a bitmap for "is_suspending" which is used to address
> the possible corner case of unintentional IRQ unmasking because of ISR
> execution after a call to synchronize_irq().
>
> Of course, unmasking the interrupts is being done as part of the reset
> happening during runtime_resume(): since we're anyway resuming all of
> GPU, JOB, MMU, the only additional action is to zero out the newly
> introduced `is_suspending` bitmap directly in the resume handler, as
> to avoid adding panfrost_{job,mmu}_resume_irq() function just for
> clearing own bits, especially because it currently makes way more sense
> to just zero out the bitmap.
>
> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/panfrost/panfrost_device.c | 4 ++++
> drivers/gpu/drm/panfrost/panfrost_device.h | 7 +++++++
> drivers/gpu/drm/panfrost/panfrost_gpu.c | 7 +++++++
> drivers/gpu/drm/panfrost/panfrost_gpu.h | 1 +
> drivers/gpu/drm/panfrost/panfrost_job.c | 18 +++++++++++++++---
> drivers/gpu/drm/panfrost/panfrost_job.h | 1 +
> drivers/gpu/drm/panfrost/panfrost_mmu.c | 17 ++++++++++++++---
> drivers/gpu/drm/panfrost/panfrost_mmu.h | 1 +
> 8 files changed, 50 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/panfrost/panfrost_device.c b/drivers/gpu/drm/panfrost/panfrost_device.c
> index c90ad5ee34e7..ed34aa55a7da 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_device.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_device.c
> @@ -407,6 +407,7 @@ static int panfrost_device_runtime_resume(struct device *dev)
> {
> struct panfrost_device *pfdev = dev_get_drvdata(dev);
>
> + bitmap_zero(pfdev->is_suspending, PANFROST_COMP_BIT_MAX);
I would let each sub-block clear their bit in the reset path, since
that's where the IRQs are effectively unmasked.
> 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.
