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Message-ID: <20231128145712.3f4d3f74@collabora.com>
Date: Tue, 28 Nov 2023 14:57:12 +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 13:45:10 +0100
AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
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@...labora.com>
> ---
> 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);
> 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);
>
> spinlock_t as_lock;
> unsigned long as_in_use_mask;
> diff --git a/drivers/gpu/drm/panfrost/panfrost_gpu.c b/drivers/gpu/drm/panfrost/panfrost_gpu.c
> index 7adc4441fa14..2bf645993ab4 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_gpu.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_gpu.c
> @@ -452,6 +452,13 @@ void panfrost_gpu_power_off(struct panfrost_device *pfdev)
> dev_err(pfdev->dev, "l2 power transition timeout");
> }
>
> +void panfrost_gpu_suspend_irq(struct panfrost_device *pfdev)
> +{
> + gpu_write(pfdev, GPU_INT_MASK, 0);
> + gpu_write(pfdev, GPU_INT_CLEAR, GPU_IRQ_MASK_ALL);
Shouldn't the synchronize_irq() guarantee that all monitored interrupts
are cleared before you return?
> + synchronize_irq(pfdev->gpu_irq);
> +}
> +
> int panfrost_gpu_init(struct panfrost_device *pfdev)
> {
> int err;
> diff --git a/drivers/gpu/drm/panfrost/panfrost_gpu.h b/drivers/gpu/drm/panfrost/panfrost_gpu.h
> index 876fdad9f721..d841b86504ea 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_gpu.h
> +++ b/drivers/gpu/drm/panfrost/panfrost_gpu.h
> @@ -15,6 +15,7 @@ u32 panfrost_gpu_get_latest_flush_id(struct panfrost_device *pfdev);
> int panfrost_gpu_soft_reset(struct panfrost_device *pfdev);
> void panfrost_gpu_power_on(struct panfrost_device *pfdev);
> void panfrost_gpu_power_off(struct panfrost_device *pfdev);
> +void panfrost_gpu_suspend_irq(struct panfrost_device *pfdev);
>
> void panfrost_cycle_counter_get(struct panfrost_device *pfdev);
> void panfrost_cycle_counter_put(struct panfrost_device *pfdev);
> diff --git a/drivers/gpu/drm/panfrost/panfrost_job.c b/drivers/gpu/drm/panfrost/panfrost_job.c
> index f9446e197428..e8de44cc56e2 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_job.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_job.c
> @@ -413,6 +413,14 @@ void panfrost_job_enable_interrupts(struct panfrost_device *pfdev)
> job_write(pfdev, JOB_INT_MASK, irq_mask);
> }
>
> +void panfrost_job_suspend_irq(struct panfrost_device *pfdev)
> +{
> + set_bit(PANFROST_COMP_BIT_JOB, pfdev->is_suspending);
> +
> + job_write(pfdev, JOB_INT_MASK, 0);
> + synchronize_irq(pfdev->js->irq);
> +}
> +
> static void panfrost_job_handle_err(struct panfrost_device *pfdev,
> struct panfrost_job *job,
> unsigned int js)
> @@ -792,9 +800,13 @@ static irqreturn_t panfrost_job_irq_handler_thread(int irq, void *data)
> struct panfrost_device *pfdev = data;
>
> panfrost_job_handle_irqs(pfdev);
> - job_write(pfdev, JOB_INT_MASK,
> - GENMASK(16 + NUM_JOB_SLOTS - 1, 16) |
> - GENMASK(NUM_JOB_SLOTS - 1, 0));
> +
> + /* Enable interrupts only if we're not about to get suspended */
> + if (!test_bit(PANFROST_COMP_BIT_JOB, pfdev->is_suspending))
The irq-line is requested with IRQF_SHARED, meaning the line might be
shared between all three GPU IRQs, but also with other devices. I think
if we want to be totally safe, we need to also check this is_suspending
field in the hard irq handlers before accessing the xxx_INT_yyy
registers.
> + job_write(pfdev, JOB_INT_MASK,
> + GENMASK(16 + NUM_JOB_SLOTS - 1, 16) |
> + GENMASK(NUM_JOB_SLOTS - 1, 0));
> +
> return IRQ_HANDLED;
> }
>
> diff --git a/drivers/gpu/drm/panfrost/panfrost_job.h b/drivers/gpu/drm/panfrost/panfrost_job.h
> index 17ff808dba07..ec581b97852b 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_job.h
> +++ b/drivers/gpu/drm/panfrost/panfrost_job.h
> @@ -47,6 +47,7 @@ int panfrost_job_get_slot(struct panfrost_job *job);
> int panfrost_job_push(struct panfrost_job *job);
> void panfrost_job_put(struct panfrost_job *job);
> void panfrost_job_enable_interrupts(struct panfrost_device *pfdev);
> +void panfrost_job_suspend_irq(struct panfrost_device *pfdev);
> int panfrost_job_is_idle(struct panfrost_device *pfdev);
>
> #endif
> diff --git a/drivers/gpu/drm/panfrost/panfrost_mmu.c b/drivers/gpu/drm/panfrost/panfrost_mmu.c
> index ac4296c1e54b..6ccf0a65b8fb 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_mmu.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_mmu.c
> @@ -744,9 +744,12 @@ static irqreturn_t panfrost_mmu_irq_handler_thread(int irq, void *data)
> status = mmu_read(pfdev, MMU_INT_RAWSTAT) & ~pfdev->as_faulty_mask;
> }
>
> - spin_lock(&pfdev->as_lock);
> - mmu_write(pfdev, MMU_INT_MASK, ~pfdev->as_faulty_mask);
> - spin_unlock(&pfdev->as_lock);
> + /* Enable interrupts only if we're not about to get suspended */
> + if (!test_bit(PANFROST_COMP_BIT_MMU, pfdev->is_suspending)) {
> + spin_lock(&pfdev->as_lock);
> + mmu_write(pfdev, MMU_INT_MASK, ~pfdev->as_faulty_mask);
> + spin_unlock(&pfdev->as_lock);
> + }
>
> return IRQ_HANDLED;
> };
> @@ -777,3 +780,11 @@ void panfrost_mmu_fini(struct panfrost_device *pfdev)
> {
> mmu_write(pfdev, MMU_INT_MASK, 0);
> }
> +
> +void panfrost_mmu_suspend_irq(struct panfrost_device *pfdev)
> +{
> + set_bit(PANFROST_COMP_BIT_MMU, pfdev->is_suspending);
> +
> + mmu_write(pfdev, MMU_INT_MASK, 0);
> + synchronize_irq(pfdev->mmu_irq);
> +}
> diff --git a/drivers/gpu/drm/panfrost/panfrost_mmu.h b/drivers/gpu/drm/panfrost/panfrost_mmu.h
> index cc2a0d307feb..022a9a74a114 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_mmu.h
> +++ b/drivers/gpu/drm/panfrost/panfrost_mmu.h
> @@ -14,6 +14,7 @@ void panfrost_mmu_unmap(struct panfrost_gem_mapping *mapping);
> int panfrost_mmu_init(struct panfrost_device *pfdev);
> void panfrost_mmu_fini(struct panfrost_device *pfdev);
> void panfrost_mmu_reset(struct panfrost_device *pfdev);
> +void panfrost_mmu_suspend_irq(struct panfrost_device *pfdev);
>
> u32 panfrost_mmu_as_get(struct panfrost_device *pfdev, struct panfrost_mmu *mmu);
> void panfrost_mmu_as_put(struct panfrost_device *pfdev, struct panfrost_mmu *mmu);
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