drm/panfrost: Synchronize and disable interrupts before powering off

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 requires 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 an `is_suspended` bitmap which is used to address the
possible corner case of unintentional IRQ unmasking because of ISR
execution after a call to synchronize_irq().

At resume, clear each is_suspended bit in the reset path of JOB/MMU
to allow unmasking the interrupts.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231204114215.54575-4-angelogioacchino.delregno@collabora.com

1 files changed, 16 insertions, 2 deletions

diff --git a/drivers/gpu/drm/panfrost/panfrost_gpu.c b/drivers/gpu/drm/panfrost/panfrost_gpu.c
index 7adc4441fa14..9063ce254642 100644
--- a/drivers/gpu/drm/panfrost/panfrost_gpu.c
+++ b/drivers/gpu/drm/panfrost/panfrost_gpu.c
@@ -22,9 +22,13 @@
 static irqreturn_t panfrost_gpu_irq_handler(int irq, void *data)
 {
 	struct panfrost_device *pfdev = data;
-	u32 state = gpu_read(pfdev, GPU_INT_STAT);
-	u32 fault_status = gpu_read(pfdev, GPU_FAULT_STATUS);
+	u32 fault_status, state;
 
+	if (test_bit(PANFROST_COMP_BIT_GPU, pfdev->is_suspended))
+		return IRQ_NONE;
+
+	fault_status = gpu_read(pfdev, GPU_FAULT_STATUS);
+	state = gpu_read(pfdev, GPU_INT_STAT);
 	if (!state)
 		return IRQ_NONE;
 
@@ -61,6 +65,8 @@ int panfrost_gpu_soft_reset(struct panfrost_device *pfdev)
 	gpu_write(pfdev, GPU_INT_MASK, 0);
 	gpu_write(pfdev, GPU_INT_CLEAR, GPU_IRQ_RESET_COMPLETED);
 
+	clear_bit(PANFROST_COMP_BIT_GPU, pfdev->is_suspended);
+
 	gpu_write(pfdev, GPU_CMD, GPU_CMD_SOFT_RESET);
 	ret = readl_relaxed_poll_timeout(pfdev->iomem + GPU_INT_RAWSTAT,
 		val, val & GPU_IRQ_RESET_COMPLETED, 10, 10000);
@@ -452,6 +458,14 @@ 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)
+{
+	set_bit(PANFROST_COMP_BIT_GPU, pfdev->is_suspended);
+
+	gpu_write(pfdev, GPU_INT_MASK, 0);
+	synchronize_irq(pfdev->gpu_irq);
+}
+
 int panfrost_gpu_init(struct panfrost_device *pfdev)
 {
 	int err;