From b4bc35a780c6502fae2853eead0253ccd69e8945 Mon Sep 17 00:00:00 2001
From: Boris Brezillon <boris.brezillon@collabora.com>
Date: Wed, 30 Jun 2021 08:27:45 +0200
Subject: drm/panfrost: Make sure job interrupts are masked before resetting
Git-commit: 1d0cab5461d73c3b8d592e5324fcb05e63cf25ef
Patch-mainline: v5.15-rc1
References: jsc#PED-1166 jsc#PED-1168 jsc#PED-1170 jsc#PED-1218 jsc#PED-1220 jsc#PED-1222 jsc#PED-1223 jsc#PED-1225

This is not yet needed because we let active jobs be killed during by
the reset and we don't really bother making sure they can be restarted.
But once we start adding soft-stop support, controlling when we deal
with the remaining interrrupts and making sure those are handled before
the reset is issued gets tricky if we keep job interrupts active.

Let's prepare for that and mask+flush job IRQs before issuing a reset.

v4:
* Add a comment explaining why we WARN_ON(!job) in the irq handler
* Keep taking the job_lock when evicting stalled jobs

v3:
* New patch

Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210630062751.2832545-11-boris.brezillon@collabora.com
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
 drivers/gpu/drm/panfrost/panfrost_job.c | 27 ++++++++++++++++++++-----
 1 file changed, 22 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/panfrost/panfrost_job.c b/drivers/gpu/drm/panfrost/panfrost_job.c
index 59c23c91e47c..11ff33841caf 100644
--- a/drivers/gpu/drm/panfrost/panfrost_job.c
+++ b/drivers/gpu/drm/panfrost/panfrost_job.c
@@ -34,6 +34,7 @@ struct panfrost_queue_state {
 struct panfrost_job_slot {
 	struct panfrost_queue_state queue[NUM_JOB_SLOTS];
 	spinlock_t job_lock;
+	int irq;
 };
 
 static struct panfrost_job *
@@ -389,6 +390,15 @@ static void panfrost_reset(struct panfrost_device *pfdev,
 	if (bad)
 		drm_sched_increase_karma(bad);
 
+	/* Mask job interrupts and synchronize to make sure we won't be
+	 * interrupted during our reset.
+	 */
+	job_write(pfdev, JOB_INT_MASK, 0);
+	synchronize_irq(pfdev->js->irq);
+
+	/* Schedulers are stopped and interrupts are masked+flushed, we don't
+	 * need to protect the 'evict unfinished jobs' lock with the job_lock.
+	 */
 	spin_lock(&pfdev->js->job_lock);
 	for (i = 0; i < NUM_JOB_SLOTS; i++) {
 		if (pfdev->jobs[i]) {
@@ -486,7 +496,14 @@ static void panfrost_job_handle_irq(struct panfrost_device *pfdev, u32 status)
 			struct panfrost_job *job;
 
 			job = pfdev->jobs[j];
-			/* Only NULL if job timeout occurred */
+			/* The only reason this job could be NULL is if the
+			 * job IRQ handler is called just after the
+			 * in-flight job eviction in the reset path, and
+			 * this shouldn't happen because the job IRQ has
+			 * been masked and synchronized when this eviction
+			 * happens.
+			 */
+			WARN_ON(!job);
 			if (job) {
 				pfdev->jobs[j] = NULL;
 
@@ -546,7 +563,7 @@ static void panfrost_reset_work(struct work_struct *work)
 int panfrost_job_init(struct panfrost_device *pfdev)
 {
 	struct panfrost_job_slot *js;
-	int ret, j, irq;
+	int ret, j;
 
 	INIT_WORK(&pfdev->reset.work, panfrost_reset_work);
 
@@ -556,11 +573,11 @@ int panfrost_job_init(struct panfrost_device *pfdev)
 
 	spin_lock_init(&js->job_lock);
 
-	irq = platform_get_irq_byname(to_platform_device(pfdev->dev), "job");
-	if (irq <= 0)
+	js->irq = platform_get_irq_byname(to_platform_device(pfdev->dev), "job");
+	if (js->irq <= 0)
 		return -ENODEV;
 
-	ret = devm_request_threaded_irq(pfdev->dev, irq,
+	ret = devm_request_threaded_irq(pfdev->dev, js->irq,
 					panfrost_job_irq_handler,
 					panfrost_job_irq_handler_thread,
 					IRQF_SHARED, KBUILD_MODNAME "-job",
-- 
2.38.1