[PATCH] drm/amdgpu: try again kiq access if not in IRQ(v3)

[Monk Liu]

sometimes GPU is switched to other VFs and won't swich
back soon, so the kiq reg access will not signal within
a short period, instead of busy waiting a long time(MAX_KEQ_REG_WAIT)
and returning TMO we can istead sleep 5ms and try again
later (non irq context)

And since the waiting in kiq_r/weg is busy wait, so MAX_KIQ_REG_WAIT
shouldn't set to a long time, set it to 10ms is more appropriate.

if gpu already in reset state, don't retry the KIQ reg access
otherwise it would always hang because KIQ was already die usually.

v2:
replace schedule() with msleep() for the wait

v3:
use while loop for the wait repeating
use macros for the sleep period
more description for it

Change-Id: I088243be6ccf722f6d80c3e70c62271d37edb40d
Signed-off-by: Monk Liu <Monk.Liu at amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_virt.c | 62 ++++++++++++++++++++++++++------
 1 file changed, 52 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_virt.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_virt.c
index b832651..43ce2e5 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_virt.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_virt.c
@@ -22,7 +22,9 @@
  */
 
 #include "amdgpu.h"
-#define MAX_KIQ_REG_WAIT	100000000 /* in usecs */
+#define MAX_KIQ_REG_WAIT	5000 /* in usecs, 5ms */
+#define MAX_KIQ_REG_BAILOUT_INTERVAL	5 /* in msecs, 5ms */
+#define MAX_KIQ_REG_TRY 20
 
 uint64_t amdgpu_csa_vaddr(struct amdgpu_device *adev)
 {
@@ -137,7 +139,7 @@ void amdgpu_virt_init_setting(struct amdgpu_device *adev)
 
 uint32_t amdgpu_virt_kiq_rreg(struct amdgpu_device *adev, uint32_t reg)
 {
-	signed long r;
+	signed long r, cnt = 0;
 	unsigned long flags;
 	uint32_t val, seq;
 	struct amdgpu_kiq *kiq = &adev->gfx.kiq;
@@ -153,18 +155,36 @@ uint32_t amdgpu_virt_kiq_rreg(struct amdgpu_device *adev, uint32_t reg)
 	spin_unlock_irqrestore(&kiq->ring_lock, flags);
 
 	r = amdgpu_fence_wait_polling(ring, seq, MAX_KIQ_REG_WAIT);
-	if (r < 1) {
-		DRM_ERROR("wait for kiq fence error: %ld\n", r);
-		return ~0;
+
+	/* don't wait anymore for gpu reset case because this way may
+	 * block gpu_recover() routine forever, e.g. this virt_kiq_rreg
+	 * is triggered in TTM and ttm_bo_lock_delayed_workqueue() will
+	 * never return if we keep waiting in virt_kiq_rreg, which cause
+	 * gpu_recover() hang there.
+	 *
+	 * also don't wait anymore for IRQ context
+	 * */
+	if (r < 1 && (adev->in_gpu_reset || in_interrupt()))
+		goto failed_kiq_read;
+
+	while (r < 1 && cnt++ < MAX_KIQ_REG_TRY) {
+		msleep(MAX_KIQ_REG_BAILOUT_INTERVAL);
+		r = amdgpu_fence_wait_polling(ring, seq, MAX_KIQ_REG_WAIT);
 	}
-	val = adev->wb.wb[adev->virt.reg_val_offs];
 
-	return val;
+	if (cnt > MAX_KIQ_REG_TRY)
+		goto failed_kiq_read;
+
+	return adev->wb.wb[adev->virt.reg_val_offs];
+
+failed_kiq_read:
+	pr_err("failed to read reg:%x\n", reg);
+	return ~0;
 }
 
 void amdgpu_virt_kiq_wreg(struct amdgpu_device *adev, uint32_t reg, uint32_t v)
 {
-	signed long r;
+	signed long r, cnt = 0;
 	unsigned long flags;
 	uint32_t seq;
 	struct amdgpu_kiq *kiq = &adev->gfx.kiq;
@@ -180,8 +200,30 @@ void amdgpu_virt_kiq_wreg(struct amdgpu_device *adev, uint32_t reg, uint32_t v)
 	spin_unlock_irqrestore(&kiq->ring_lock, flags);
 
 	r = amdgpu_fence_wait_polling(ring, seq, MAX_KIQ_REG_WAIT);
-	if (r < 1)
-		DRM_ERROR("wait for kiq fence error: %ld\n", r);
+
+	/* don't wait anymore for gpu reset case because this way may
+	 * block gpu_recover() routine forever, e.g. this virt_kiq_rreg
+	 * is triggered in TTM and ttm_bo_lock_delayed_workqueue() will
+	 * never return if we keep waiting in virt_kiq_rreg, which cause
+	 * gpu_recover() hang there.
+	 *
+	 * also don't wait anymore for IRQ context
+	 * */
+	if (r < 1 && (adev->in_gpu_reset || in_interrupt()))
+		goto failed_kiq_write;
+
+	while (r < 1 && cnt++ < MAX_KIQ_REG_TRY) {
+		msleep(MAX_KIQ_REG_BAILOUT_INTERVAL);
+		r = amdgpu_fence_wait_polling(ring, seq, MAX_KIQ_REG_WAIT);
+	}
+
+	if (cnt > MAX_KIQ_REG_TRY)
+		goto failed_kiq_write;
+
+	return;
+
+failed_kiq_write:
+	pr_err("failed to write reg:%x\n", reg);
 }
 
 /**
-- 
2.7.4