drm/radeon/kms: fence cleanup + more reliable GPU lockup detection V4

This patch cleanup the fence code, it drops the timeout field of
fence as the time to complete each IB is unpredictable and shouldn't
be bound.

The fence cleanup lead to GPU lockup detection improvement, this
patch introduce a callback, allowing to do asic specific test for
lockup detection. In this patch the CP is use as a first indicator
of GPU lockup. If CP doesn't make progress during 1second we assume
we are facing a GPU lockup.

To avoid overhead of testing GPU lockup frequently due to fence
taking time to be signaled we query the lockup callback every
500msec. There is plenty code comment explaining the design & choise
inside the code.

This have been tested mostly on R3XX/R5XX hw, in normal running
destkop (compiz firefox, quake3 running) the lockup callback wasn't
call once (1 hour session). Also tested with forcing GPU lockup and
lockup was reported after the 1s CP activity timeout.

V2 switch to 500ms timeout so GPU lockup get call at least 2 times
   in less than 2sec.
V3 store last jiffies in fence struct so on ERESTART, EBUSY we keep
   track of how long we already wait for a given fence
V4 make sure we got up to date cp read pointer so we don't have
   false positive

Signed-off-by: Jerome Glisse <jglisse@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 86 insertions, 0 deletions

diff --git a/drivers/gpu/drm/radeon/r100.c b/drivers/gpu/drm/radeon/r100.c
index 3ae51ada1abf..845c8f3063fe 100644
--- a/drivers/gpu/drm/radeon/r100.c
+++ b/drivers/gpu/drm/radeon/r100.c
@@ -1777,6 +1777,92 @@ int r100_rb2d_reset(struct radeon_device *rdev)
         return -1;
 }
 
+void r100_gpu_lockup_update(struct r100_gpu_lockup *lockup, struct radeon_cp *cp)
+{
+        lockup->last_cp_rptr = cp->rptr;
+        lockup->last_jiffies = jiffies;
+}
+
+/**
+ * r100_gpu_cp_is_lockup() - check if CP is lockup by recording information
+ * @rdev:       radeon device structure
+ * @lockup:     r100_gpu_lockup structure holding CP lockup tracking informations
+ * @cp:         radeon_cp structure holding CP information
+ *
+ * We don't need to initialize the lockup tracking information as we will either
+ * have CP rptr to a different value of jiffies wrap around which will force
+ * initialization of the lockup tracking informations.
+ *
+ * A possible false positivie is if we get call after while and last_cp_rptr ==
+ * the current CP rptr, even if it's unlikely it might happen. To avoid this
+ * if the elapsed time since last call is bigger than 2 second than we return
+ * false and update the tracking information. Due to this the caller must call
+ * r100_gpu_cp_is_lockup several time in less than 2sec for lockup to be reported
+ * the fencing code should be cautious about that.
+ *
+ * Caller should write to the ring to force CP to do something so we don't get
+ * false positive when CP is just gived nothing to do.
+ *
+ **/
+bool r100_gpu_cp_is_lockup(struct radeon_device *rdev, struct r100_gpu_lockup *lockup, struct radeon_cp *cp)
+{
+        unsigned long cjiffies, elapsed;
+
+        cjiffies = jiffies;
+        if (!time_after(cjiffies, lockup->last_jiffies)) {
+                /* likely a wrap around */
+                lockup->last_cp_rptr = cp->rptr;
+                lockup->last_jiffies = jiffies;
+                return false;
+        }
+        if (cp->rptr != lockup->last_cp_rptr) {
+                /* CP is still working no lockup */
+                lockup->last_cp_rptr = cp->rptr;
+                lockup->last_jiffies = jiffies;
+                return false;
+        }
+        elapsed = jiffies_to_msecs(cjiffies - lockup->last_jiffies);
+        if (elapsed >= 3000) {
+                /* very likely the improbable case where current
+                 * rptr is equal to last recorded, a while ago, rptr
+                 * this is more likely a false positive update tracking
+                 * information which should force us to be recall at
+                 * latter point
+                 */
+                lockup->last_cp_rptr = cp->rptr;
+                lockup->last_jiffies = jiffies;
+                return false;
+        }
+        if (elapsed >= 1000) {
+                dev_err(rdev->dev, "GPU lockup CP stall for more than %lumsec\n", elapsed);
+                return true;
+        }
+        /* give a chance to the GPU ... */
+        return false;
+}
+
+bool r100_gpu_is_lockup(struct radeon_device *rdev)
+{
+        u32 rbbm_status;
+        int r;
+
+        rbbm_status = RREG32(R_000E40_RBBM_STATUS);
+        if (!G_000E40_GUI_ACTIVE(rbbm_status)) {
+                r100_gpu_lockup_update(&rdev->config.r100.lockup, &rdev->cp);
+                return false;
+        }
+        /* force CP activities */
+        r = radeon_ring_lock(rdev, 2);
+        if (!r) {
+                /* PACKET2 NOP */
+                radeon_ring_write(rdev, 0x80000000);
+                radeon_ring_write(rdev, 0x80000000);
+                radeon_ring_unlock_commit(rdev);
+        }
+        rdev->cp.rptr = RREG32(RADEON_CP_RB_RPTR);
+        return r100_gpu_cp_is_lockup(rdev, &rdev->config.r100.lockup, &rdev->cp);
+}
+
 int r100_gpu_reset(struct radeon_device *rdev)
 {
         uint32_t status;