drm/i915: Handle log buffer flush interrupt event from GuC

GuC ukernel sends an interrupt to Host to flush the log buffer
and expects Host to correspondingly update the read pointer
information in the state structure, once it has consumed the
log buffer contents by copying them to a file or buffer.
Even if Host couldn't copy the contents, it can still update the
read pointer so that logging state is not disturbed on GuC side.

v2:
- Use a dedicated workqueue for handling flush interrupt. (Tvrtko)
- Reduce the overall log buffer copying time by skipping the copy of
  crash buffer area for regular cases and copying only the state
  structure data in first page.

v3:
 - Create a vmalloc mapping of log buffer. (Chris)
 - Cover the flush acknowledgment under rpm get & put.(Chris)
 - Revert the change of skipping the copy of crash dump area, as
   not really needed, will be covered by subsequent patch.

v4:
 - Destroy the wq under the same condition in which it was created,
   pass dev_piv pointer instead of dev to newly added GuC function,
   add more comments & rename variable for clarity. (Tvrtko)

v5:
- Allocate & destroy the dedicated wq, for handling flush interrupt,
  from the setup/teardown routines of GuC logging. (Chris)
- Validate the log buffer size value retrieved from state structure
  and do some minor cleanup. (Tvrtko)
- Fix error/warnings reported by checkpatch. (Tvrtko)
- Rebase.

v6:
 - Remove the interrupts_enabled check from guc_capture_logs_work, need
   to process that last work item also, queued just before disabling the
   interrupt as log buffer flush interrupt handling is a bit different
   case where GuC is actually expecting an ACK from host, which should be
   provided to keep the logging going.
   Sync against the work will be done by caller disabling the interrupt.
 - Don't sample the log buffer size value from state structure, directly
   use the expected value to move the pointer & do the copy and that cannot
   go wrong (out of bounds) as Driver only allocated the log buffer and the
   relay buffers. Driver should refrain from interpreting the log packet,
   as much possible and let Userspace parser detect the anomaly. (Chris)

v7:
- Use switch statement instead of 'if else' for retrieving the GuC log
  buffer size. (Tvrtko)
- Refactored the log buffer copying function and shortended the name of
  couple of variables for better readability. (Tvrtko)

v8:
- Make the dedicated wq as a high priority one to further reduce the
  turnaround time of handing log buffer flush event from GuC.

Signed-off-by: Sagar Arun Kamble <sagar.a.kamble@intel.com>
Signed-off-by: Akash Goel <akash.goel@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

1 files changed, 27 insertions, 1 deletions

diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index b37959fdfb0e..253c22109c3f 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -1669,7 +1669,33 @@ static void gen6_rps_irq_handler(struct drm_i915_private *dev_priv, u32 pm_iir)
 static void gen9_guc_irq_handler(struct drm_i915_private *dev_priv, u32 gt_iir)
 {
 	if (gt_iir & GEN9_GUC_TO_HOST_INT_EVENT) {
-		/* TODO: Handle events for which GuC interrupted host */
+		/* Sample the log buffer flush related bits & clear them out now
+		 * itself from the message identity register to minimize the
+		 * probability of losing a flush interrupt, when there are back
+		 * to back flush interrupts.
+		 * There can be a new flush interrupt, for different log buffer
+		 * type (like for ISR), whilst Host is handling one (for DPC).
+		 * Since same bit is used in message register for ISR & DPC, it
+		 * could happen that GuC sets the bit for 2nd interrupt but Host
+		 * clears out the bit on handling the 1st interrupt.
+		 */
+		u32 msg, flush;
+
+		msg = I915_READ(SOFT_SCRATCH(15));
+		flush = msg & (GUC2HOST_MSG_CRASH_DUMP_POSTED |
+			       GUC2HOST_MSG_FLUSH_LOG_BUFFER);
+		if (flush) {
+			/* Clear the message bits that are handled */
+			I915_WRITE(SOFT_SCRATCH(15), msg & ~flush);
+
+			/* Handle flush interrupt in bottom half */
+			queue_work(dev_priv->guc.log.flush_wq,
+				   &dev_priv->guc.log.flush_work);
+		} else {
+			/* Not clearing of unhandled event bits won't result in
+			 * re-triggering of the interrupt.
+			 */
+		}
 	}
 }