Re: [PATCH 06/19] drm/i915: Handle log buffer flush interrupt event from GuC

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 19/08/16 09:43, akash.goel@intel.com wrote:
> From: Sagar Arun Kamble <sagar.a.kamble@intel.com>
>
> 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)
>
> Signed-off-by: Sagar Arun Kamble <sagar.a.kamble@intel.com>
> Signed-off-by: Akash Goel <akash.goel@intel.com>
> ---
>   drivers/gpu/drm/i915/i915_guc_submission.c | 189 +++++++++++++++++++++++++++++
>   drivers/gpu/drm/i915/i915_irq.c            |  28 ++++-
>   drivers/gpu/drm/i915/intel_guc.h           |   4 +
>   3 files changed, 220 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_guc_submission.c b/drivers/gpu/drm/i915/i915_guc_submission.c
> index b062da6..80e8725 100644
> --- a/drivers/gpu/drm/i915/i915_guc_submission.c
> +++ b/drivers/gpu/drm/i915/i915_guc_submission.c
> @@ -172,6 +172,15 @@ static int host2guc_sample_forcewake(struct intel_guc *guc,
>   	return host2guc_action(guc, data, ARRAY_SIZE(data));
>   }
>
> +static int host2guc_logbuffer_flush_complete(struct intel_guc *guc)
> +{
> +	u32 data[1];
> +
> +	data[0] = HOST2GUC_ACTION_LOG_BUFFER_FILE_FLUSH_COMPLETE;
> +
> +	return host2guc_action(guc, data, 1);
> +}
> +
>   /*
>    * Initialise, update, or clear doorbell data shared with the GuC
>    *
> @@ -828,6 +837,166 @@ err:
>   	return NULL;
>   }
>
> +static void guc_move_to_next_buf(struct intel_guc *guc)
> +{
> +}
> +
> +static void *guc_get_write_buffer(struct intel_guc *guc)
> +{
> +	return NULL;
> +}
> +
> +static unsigned int guc_get_log_buffer_size(enum guc_log_buffer_type type)
> +{
> +	switch (type) {
> +	case GUC_ISR_LOG_BUFFER:
> +		return (GUC_LOG_ISR_PAGES + 1) * PAGE_SIZE;
> +	case GUC_DPC_LOG_BUFFER:
> +		return (GUC_LOG_DPC_PAGES + 1) * PAGE_SIZE;
> +	case GUC_CRASH_DUMP_LOG_BUFFER:
> +		return (GUC_LOG_CRASH_PAGES + 1) * PAGE_SIZE;
> +	default:
> +		MISSING_CASE(type);
> +	}
> +
> +	return 0;
> +}
> +
> +static void guc_read_update_log_buffer(struct intel_guc *guc)
> +{
> +	struct guc_log_buffer_state *log_buf_state, *log_buf_snapshot_state;
> +	struct guc_log_buffer_state log_buf_state_local;
> +	unsigned int buffer_size, write_offset;
> +	enum guc_log_buffer_type type;
> +	void *src_data, *dst_data;
> +
> +	if (WARN_ON(!guc->log.buf_addr))
> +		return;
> +
> +	/* Get the pointer to shared GuC log buffer */
> +	log_buf_state = src_data = guc->log.buf_addr;
> +
> +	/* Get the pointer to local buffer to store the logs */
> +	log_buf_snapshot_state = dst_data = guc_get_write_buffer(guc);
> +
> +	/* Actual logs are present from the 2nd page */
> +	src_data += PAGE_SIZE;
> +	dst_data += PAGE_SIZE;
> +
> +	for (type = GUC_ISR_LOG_BUFFER; type < GUC_MAX_LOG_BUFFER; type++) {
> +		/* Make a copy of the state structure, inside GuC log buffer
> +		 * (which is uncached mapped), on the stack to avoid reading
> +		 * from it multiple times.
> +		 */
> +		memcpy(&log_buf_state_local, log_buf_state,
> +		       sizeof(struct guc_log_buffer_state));
> +		buffer_size = guc_get_log_buffer_size(type);
> +		write_offset = log_buf_state_local.sampled_write_ptr;
> +
> +		/* Update the state of shared log buffer */
> +		log_buf_state->read_ptr = write_offset;
> +		log_buf_state->flush_to_file = 0;
> +		log_buf_state++;
> +
> +		if (unlikely(!log_buf_snapshot_state))
> +			continue;
> +
> +		/* First copy the state structure in snapshot buffer */
> +		memcpy(log_buf_snapshot_state, &log_buf_state_local,
> +		       sizeof(struct guc_log_buffer_state));
> +
> +		/* The write pointer could have been updated by GuC firmware,
> +		 * after sending the flush interrupt to Host, for consistency
> +		 * set write pointer value to same value of sampled_write_ptr
> +		 * in the snapshot buffer.
> +		 */
> +		log_buf_snapshot_state->write_ptr = write_offset;
> +		log_buf_snapshot_state++;
> +
> +		/* Now copy the actual logs. */
> +		memcpy(dst_data, src_data, buffer_size);
> +
> +		src_data += buffer_size;
> +		dst_data += buffer_size;
> +
> +		/* FIXME: invalidate/flush for log buffer needed */
> +	}
> +
> +	if (log_buf_snapshot_state)
> +		guc_move_to_next_buf(guc);
> +}
> +
> +static void guc_capture_logs_work(struct work_struct *work)
> +{
> +	struct drm_i915_private *dev_priv =
> +		container_of(work, struct drm_i915_private, guc.log.flush_work);
> +
> +	i915_guc_capture_logs(dev_priv);
> +}
> +
> +static void guc_log_cleanup(struct intel_guc *guc)
> +{
> +	struct drm_i915_private *dev_priv = guc_to_i915(guc);
> +
> +	lockdep_assert_held(&dev_priv->drm.struct_mutex);
> +
> +	if (i915.guc_log_level < 0)
> +		return;
> +
> +	/* First disable the flush interrupt */
> +	gen9_disable_guc_interrupts(dev_priv);
> +
> +	if (guc->log.flush_wq)
> +		destroy_workqueue(guc->log.flush_wq);
> +
> +	guc->log.flush_wq = NULL;
> +
> +	if (guc->log.buf_addr)
> +		i915_gem_object_unpin_map(guc->log.vma->obj);
> +
> +	guc->log.buf_addr = NULL;
> +}
> +
> +static int guc_create_log_extras(struct intel_guc *guc)
> +{
> +	struct drm_i915_private *dev_priv = guc_to_i915(guc);
> +	void *vaddr;
> +	int ret;
> +
> +	lockdep_assert_held(&dev_priv->drm.struct_mutex);
> +
> +	/* Nothing to do */
> +	if (i915.guc_log_level < 0)
> +		return 0;
> +
> +	if (!guc->log.buf_addr) {
> +		/* Create a vmalloc mapping of log buffer pages */
> +		vaddr = i915_gem_object_pin_map(guc->log.vma->obj, I915_MAP_WB);
> +		if (IS_ERR(vaddr)) {
> +			ret = PTR_ERR(vaddr);
> +			DRM_ERROR("Couldn't map log buffer pages %d\n", ret);
> +			return ret;
> +		}
> +
> +		guc->log.buf_addr = vaddr;
> +	}
> +
> +	if (!guc->log.flush_wq) {
> +		INIT_WORK(&guc->log.flush_work, guc_capture_logs_work);
> +
> +		/* Need a dedicated wq to process log buffer flush interrupts
> +		 * from GuC without much delay so as to avoid any loss of logs.
> +		 */
> +		guc->log.flush_wq = alloc_ordered_workqueue("i915-guc_log", 0);
> +		if (guc->log.flush_wq == NULL) {
> +			DRM_ERROR("Couldn't allocate the wq for GuC logging\n");
> +			return -ENOMEM;
> +		}
> +	}
> +
> +	return 0;
> +}
> +
>   static void guc_create_log(struct intel_guc *guc)
>   {
>   	struct i915_vma *vma;
> @@ -853,6 +1022,13 @@ static void guc_create_log(struct intel_guc *guc)
>   		}
>
>   		guc->log.vma = vma;
> +
> +		if (guc_create_log_extras(guc)) {
> +			guc_log_cleanup(guc);
> +			i915_vma_unpin_and_release(&guc->log.vma);
> +			i915.guc_log_level = -1;
> +			return;
> +		}
>   	}
>
>   	/* each allocated unit is a page */
> @@ -1034,6 +1210,7 @@ void i915_guc_submission_fini(struct drm_i915_private *dev_priv)
>   	struct intel_guc *guc = &dev_priv->guc;
>
>   	i915_vma_unpin_and_release(&guc->ads_vma);
> +	guc_log_cleanup(guc);
>   	i915_vma_unpin_and_release(&guc->log.vma);
>
>   	if (guc->ctx_pool_vma)
> @@ -1095,3 +1272,15 @@ int intel_guc_resume(struct drm_device *dev)
>
>   	return host2guc_action(guc, data, ARRAY_SIZE(data));
>   }
> +
> +void i915_guc_capture_logs(struct drm_i915_private *dev_priv)
> +{
> +	guc_read_update_log_buffer(&dev_priv->guc);
> +
> +	/* Generally device is expected to be active only at this
> +	 * time, so get/put should be really quick.
> +	 */
> +	intel_runtime_pm_get(dev_priv);
> +	host2guc_logbuffer_flush_complete(&dev_priv->guc);
> +	intel_runtime_pm_put(dev_priv);
> +}
> diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
> index fc1fe72..19c0078 100644
> --- a/drivers/gpu/drm/i915/i915_irq.c
> +++ b/drivers/gpu/drm/i915/i915_irq.c
> @@ -1662,7 +1662,33 @@ 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.
> +			 */
> +		}
>   	}
>   }
>
> diff --git a/drivers/gpu/drm/i915/intel_guc.h b/drivers/gpu/drm/i915/intel_guc.h
> index 1fc63fe..d053a18 100644
> --- a/drivers/gpu/drm/i915/intel_guc.h
> +++ b/drivers/gpu/drm/i915/intel_guc.h
> @@ -124,6 +124,9 @@ struct intel_guc_fw {
>   struct intel_guc_log {
>   	uint32_t flags;
>   	struct i915_vma *vma;
> +	void *buf_addr;
> +	struct workqueue_struct *flush_wq;
> +	struct work_struct flush_work;
>   };
>
>   struct intel_guc {
> @@ -167,5 +170,6 @@ int i915_guc_submission_enable(struct drm_i915_private *dev_priv);
>   int i915_guc_wq_check_space(struct drm_i915_gem_request *rq);
>   void i915_guc_submission_disable(struct drm_i915_private *dev_priv);
>   void i915_guc_submission_fini(struct drm_i915_private *dev_priv);
> +void i915_guc_capture_logs(struct drm_i915_private *dev_priv);
>
>   #endif
>

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Regards,

Tvrtko
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