Re: [Intel-gfx] [PATCH 04/10] drm/i915/guc: Add a second client, to be used for preemption

Thu, 05 Oct 2017 06:59:56 -0700

On Thu, 05 Oct 2017 11:13:43 +0200, Michał Winiarski <michal.winiar...@intel.com> wrote: 


From: Dave Gordon <david.s.gor...@intel.com>

This second client is created with priority KMD_HIGH, and marked
as preemptive. This will allow us to request preemption using GuC actions. 

Cc: Chris Wilson <ch...@chris-wilson.co.uk>
Cc: Jeff Mcgee <jeff.mc...@intel.com>
Cc: Michal Wajdeczko <michal.wajdec...@intel.com>
Cc: Oscar Mateo <oscar.ma...@intel.com>
Signed-off-by: Dave Gordon <david.s.gor...@intel.com>
Signed-off-by: Michał Winiarski <michal.winiar...@intel.com>
---
 drivers/gpu/drm/i915/i915_debugfs.c        |  4 ++++
drivers/gpu/drm/i915/i915_guc_submission.c | 32 ++++++++++++++++++++++++++---- 
 drivers/gpu/drm/i915/intel_uc.h            |  1 +
 3 files changed, 33 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c 
index b4a6ac60e7c6..1a963c13cab8 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -2488,6 +2488,10 @@ static int i915_guc_info(struct seq_file *m, void *data) 
        seq_printf(m, "\nGuC execbuf client @ %p:\n", guc->execbuf_client);
        i915_guc_client_info(m, dev_priv, guc->execbuf_client);
+       if (guc->preempt_client) {
+               seq_printf(m, "\nGuC preempt client\n");


Maybe to match output from 'execbuf' there should be "@ %p:"


+               i915_guc_client_info(m, dev_priv, guc->preempt_client);
+       }
        i915_guc_log_info(m, dev_priv);
diff --git a/drivers/gpu/drm/i915/i915_guc_submission.c b/drivers/gpu/drm/i915/i915_guc_submission.c 
index 374501a67274..e8052e86426d 100644
--- a/drivers/gpu/drm/i915/i915_guc_submission.c
+++ b/drivers/gpu/drm/i915/i915_guc_submission.c
@@ -331,6 +331,8 @@ static void guc_stage_desc_init(struct intel_guc *guc, 
        memset(desc, 0, sizeof(*desc));
desc->attribute = GUC_STAGE_DESC_ATTR_ACTIVE | GUC_STAGE_DESC_ATTR_KERNEL; 
+       if (client->priority <= GUC_CLIENT_PRIORITY_HIGH)
+               desc->attribute |= GUC_STAGE_DESC_ATTR_PREEMPT;
        desc->stage_id = client->stage_id;
        desc->priority = client->priority;
        desc->db_id = client->doorbell_id;
@@ -1154,7 +1156,7 @@ int i915_guc_submission_enable(struct drm_i915_private *dev_priv) 
                     sizeof(struct guc_wq_item) *
                     I915_NUM_ENGINES > GUC_WQ_SIZE);
-       if (!client) {


Make sure to remove unnecessary earlier assignment:
        client = guc->execbuf_client;


+       if (!guc->execbuf_client) {
                client = guc_client_alloc(dev_priv,
                                          INTEL_INFO(dev_priv)->ring_mask,
                                          GUC_CLIENT_PRIORITY_KMD_NORMAL,
@@ -1167,15 +1169,29 @@ int i915_guc_submission_enable(struct drm_i915_private *dev_priv) 
                guc->execbuf_client = client;
        }
+       if (!guc->preempt_client) {
+               client = guc_client_alloc(dev_priv,
+                                         INTEL_INFO(dev_priv)->ring_mask,
+                                         GUC_CLIENT_PRIORITY_KMD_HIGH,
+                                         dev_priv->preempt_context);
+               if (IS_ERR(client)) {
+                       DRM_ERROR("Failed to create GuC client for 
preemption!\n");
+                       err = PTR_ERR(client);
+                       goto err_free_clients;
+               }
+
+               guc->preempt_client = client;
+       }
+


If we allow clients to be already created here, then maybe we should
move their creation into separate helper inline to clearly mark that.
Then we will have simpler error handling sequence ;)


        err = intel_guc_sample_forcewake(guc);
        if (err)
-               goto err_execbuf_client;
+               goto err_free_clients;
        guc_reset_wq(client);
        err = guc_init_doorbell_hw(guc);
        if (err)
-               goto err_execbuf_client;
+               goto err_free_clients;
        /* Take over from manual control of ELSP (execlists) */
        guc_interrupts_capture(dev_priv);
@@ -1187,7 +1203,11 @@ int i915_guc_submission_enable(struct drm_i915_private *dev_priv) 
        return 0;
-err_execbuf_client:
+err_free_clients:
+       if (guc->preempt_client) {
+               guc_client_free(guc->preempt_client);
+               guc->preempt_client = NULL;
+       }
        guc_client_free(guc->execbuf_client);
        guc->execbuf_client = NULL;
        return err;
@@ -1202,6 +1222,10 @@ void i915_guc_submission_disable(struct drm_i915_private *dev_priv) 
        /* Revert back to manual ELSP submission */
        intel_engines_reset_default_submission(dev_priv);
+       if (guc->preempt_client) {
+               guc_client_free(guc->preempt_client);
+               guc->preempt_client = NULL;
+       }
        guc_client_free(guc->execbuf_client);
        guc->execbuf_client = NULL;
 }
diff --git a/drivers/gpu/drm/i915/intel_uc.h b/drivers/gpu/drm/i915/intel_uc.h 
index 10e8f0ed02e4..c6c6f8513bbf 100644
--- a/drivers/gpu/drm/i915/intel_uc.h
+++ b/drivers/gpu/drm/i915/intel_uc.h
@@ -107,6 +107,7 @@ struct intel_guc {
        struct ida stage_ids;
        struct i915_guc_client *execbuf_client;
+       struct i915_guc_client *preempt_client;
        DECLARE_BITMAP(doorbell_bitmap, GUC_NUM_DOORBELLS);
        uint32_t db_cacheline;          /* Cyclic counter mod pagesize  */

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