Re: [PATCH v4 3/6] drm/i915/guc: refactor doorbell management code

[Yu Dai <yu.dai@intel.com>]

On 04/07/2016 10:21 AM, Dave Gordon wrote:
> During a hibernate/resume cycle, the driver, the GuC, and the doorbell
> hardware can end up in inconsistent states. This patch refactors the
> driver's handling and tracking of doorbells, in preparation for a later
> one which will resolve the issue.
>
> Signed-off-by: Dave Gordon <david.s.gordon@intel.com>
> ---
>   drivers/gpu/drm/i915/i915_guc_submission.c | 88 ++++++++++++++++++------------
>   1 file changed, 53 insertions(+), 35 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_guc_submission.c b/drivers/gpu/drm/i915/i915_guc_submission.c
> index 2171759..2fc69f1 100644
> --- a/drivers/gpu/drm/i915/i915_guc_submission.c
> +++ b/drivers/gpu/drm/i915/i915_guc_submission.c
> @@ -175,8 +175,48 @@ static int host2guc_sample_forcewake(struct intel_guc *guc,
>    * client object which contains the page being used for the doorbell
>    */
>   
> +static int guc_update_doorbell_id(struct i915_guc_client *client,
> +				  struct guc_doorbell_info *doorbell,
> +				  u16 new_id)
> +{
> +	struct sg_table *sg = client->guc->ctx_pool_obj->pages;
> +	void *doorbell_bitmap = client->guc->doorbell_bitmap;
> +	struct guc_context_desc desc;
> +	size_t len;
> +
> +	if (client->doorbell_id != GUC_INVALID_DOORBELL_ID &&
> +	    test_bit(client->doorbell_id, doorbell_bitmap)) {
> +		/* Deactivate the old doorbell */
> +		doorbell->db_status = GUC_DOORBELL_DISABLED;
> +		(void)host2guc_release_doorbell(client->guc, client);
> +		clear_bit(client->doorbell_id, doorbell_bitmap);
> +	}
> +
> +	/* Update the GuC's idea of the doorbell ID */
> +	len = sg_pcopy_to_buffer(sg->sgl, sg->nents, &desc, sizeof(desc),
> +			     sizeof(desc) * client->ctx_index);
> +	if (len != sizeof(desc))
> +		return -EFAULT;
> +	desc.db_id = new_id;
> +	len = sg_pcopy_from_buffer(sg->sgl, sg->nents, &desc, sizeof(desc),
> +			     sizeof(desc) * client->ctx_index);
> +	if (len != sizeof(desc))
> +		return -EFAULT;
> +

We may cache the vmap of context pool for its life cycle to avoid these 
copies. That is why a generic vmap helper function is really nice to have.

Alex
> +	client->doorbell_id = new_id;
> +	if (new_id == GUC_INVALID_DOORBELL_ID)
> +		return 0;
> +
> +	/* Activate the new doorbell */
> +	set_bit(client->doorbell_id, doorbell_bitmap);
> +	doorbell->db_status = GUC_DOORBELL_ENABLED;
> +	doorbell->cookie = 0;
> +	return host2guc_allocate_doorbell(client->guc, client);
> +}
> +
>   static void guc_init_doorbell(struct intel_guc *guc,
> -			      struct i915_guc_client *client)
> +			      struct i915_guc_client *client,
> +			      uint16_t db_id)
>   {
>   	struct guc_doorbell_info *doorbell;
>   	void *base;
> @@ -184,8 +224,7 @@ static void guc_init_doorbell(struct intel_guc *guc,
>   	base = kmap_atomic(i915_gem_object_get_page(client->client_obj, 0));
>   	doorbell = base + client->doorbell_offset;
>   
> -	doorbell->db_status = 1;
> -	doorbell->cookie = 0;
> +	guc_update_doorbell_id(client, doorbell, db_id);
>   
>   	kunmap_atomic(base);
>   }
> @@ -193,27 +232,16 @@ static void guc_init_doorbell(struct intel_guc *guc,
>   static void guc_disable_doorbell(struct intel_guc *guc,
>   				 struct i915_guc_client *client)
>   {
> -	struct drm_i915_private *dev_priv = guc_to_i915(guc);
>   	struct guc_doorbell_info *doorbell;
>   	void *base;
> -	i915_reg_t drbreg = GEN8_DRBREGL(client->doorbell_id);
> -	int value;
>   
>   	base = kmap_atomic(i915_gem_object_get_page(client->client_obj, 0));
>   	doorbell = base + client->doorbell_offset;
>   
> -	doorbell->db_status = 0;
> +	guc_update_doorbell_id(client, doorbell, GUC_INVALID_DOORBELL_ID);
>   
>   	kunmap_atomic(base);
>   
> -	I915_WRITE(drbreg, I915_READ(drbreg) & ~GEN8_DRB_VALID);
> -
> -	value = I915_READ(drbreg);
> -	WARN_ON((value & GEN8_DRB_VALID) != 0);
> -
> -	I915_WRITE(GEN8_DRBREGU(client->doorbell_id), 0);
> -	I915_WRITE(drbreg, 0);
> -
>   	/* XXX: wait for any interrupts */
>   	/* XXX: wait for workqueue to drain */
>   }
> @@ -260,7 +288,7 @@ static uint16_t assign_doorbell(struct intel_guc *guc, uint32_t priority)
>   	if (id == end)
>   		id = GUC_INVALID_DOORBELL_ID;
>   	else
> -		bitmap_set(guc->doorbell_bitmap, id, 1);
> +		set_bit(id, guc->doorbell_bitmap);
>   
>   	DRM_DEBUG_DRIVER("assigned %s priority doorbell id 0x%x\n",
>   			hi_pri ? "high" : "normal", id);
> @@ -268,11 +296,6 @@ static uint16_t assign_doorbell(struct intel_guc *guc, uint32_t priority)
>   	return id;
>   }
>   
> -static void release_doorbell(struct intel_guc *guc, uint16_t id)
> -{
> -	bitmap_clear(guc->doorbell_bitmap, id, 1);
> -}
> -
>   /*
>    * Initialise the process descriptor shared with the GuC firmware.
>    */
> @@ -667,15 +690,7 @@ static void guc_client_free(struct drm_device *dev,
>   	if (!client)
>   		return;
>   
> -	if (client->doorbell_id != GUC_INVALID_DOORBELL_ID) {
> -		/*
> -		 * First disable the doorbell, then tell the GuC we've
> -		 * finished with it, finally deallocate it in our bitmap
> -		 */
> -		guc_disable_doorbell(guc, client);
> -		host2guc_release_doorbell(guc, client);
> -		release_doorbell(guc, client->doorbell_id);
> -	}
> +	guc_disable_doorbell(guc, client);
>   
>   	/*
>   	 * XXX: wait for any outstanding submissions before freeing memory.
> @@ -712,6 +727,7 @@ static struct i915_guc_client *guc_client_alloc(struct drm_device *dev,
>   	struct drm_i915_private *dev_priv = dev->dev_private;
>   	struct intel_guc *guc = &dev_priv->guc;
>   	struct drm_i915_gem_object *obj;
> +	uint16_t db_id;
>   
>   	client = kzalloc(sizeof(*client), GFP_KERNEL);
>   	if (!client)
> @@ -750,22 +766,24 @@ static struct i915_guc_client *guc_client_alloc(struct drm_device *dev,
>   	else
>   		client->proc_desc_offset = (GUC_DB_SIZE / 2);
>   
> -	client->doorbell_id = assign_doorbell(guc, client->priority);
> -	if (client->doorbell_id == GUC_INVALID_DOORBELL_ID)
> +	db_id = assign_doorbell(guc, client->priority);
> +	if (db_id == GUC_INVALID_DOORBELL_ID)
>   		/* XXX: evict a doorbell instead */
>   		goto err;
>   
>   	guc_init_proc_desc(guc, client);
>   	guc_init_ctx_desc(guc, client);
> -	guc_init_doorbell(guc, client);
> +	guc_init_doorbell(guc, client, db_id);
>   
>   	/* XXX: Any cache flushes needed? General domain mgmt calls? */
>   
>   	if (host2guc_allocate_doorbell(guc, client))
>   		goto err;
>   
> -	DRM_DEBUG_DRIVER("new priority %u client %p: ctx_index %u db_id %u\n",
> -		priority, client, client->ctx_index, client->doorbell_id);
> +	DRM_DEBUG_DRIVER("new priority %u client %p: ctx_index %u\n",
> +		priority, client, client->ctx_index);
> +	DRM_DEBUG_DRIVER("doorbell id %u, cacheline offset 0x%x\n",
> +		client->doorbell_id, client->doorbell_offset);
>   
>   	return client;
>   

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