On 02/10/2016 09:30 AM, Tvrtko Ursulin wrote:
Hi,
On 10/02/16 00:05, yu.dai@xxxxxxxxx wrote:
> From: Alex Dai <yu.dai@xxxxxxxxx>
>
> The cached work queue header pointer is set to last byte of work
> queue buffer. It will make sure the whole work queue buffer is
> available after coming back from reset or init.
>
> Do not hold kmap_atomic mapping before going to sleep when work
> queue is full.
Could you please split this into two patches? They are two completely
separate issues and it is customary to do so.
For the kmap_atomic issue you can also reference
https://bugs.freedesktop.org/show_bug.cgi?id=93847 in the commit message.
Yes, will do.
> Signed-off-by: Alex Dai <yu.dai@xxxxxxxxx>
> ---
> drivers/gpu/drm/i915/i915_guc_submission.c | 10 +++++-----
> 1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_guc_submission.c b/drivers/gpu/drm/i915/i915_guc_submission.c
> index d7543ef..41f4a96 100644
> --- a/drivers/gpu/drm/i915/i915_guc_submission.c
> +++ b/drivers/gpu/drm/i915/i915_guc_submission.c
> @@ -486,11 +486,11 @@ int i915_guc_wq_check_space(struct i915_guc_client *gc)
> if (CIRC_SPACE(gc->wq_tail, gc->wq_head, gc->wq_size) >= size)
> return 0;
>
> - base = kmap_atomic(i915_gem_object_get_page(gc->client_obj, 0));
> - desc = base + gc->proc_desc_offset;
> -
> while (timeout_counter-- > 0) {
> + base = kmap_atomic(i915_gem_object_get_page(gc->client_obj, 0));
> + desc = base + gc->proc_desc_offset;
> gc->wq_head = desc->head;
> + kunmap_atomic(base);
>
> if (CIRC_SPACE(gc->wq_tail, gc->wq_head, gc->wq_size) >= size) {
> ret = 0;
> @@ -501,8 +501,6 @@ int i915_guc_wq_check_space(struct i915_guc_client *gc)
> usleep_range(1000, 2000);
> };
>
> - kunmap_atomic(base);
> -
> return ret;
> }
This part is OK to extinguish this fire. But in general you could also
consider caching the kmap in the client since it looks to me that object
is persistently pinned for its lifetime. So kmap_atomic just complicates
things.
Yes this object must be pinned for its lifetime as it is used by GuC
internally too. I will think about a way to cache it.
> @@ -730,6 +728,8 @@ static struct i915_guc_client *guc_client_alloc(struct drm_device *dev,
> client->client_obj = obj;
> client->wq_offset = GUC_DB_SIZE;
> client->wq_size = GUC_WQ_SIZE;
> + client->wq_head = GUC_WQ_SIZE - 1;
> + client->wq_tail = 0;
>
> client->doorbell_offset = select_doorbell_cacheline(guc);
>
>
This one I can't really figure out without I suppose knowing more about
the code design. How come it was OK when it was zero (apart after reset)?
The value is otherwise only updated from the GuC shared page and a
driver does not appear to modify it. Perhaps just a better commit
message to explain things?
The way this kernel CIRC_xx works is it leaves one byte free and treat
head == tail case as empty. So, there won't be a problem if this head
happens to be 0. If it comes with some random number between [1,
sizeof(WQ item)], there will be a SW dead looping in driver.
And, I will split this patch into two ones.
Thanks,
Alex
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