[Intel-gfx] [PATCH 1/2] drm/i915/guc: Simplify code by keeping kmap of guc_client object
david.s.gordon at intel.com
Mon Feb 15 14:39:31 UTC 2016
On 12/02/16 13:03, Tvrtko Ursulin wrote:
> On 11/02/16 23:09, yu.dai at intel.com wrote:
>> From: Alex Dai <yu.dai at intel.com>
>> GuC client object is always pinned during its life cycle. We cache
>> the kmap of its first page, which includes guc_process_desc and
>> doorbell. By doing so, we can simplify the code where we read from
>> this page to get where GuC is progressing on work queue; and the
>> code where driver program doorbell to send work queue item to GuC.
>> - /* Finally, update the cached copy of the GuC's WQ head */
>> - gc->wq_head = desc->head;
> Did you mean to remove the above?
I wondered that too at first, but the answer is "yes" -- see below.
>> + client->client_base = kmap(i915_gem_object_get_dirty_page(obj, 0));
> Was this another bug, that the page/object wasn't dirtied before?
It wouldn't have made any difference; the object is pinned in the GTT
forever, so it can't be swapped out or reclaimed.
>> - uint32_t wq_head;
> Hm ok I don't get why kmap caching means removing this as well?
'wq_head' was an optimisation so that we could check whether there was
known to be space in the workqueue without kmapping and reading the
process descriptor. Now that the client (which includes the process
descriptor) is permanently mapped, there's no advantage to caching the
head; we might just as well read the current value from 'desc->head'
> Btw I don't see patch 2/2 ?
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