[Intel-gfx] [PATCH 1/2] drm/i915/guc: Simplify code by keeping kmap of guc_client object

Daniel Vetter daniel at ffwll.ch
Wed Feb 17 16:04:57 UTC 2016

On Tue, Feb 16, 2016 at 08:47:07AM -0800, Yu Dai wrote:
> On 02/15/2016 07:23 AM, Dave Gordon wrote:
> >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.
> >
> >There's still one k(un)map_atomic() pair, in guc_add_workqueue_item().
> >Maybe we could get rid of that one too? So instead of kmapping only the
> >first page of the client, we could vmap() all three pages and so not
> >need to kmap_atomic() the WQ pages on the fly.
> >
> >There's a handy vmap_obj() function we might use, except it's currently
> >static ...
> >
> >
> Yes, there is a vmap_obj we can use but it is static. Actually two,
> vmap_batch() in i915_cmd_parser.c and vmap_obj() in intel_ringbuffer.c.
> Maybe it is a good idea to make it global, so GuC can use it too.

There should be a vmap function somewhere in the dma-buf code too iirc.
Daniel Vetter
Software Engineer, Intel Corporation

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