Update: UVD status on loongson 3a platform

Chen Jie chenj at lemote.com
Thu Sep 5 07:14:32 PDT 2013

Hi all,

This thread is about

We recently find some interesting thing about UVD based playback on
loongson 3a plaform, and also find a way to fix the problem.

First, we find memcpy in [mesa]src/gallium/drivers/radeon/radeon_uvd.c
caused the problem:
* If memcpy is implemented though 16B or 8B load/store instructions,
it will normally caused video mosaic. When insert a memcmp after the
copying code in memcpy, it will report the src and dest are not equal.
* If memcpy use 1B load/store instructions only, the memcmp after the
copying code reports equal.

Then we find the following changeset fixs out problem:

diff --git a/src/gallium/drivers/radeon/radeon_uvd.c
index 2f98de2..f9599b6 100644
--- a/src/gallium/drivers/radeon/radeon_uvd.c
+++ b/src/gallium/drivers/radeon/radeon_uvd.c
@@ -162,7 +162,7 @@ static bool create_buffer(struct ruvd_decoder *dec,
   unsigned size)
  buffer->buf = dec->ws->buffer_create(dec->ws, size, 4096, false,
  if (!buffer->buf)
  return false;

The VRAM is mapped to an uncached area in out platform, so, my
question is what could go wrong while using  >4B load/store
instructions in UVD workflow? Any idea?

-- Regards,

Chen Jie

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