Re: [PATCH v4 3/6] media: iris: add iris4 specific H265 line buffer calculation

[Joonhoe Kim <26rote@gmail.com>]

On Thu, 01 Oct 2026 15:32:20 +0000, sashiko-bot@kernel.org wrote:
> > +		dpb_obp = size_dpb_opb(frame_height, lcu_size) * num_vpp_pipes;
[...]
> > +	return ((ALIGN(dpb_obp, DMA_ALIGNMENT) + ALIGN(se_left_lb, DMA_ALIGNMENT) +
> > +		ALIGN(vsp_left_lb, DMA_ALIGNMENT)) * num_vpp_pipes) +
[...]
> Does this code multiply dpb_obp by num_vpp_pipes twice?
[...]
> Is this double multiplication intentional, or should one of the
> multipliers be removed to prevent over-allocating the line buffer?

Some data on this from a Lenovo Y700 Gen 5 (TB323FU, Kaanapali), with
this patch on v7.3 and out-of-tree Kaanapali support. Hardware decodes
were compared bit for bit with software decoding:

                             HEVC Main10      HEVC Main
                             1080p   2160p    1080p
  v4 3/6 as is               pass    pass     pass
  dpb_obp multiplied once    fail    fail     pass
  once, OPB lines doubled
  for 10-bit output          pass    pass     pass

The failures are "session error received 0x4000005: insufficient
resources" with no frames decoded.

With num_vpp_pipes = 2, the second multiplication doubles dpb_obp.
That is what 10-bit output needs. With one multiplication, Main10
passes once the size_dpb_opb() part is doubled for a 10-bit capture
format. 8-bit streams pass without that.

Is the second multiplication meant to cover 10-bit output? If not, I
can send the 10-bit sizing as a patch on top of this series.

Thanks,
Joonhoe Kim