Re: [PATCH 4/9] media: vsp1: Add support for missing 32-bit RGB formats

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Jacopo,

On Thu, Apr 04, 2019 at 07:39:05PM +0200, Jacopo Mondi wrote:
> HI Laurent,
>   if you help me out understanding the bit swapping procedure in VSP
> I would be more confident in saying I actually reviewed the series.

I'll try my best :-)

> On Thu, Mar 28, 2019 at 09:07:18AM +0200, Laurent Pinchart wrote:
> > Add support for the V4L2_PIX_FMT_BGRA32, V4L2_PIX_FMT_BGRX32,
> > V4L2_PIX_FMT_RGBA32 and V4L2_PIX_FMT_RGBX32 formats to the VSP driver.
> >
> > Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
> > ---
> >  drivers/media/platform/vsp1/vsp1_pipe.c | 14 ++++++++++++++
> >  1 file changed, 14 insertions(+)
> >
> > diff --git a/drivers/media/platform/vsp1/vsp1_pipe.c b/drivers/media/platform/vsp1/vsp1_pipe.c
> > index 54ff539ffea0..9f08d85e89d7 100644
> > --- a/drivers/media/platform/vsp1/vsp1_pipe.c
> > +++ b/drivers/media/platform/vsp1/vsp1_pipe.c
> > @@ -68,6 +68,20 @@ static const struct vsp1_format_info vsp1_video_formats[] = {
> >  	{ V4L2_PIX_FMT_XBGR32, MEDIA_BUS_FMT_ARGB8888_1X32,
> >  	  VI6_FMT_ARGB_8888, VI6_RPF_DSWAP_P_LLS | VI6_RPF_DSWAP_P_LWS,
> >  	  1, { 32, 0, 0 }, false, false, 1, 1, false },
> > +	{ V4L2_PIX_FMT_BGRA32, MEDIA_BUS_FMT_ARGB8888_1X32,
> > +	  VI6_FMT_RGBA_8888, VI6_RPF_DSWAP_P_LLS | VI6_RPF_DSWAP_P_LWS,
> > +	  1, { 32, 0, 0 }, false, false, 1, 1, true },
> > +	{ V4L2_PIX_FMT_BGRX32, MEDIA_BUS_FMT_ARGB8888_1X32,
> > +	  VI6_FMT_RGBA_8888, VI6_RPF_DSWAP_P_LLS | VI6_RPF_DSWAP_P_LWS,
> > +	  1, { 32, 0, 0 }, false, false, 1, 1, false },
> > +	{ V4L2_PIX_FMT_RGBA32, MEDIA_BUS_FMT_ARGB8888_1X32,
> > +	  VI6_FMT_RGBA_8888, VI6_RPF_DSWAP_P_LLS | VI6_RPF_DSWAP_P_LWS |
> > +	  VI6_RPF_DSWAP_P_WDS | VI6_RPF_DSWAP_P_BTS,
> > +	  1, { 32, 0, 0 }, false, false, 1, 1, true },
> > +	{ V4L2_PIX_FMT_RGBX32, MEDIA_BUS_FMT_ARGB8888_1X32,
> > +	  VI6_FMT_RGBA_8888, VI6_RPF_DSWAP_P_LLS | VI6_RPF_DSWAP_P_LWS |
> > +	  VI6_RPF_DSWAP_P_WDS | VI6_RPF_DSWAP_P_BTS,
> > +	  1, { 32, 0, 0 }, false, false, 1, 1, false },
> 
> 
> So, this is how I interpret the above lines for format BGRA32 (the
> same applies to RGBA32 fwiw)
> 
>         Bytes:          B3      B2      B1      B0
> Input: ARGB8888_1X32:   A       R       G       B

Note that, at the bus level, there's no byte ordering. Data is
transmitted in parallel on a 32-bit bus (at least as far as I know). But
this doesn't matter much anyway.

> Out:   BGRA32           R       G       B       A
> 
> If I apply LLS and LWS on the "Input Row", according to the table I get
> 
>  Position in Table 32.10:    0  1  2  3
>  IN Components ordering:     A  R  G  B  (ARGB8888_1X32
>  Position in Table 32.10:    3  2  1  0  (with LLS and LWS applied)
>  OUT Components ordering:    B  G  R  A
> 
> Which to me is the ordering of components of the format named
> V4L2_PIX_FMT_ARGB32 and not BGRA32 which is instead, as reported RGBA
> (GREAT naming here!)
> 
> What am I doing wrong?

You need to take entry VI6_FMT_RGBA_8888 (0x14) in table 32.10, which
reads R G B A. Applying LLS and LWS but not WDS and BTS swaps the bytes
to A B G R (see table 32.13), so the pixel is written to memory in the A
B G R order, corresponding to V4L2_PIX_FMT_BGRA32 (I agree with you
about the insane naming for the 4CC, but that's not my fault :-().

> >  	{ V4L2_PIX_FMT_ARGB32, MEDIA_BUS_FMT_ARGB8888_1X32,
> >  	  VI6_FMT_ARGB_8888, VI6_RPF_DSWAP_P_LLS | VI6_RPF_DSWAP_P_LWS |
> >  	  VI6_RPF_DSWAP_P_WDS | VI6_RPF_DSWAP_P_BTS,

-- 
Regards,

Laurent Pinchart