Re: [PATCH v2 4/6] drm/msm/dsi: add a comment to explain pkt_per_line encoding

[Jonathan Marek]

On 11/15/23 2:38 AM, Dmitry Baryshkov wrote:
> On Wed, 15 Nov 2023 at 01:00, Jonathan Marek <jonathan@xxxxxxxx> wrote:
> > Make it clear why the pkt_per_line value is being "divided by 2".
> >
> > Signed-off-by: Jonathan Marek <jonathan@xxxxxxxx>
> > ---
> >   drivers/gpu/drm/msm/dsi/dsi_host.c | 2 ++
> >   1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c
> > index 66f198e21a7e..842765063b1b 100644
> > --- a/drivers/gpu/drm/msm/dsi/dsi_host.c
> > +++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
> > @@ -877,6 +877,8 @@ static void dsi_update_dsc_timing(struct msm_dsi_host *msm_host, bool is_cmd_mod
> >          /* DSI_VIDEO_COMPRESSION_MODE & DSI_COMMAND_COMPRESSION_MODE
> >           * registers have similar offsets, so for below common code use
> >           * DSI_VIDEO_COMPRESSION_MODE_XXXX for setting bits
> > +        *
> > +        * pkt_per_line is log2 encoded, >>1 works for supported values (1,2,4)
> >           */
> >          reg |= DSI_VIDEO_COMPRESSION_MODE_CTRL_PKT_PER_LINE(pkt_per_line >> 1);
>
> Should we switch to ffs() or fls() instead?

Just a ffs() on its own can be confusing as well (without the 
information that only powers of two are possible), I think like this is 
better.

> >          reg |= DSI_VIDEO_COMPRESSION_MODE_CTRL_EOL_BYTE_NUM(eol_byte_num);
> > --
> > 2.26.1