[RFC] drm: omapdrm: dsi: add refsel also for omap4

Some 3.0 source has it set behind a if (omap4).
Maybe it is helpful maybe not, at least in the omap4460
trm these bits are marked as reserved.
But maybe some dsi video mode panel starts magically working.

Signed-off-by: Andreas Kemnade <andreas@kemnade.info>
---
 drivers/gpu/drm/omapdrm/dss/dsi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

* Andreas Kemnade <andreas@kemnade.info> [230913 06:59]:
> Some 3.0 source has it set behind a if (omap4).
> Maybe it is helpful maybe not, at least in the omap4460
> trm these bits are marked as reserved.
> But maybe some dsi video mode panel starts magically working.

Interesting. So Andreas mentioned that dsi video mode works on omap5
but not on omap4. Adding Sebastian to the list too.

Regards,

Tony

> 
> Signed-off-by: Andreas Kemnade <andreas@kemnade.info>
> ---
>  drivers/gpu/drm/omapdrm/dss/dsi.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/omapdrm/dss/dsi.c b/drivers/gpu/drm/omapdrm/dss/dsi.c
> index 60189a23506a1..e2f576cd9f63c 100644
> --- a/drivers/gpu/drm/omapdrm/dss/dsi.c
> +++ b/drivers/gpu/drm/omapdrm/dss/dsi.c
> @@ -4505,7 +4505,7 @@ static const struct dss_pll_hw dss_omap4_dsi_pll_hw = {
>  	.has_stopmode = true,
>  	.has_freqsel = false,
>  	.has_selfreqdco = false,
> -	.has_refsel = false,
> +	.has_refsel = true,
>  };
>  
>  static const struct dss_pll_hw dss_omap5_dsi_pll_hw = {
> -- 
> 2.39.2
>

* Tomi Valkeinen <tomi.valkeinen@ideasonboard.com> [230913 12:11]:
> I'm somewhat sure that the upstream driver used to work on omap4 sdp, which
> has two DSI panels. But I can't even remember what omap4 version it had.

I think those were both dsi command mode panels though, not video mode?

Regards,

Tony

On 13/09/2023 15:48, Tony Lindgren wrote:
> * Tomi Valkeinen <tomi.valkeinen@ideasonboard.com> [230913 12:11]:
>> I'm somewhat sure that the upstream driver used to work on omap4 sdp, which
>> has two DSI panels. But I can't even remember what omap4 version it had.
> 
> I think those were both dsi command mode panels though, not video mode?

Yes, true. If the PLL is totally wrong due to refsel, I'm sure a command 
mode panel would also fail. But it's true that video mode panels are 
more sensitive to the clock rate.

  Tomi

On Wed, 13 Sep 2023 15:11:08 +0300
Tomi Valkeinen <tomi.valkeinen@ideasonboard.com> wrote:

> On 13/09/2023 09:59, Andreas Kemnade wrote:
> > Some 3.0 source has it set behind a if (omap4).
> > Maybe it is helpful maybe not, at least in the omap4460
> > trm these bits are marked as reserved.
> > But maybe some dsi video mode panel starts magically working.  
> 
> Sorry, what does this mean? That this fixes something, or you are
> just guessing?
> 
just diffing registers between good and bad. It does not fix anything,
just reducing the diff.

> I'm somewhat sure that the upstream driver used to work on omap4 sdp, 
> which has two DSI panels. But I can't even remember what omap4
> version it had.
> 
after we are using displays from gpu/drm/displays?

Regards
Andreas

Am Wed, 13 Sep 2023 15:58:11 +0300
schrieb Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>:

> On 13/09/2023 15:48, Tony Lindgren wrote:
> > * Tomi Valkeinen <tomi.valkeinen@ideasonboard.com> [230913 12:11]:  
> >> I'm somewhat sure that the upstream driver used to work on omap4
> >> sdp, which has two DSI panels. But I can't even remember what
> >> omap4 version it had.  
> > 
> > I think those were both dsi command mode panels though, not video
> > mode?  
> 
> Yes, true. If the PLL is totally wrong due to refsel, I'm sure a
> command mode panel would also fail. But it's true that video mode
> panels are more sensitive to the clock rate.
> 
hmm, still analyzing:
What works:
  OMAP5 + Pyra (Videomode display requiring some init commands) 
  some command mode stuff with OMAP4 (droid4)
 
What does not work:
  OMAP4 with some dsi videomode to something else (LVDS/DPI) converter
       if init commands are sent through dsi, then these commands fail
       with bta sync problems.

So sending init commands to video mode displays seems not to be a
principal problem.
But looking deeper at the drivers, there seem to be commands sent
to the converters to configure lanes on that side, e.g.
tc358762_write(ctx, DSI_LANEENABLE,
                       LANEENABLE_L0EN | LANEENABLE_CLEN);

There might be trouble if these are not sent in low power mode.

So probably the next analyzing step would be to check if things
are really sent in low power mode.

Regards,
Andreas