Re: [PATCH v3 6/7] drm/kmb: Enable ADV bridge after modeset

[Sam Ravnborg <sam@ravnborg.org>]

Hi Anitha,

On Wed, Oct 13, 2021 at 04:36:31PM -0700, Anitha Chrisanthus wrote:
> On KMB, ADV bridge must be programmed and powered on prior to
> MIPI DSI HW initialization.
> 
> Fixes: 98521f4d4b4c ("drm/kmb: Mipi DSI part of the display driver")
> Signed-off-by: Anitha Chrisanthus <anitha.chrisanthus@intel.com>

> ---
>  drivers/gpu/drm/kmb/kmb_dsi.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/gpu/drm/kmb/kmb_dsi.c b/drivers/gpu/drm/kmb/kmb_dsi.c
> index a0669b842ff5..7ab6b7b44cbc 100644
> --- a/drivers/gpu/drm/kmb/kmb_dsi.c
> +++ b/drivers/gpu/drm/kmb/kmb_dsi.c
> @@ -1341,6 +1341,7 @@ static void connect_lcd_to_mipi(struct kmb_dsi *kmb_dsi)
>  		return;
>  	}
>  
> +	drm_bridge_chain_enable(adv_bridge);

Do not use drm_bridge_chain_enable(). If you really need to do this hack
use the atomic variant. The one you use here is about to be deleted.

That said - I expect this to be a workaround for some design issue.
One bridge driver should not need to power on another bridge, the
infrastructure should take care.
I know we did not make kmb_dsi a proper bridge, but this may be the time
to do it so we avoid such a workaround and the driver will then be able
to use the bridge infrastructure as it is supposed to do.

	Sam

>  	/* DISABLE MIPI->CIF CONNECTION */
>  	regmap_write(msscam, MSS_MIPI_CIF_CFG, 0);
>  
> -- 
> 2.25.1