[PATCH] drm/bridge: lontium-lt8912b: Do not generate HFP

[PATCH] drm/bridge: lontium-lt8912b: Do not generate HFP

[max.oss.09]

From: Max Krummenacher <max.krummenacher@toradex.com>

The datasheet of lontium-lt8912b doesn't require blanking during
the HFP period. Thus use LP during HFP.

Tested with a samsung-dsim (i.MX8 MM) and a tc358768 DPI to DSI bridge
as the DSI host.

Signed-off-by: Max Krummenacher <max.krummenacher@toradex.com>

---

 drivers/gpu/drm/bridge/lontium-lt8912b.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/bridge/lontium-lt8912b.c b/drivers/gpu/drm/bridge/lontium-lt8912b.c
index 3e49d855b364..760d89493276 100644
--- a/drivers/gpu/drm/bridge/lontium-lt8912b.c
+++ b/drivers/gpu/drm/bridge/lontium-lt8912b.c
@@ -494,6 +494,7 @@ static int lt8912_attach_dsi(struct lt8912 *lt)
 
 	dsi->mode_flags = MIPI_DSI_MODE_VIDEO |
 			  MIPI_DSI_MODE_LPM |
+			  MIPI_DSI_MODE_VIDEO_NO_HFP |
 			  MIPI_DSI_MODE_NO_EOT_PACKET;
 
 	ret = devm_mipi_dsi_attach(dev, dsi);
-- 
2.42.0

Re: [PATCH] drm/bridge: lontium-lt8912b: Do not generate HFP

[Francesco Dolcini]

Hello all,

On Mon, Jul 28, 2025 at 05:00:50PM +0200, max.oss.09@gmail.com wrote:
> From: Max Krummenacher <max.krummenacher@toradex.com>
> 
> The datasheet of lontium-lt8912b doesn't require blanking during
> the HFP period. Thus use LP during HFP.
> 
> Tested with a samsung-dsim (i.MX8 MM) and a tc358768 DPI to DSI bridge
> as the DSI host.
> 
> Signed-off-by: Max Krummenacher <max.krummenacher@toradex.com>

Just a gently ping on this

Francesco

Re: [PATCH] drm/bridge: lontium-lt8912b: Do not generate HFP

[Max Krummenacher]

On Thu, Sep 11, 2025 at 05:34:53PM +0200, Francesco Dolcini wrote:
> Hello all,
> 
> On Mon, Jul 28, 2025 at 05:00:50PM +0200, max.oss.09@gmail.com wrote:
> > From: Max Krummenacher <max.krummenacher@toradex.com>
> > 
> > The datasheet of lontium-lt8912b doesn't require blanking during
> > the HFP period. Thus use LP during HFP.
> > 
> > Tested with a samsung-dsim (i.MX8 MM) and a tc358768 DPI to DSI bridge
> > as the DSI host.
> > 
> > Signed-off-by: Max Krummenacher <max.krummenacher@toradex.com>
> 
> Just a gently ping on this

Any opinion on this?
Max

> 
> Francesco

Re: [PATCH] drm/bridge: lontium-lt8912b: Do not generate HFP

[Francesco Dolcini]

+Dmitry, Luca

Hello all,
how to get this patch considered and eventually merged? I see that this
is not moving since long.

Considering that Adrien Grassein is not visible on the mailing list
since 2022, and that I have various HW available that is using this
combination (on TI Sitara and Jacinto, on a DPI-DSI tc358768 bridge,
and NXP i.MX), I have access to the (little) documentation that is
available from Lontium I can propose myself as a maintainer here.

I assume being able to ack patches would help the maintenance here, or
is this just a glitch and a ping was enough?

Dmitry, Luca: looking at the recent commits you are the one who merged
the most patches on drivers/gpu/drm/bridge lately, what's you advise?

Francesco

On Mon, Jul 28, 2025 at 05:00:50PM +0200, max.oss.09@gmail.com wrote:
> From: Max Krummenacher <max.krummenacher@toradex.com>
> 
> The datasheet of lontium-lt8912b doesn't require blanking during
> the HFP period. Thus use LP during HFP.
> 
> Tested with a samsung-dsim (i.MX8 MM) and a tc358768 DPI to DSI bridge
> as the DSI host.
> 
> Signed-off-by: Max Krummenacher <max.krummenacher@toradex.com>
> 
> ---
> 
>  drivers/gpu/drm/bridge/lontium-lt8912b.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/gpu/drm/bridge/lontium-lt8912b.c b/drivers/gpu/drm/bridge/lontium-lt8912b.c
> index 3e49d855b364..760d89493276 100644
> --- a/drivers/gpu/drm/bridge/lontium-lt8912b.c
> +++ b/drivers/gpu/drm/bridge/lontium-lt8912b.c
> @@ -494,6 +494,7 @@ static int lt8912_attach_dsi(struct lt8912 *lt)
>  
>  	dsi->mode_flags = MIPI_DSI_MODE_VIDEO |
>  			  MIPI_DSI_MODE_LPM |
> +			  MIPI_DSI_MODE_VIDEO_NO_HFP |
>  			  MIPI_DSI_MODE_NO_EOT_PACKET;
>  
>  	ret = devm_mipi_dsi_attach(dev, dsi);
> -- 
> 2.42.0
> 

Re: [PATCH] drm/bridge: lontium-lt8912b: Do not generate HFP

[Luca Ceresoli]

Hi Francesco,

On Wed Apr 29, 2026 at 3:33 PM CEST, Francesco Dolcini wrote:
> +Dmitry, Luca
>
> Hello all,
> how to get this patch considered and eventually merged? I see that this
> is not moving since long.
>
> Considering that Adrien Grassein is not visible on the mailing list
> since 2022, and that I have various HW available that is using this
> combination (on TI Sitara and Jacinto, on a DPI-DSI tc358768 bridge,
> and NXP i.MX), I have access to the (little) documentation that is
> available from Lontium I can propose myself as a maintainer here.

Thanks for volunteering! I am not a DRM maintainer, so I'll let others
chime in, but I suspect you should just send a patch to add yourself to the
MAINTAINERS entry and (as a separate patch?) remove Adrien, unless he
speaks up by then.

> I assume being able to ack patches would help the maintenance here, or
> is this just a glitch and a ping was enough?

dri-devel is flooded by patches, driver-specific ones will unavoidably be
missed in lack of a responsive maintainer. So this is not a glitch, it's a
frequent pattern I'm afraid.

As above, if you were in the MAINTAINERS entry, look at patches and comment
on them, and test on hardware that would be great IMHO.

For this one patch: it looks OK.

Reviewed-by: Luca Ceresoli <luca.ceresoli@bootlin.com>

Adding the "why" would be better, which I assume to be power saving. No
need to sned a v2 just for that though.

I'm applying it in ~1 week. It would be good if you could check it still
applies on drm-misc-next before that, report back if it does, send a v2
(adding the "why") if it doesn't.

Luca

--
Luca Ceresoli, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

Re: [PATCH] drm/bridge: lontium-lt8912b: Do not generate HFP

[Adrien Grassein]

Hello Francesco and all;

Thank you for proposing yourself.

I have no time anymore to maintain this driver (and I don't have the
setup anymore).

I totally agree with this proposal.

Thanks a lot,
Adrien

Le jeu. 30 avr. 2026 à 09:53, Luca Ceresoli
<luca.ceresoli@bootlin.com> a écrit :
>
> Hi Francesco,
>
> On Wed Apr 29, 2026 at 3:33 PM CEST, Francesco Dolcini wrote:
> > +Dmitry, Luca
> >
> > Hello all,
> > how to get this patch considered and eventually merged? I see that this
> > is not moving since long.
> >
> > Considering that Adrien Grassein is not visible on the mailing list
> > since 2022, and that I have various HW available that is using this
> > combination (on TI Sitara and Jacinto, on a DPI-DSI tc358768 bridge,
> > and NXP i.MX), I have access to the (little) documentation that is
> > available from Lontium I can propose myself as a maintainer here.
>
> Thanks for volunteering! I am not a DRM maintainer, so I'll let others
> chime in, but I suspect you should just send a patch to add yourself to the
> MAINTAINERS entry and (as a separate patch?) remove Adrien, unless he
> speaks up by then.
>
> > I assume being able to ack patches would help the maintenance here, or
> > is this just a glitch and a ping was enough?
>
> dri-devel is flooded by patches, driver-specific ones will unavoidably be
> missed in lack of a responsive maintainer. So this is not a glitch, it's a
> frequent pattern I'm afraid.
>
> As above, if you were in the MAINTAINERS entry, look at patches and comment
> on them, and test on hardware that would be great IMHO.
>
> For this one patch: it looks OK.
>
> Reviewed-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
>
> Adding the "why" would be better, which I assume to be power saving. No
> need to sned a v2 just for that though.
>
> I'm applying it in ~1 week. It would be good if you could check it still
> applies on drm-misc-next before that, report back if it does, send a v2
> (adding the "why") if it doesn't.
>
> Luca
>
> --
> Luca Ceresoli, Bootlin
> Embedded Linux and Kernel engineering
> https://bootlin.com

Re: [PATCH] drm/bridge: lontium-lt8912b: Do not generate HFP

[Francesco Dolcini]

On Thu, Apr 30, 2026 at 09:53:08AM +0200, Luca Ceresoli wrote:
> Hi Francesco,
> 
> On Wed Apr 29, 2026 at 3:33 PM CEST, Francesco Dolcini wrote:
> > +Dmitry, Luca
> >
> > Hello all,
> > how to get this patch considered and eventually merged? I see that this
> > is not moving since long.
> >
> > Considering that Adrien Grassein is not visible on the mailing list
> > since 2022, and that I have various HW available that is using this
> > combination (on TI Sitara and Jacinto, on a DPI-DSI tc358768 bridge,
> > and NXP i.MX), I have access to the (little) documentation that is
> > available from Lontium I can propose myself as a maintainer here.
> 
> Thanks for volunteering! I am not a DRM maintainer, so I'll let others
> chime in, but I suspect you should just send a patch to add yourself to the
> MAINTAINERS entry and (as a separate patch?) remove Adrien, unless he
> speaks up by then.

Separate patch coming, thanks.

> I'm applying it in ~1 week. It would be good if you could check it still
> applies on drm-misc-next before that, report back if it does

It applies cleanly.

Thanks!
Francesco

Re: [PATCH] drm/bridge: lontium-lt8912b: Do not generate HFP

[Luca Ceresoli]

On Mon, 28 Jul 2025 17:00:50 +0200, max.oss.09@gmail.com wrote:
> The datasheet of lontium-lt8912b doesn't require blanking during
> the HFP period. Thus use LP during HFP.
> 
> Tested with a samsung-dsim (i.MX8 MM) and a tc358768 DPI to DSI bridge
> as the DSI host.
> 
> 
> [...]

Applied, thanks!

[1/1] drm/bridge: lontium-lt8912b: Do not generate HFP
      commit: 9a56caf49525e8a0ee349fb69db101d018a95a66

Best regards,
-- 
Luca Ceresoli <luca.ceresoli@bootlin.com>