linux-kernel - Re: drm/bridge: adv7511: Attach next bridge without creating connector

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Date: Mon, 13 May 2024 18:49:59 +0200
From: Robert Foss <rfoss@...nel.org>
To: Sui Jingfeng <suijingfeng@...c.ac.cn>
Cc: Liu Ying <victor.liu@....com>, dri-devel@...ts.freedesktop.org, 
	linux-kernel@...r.kernel.org, andrzej.hajda@...el.com, 
	neil.armstrong@...aro.org, Laurent.pinchart@...asonboard.com, jonas@...boo.se, 
	jernej.skrabec@...il.com, maarten.lankhorst@...ux.intel.com, 
	mripard@...nel.org, tzimmermann@...e.de, airlied@...il.com, daniel@...ll.ch, 
	dmitry.baryshkov@...aro.org, biju.das.jz@...renesas.com, aford173@...il.com, 
	bli@...g-olufsen.dk, robh@...nel.org, jani.nikula@...el.com
Subject: Re: drm/bridge: adv7511: Attach next bridge without creating connector

On Mon, May 13, 2024 at 6:30 PM Sui Jingfeng <suijingfeng@...c.ac.cn> wrote:
>
> Hi,
>
>
> On 5/13/24 16:02, Liu Ying wrote:
> > The connector is created by either this ADV7511 bridge driver or
> > any DRM device driver/previous bridge driver, so this ADV7511
> > bridge driver should not let the next bridge driver create connector.
> >
> > If the next bridge is a HDMI connector, the next bridge driver
> > would fail to attach bridge from display_connector_attach() without
> > the DRM_BRIDGE_ATTACH_NO_CONNECTOR flag.
> >
> > Add that flag to drm_bridge_attach() function call in
> > adv7511_bridge_attach() to fix the issue.
> >
> > This fixes the issue where the HDMI connector bridge fails to attach
> > to the previous ADV7535 bridge on i.MX8MP EVK platform:
> >
> > [    2.216442] [drm:drm_bridge_attach] *ERROR* failed to attach bridge /hdmi-connector to encoder None-37: -22
> > [    2.220675] mmc1: SDHCI controller on 30b50000.mmc [30b50000.mmc] using ADMA
> > [    2.226262] [drm:drm_bridge_attach] *ERROR* failed to attach bridge /soc@...us@...00000/i2c@...30000/hdmi@3d to encoder None-37: -22
> > [    2.245204] [drm:drm_bridge_attach] *ERROR* failed to attach bridge /soc@...us@...00000/dsi@...60000 to encoder None-37: -22
> > [    2.256445] imx-lcdif 32e80000.display-controller: error -EINVAL: Failed to attach bridge for endpoint0
> > [    2.265850] imx-lcdif 32e80000.display-controller: error -EINVAL: Cannot connect bridge
> > [    2.274009] imx-lcdif 32e80000.display-controller: probe with driver imx-lcdif failed with error -22
> >
> > Fixes: 14b3cdbd0e5b ("drm/bridge: adv7511: make it honour next bridge in DT")
> > Signed-off-by: Liu Ying <victor.liu@....com>
> > ---
> >   drivers/gpu/drm/bridge/adv7511/adv7511_drv.c | 3 ++-
> >   1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> > index dd21b81bd28f..66ccb61e2a66 100644
> > --- a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> > +++ b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> > @@ -953,7 +953,8 @@ static int adv7511_bridge_attach(struct drm_bridge *bridge,
> >       int ret = 0;
> >
> >       if (adv->next_bridge) {
> > -             ret = drm_bridge_attach(bridge->encoder, adv->next_bridge, bridge, flags);
> > +             ret = drm_bridge_attach(bridge->encoder, adv->next_bridge, bridge,
> > +                                     flags | DRM_BRIDGE_ATTACH_NO_CONNECTOR);
>
> As a side note, I think, maybe you could do better in the future.
>
> If we know that the KMS display driver side has the HDMI connector
> already created for us, we should pass DRM_BRIDGE_ATTACH_NO_CONNECTOR
> from the root KMS driver side. Which is to forbidden all potential
> drm bridge drivers to create a connector in the middle.
>
> The KMS display driver side could parse the DT to know if there is
> a hdmi connector, or merely just hdmi connector device node, or
> something else.
>
> However, other maintainer and/or reviewer's opinion are of cause
> more valuable. I send a A-b because I thought the bug is urgency
> and it's probably more important to solve this bug first. And
> maybe you can Cc: <stable@...r.kernel.org> if you like.
>

Reviewed-by: Robert Foss <rfoss@...nel.org>