linux-kernel - Re: [PATCH v5 3/4] drm/bridge: Introduce LT9611 DSI to HDMI bridge

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Message-ID: <20200723113912.GA535520@ravnborg.org>
Date:   Thu, 23 Jul 2020 13:39:12 +0200
From:   Sam Ravnborg <sam@...nborg.org>
To:     Vinod Koul <vkoul@...nel.org>
Cc:     Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Rob Clark <robdclark@...il.com>, linux-arm-msm@...r.kernel.org,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        Emil Velikov <emil.l.velikov@...il.com>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        John Stultz <john.stultz@...aro.org>
Subject: Re: [PATCH v5 3/4] drm/bridge: Introduce LT9611 DSI to HDMI bridge

On Thu, Jul 23, 2020 at 04:11:51PM +0530, Vinod Koul wrote:
> Hi Sam, Laurent,
> 
> On 22-07-20, 16:14, Laurent Pinchart wrote:
> > > > +static int lt9611_bridge_attach(struct drm_bridge *bridge,
> > > > +				enum drm_bridge_attach_flags flags)
> > > > +{
> > > > +	struct lt9611 *lt9611 = bridge_to_lt9611(bridge);
> > > > +	int ret;
> > > > +
> > > > +	if (!(flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR)) {
> > > > +		dev_err(lt9611->dev, "Fix bridge driver to make connector optional!");
> > > > +		return -EINVAL;
> > > > +	}
> > >
> > > This should say that the display driver should be fixed.
> > > If a display driver expects this bridge to create the connector
> > > it would not work.
> > 
> > Actually, for new bridge drivers, connector creation should be optional
> > from the start. We don't want a failure in that case, the feature should
> > be implemented.
> 
> Yes this is causing issues for me now !. The patch 4/4 adds support in
> msm/dsi but causes regression on qualcomm laptops with ti-sn65dsi86 eDP
> bridge. I tried to fix that up with changes like Laurent has done for
> adv7511, but it hasnt worked yet for me (remote debug of this is bit
> painful)
> 
> So I am going to drop patch 4 from this series and add support for both
> DRM_BRIDGE_ATTACH_NO_CONNECTOR set and cleared (like we have in adv7511)
> so that it can work in both cases, while I fix all bridge uses of
> msm/dsi and then we can drop these. Does that sound okay to you folks?
Yes, sounds like a good plan.
Only when all display drivers are migrated over can we drop all the
workarounds in the bridge drivers.
I had hoped all users of this bridge was converted - alas that was not
the case.

	Sam