linux-kernel - Re: imx8mm lcdif->dsi->adv7535 no video, no errors

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Message-ID: <20220803055602.b5x7ekgm54x45r5n@pengutronix.de>
Date:   Wed, 3 Aug 2022 07:56:02 +0200
From:   Marco Felsch <m.felsch@...gutronix.de>
To:     Adam Ford <aford173@...il.com>
Cc:     Fabio Estevam <festevam@...il.com>, Marek Vasut <marex@...x.de>,
        Stefan Agner <stefan@...er.ch>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Jonas Karlman <jonas@...boo.se>,
        David Airlie <airlied@...ux.ie>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Neil Armstrong <narmstrong@...libre.com>,
        NXP Linux Team <linux-imx@....com>,
        Robert Foss <robert.foss@...aro.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        arm-soc <linux-arm-kernel@...ts.infradead.org>,
        Jagan Teki <jagan@...rulasolutions.com>, robert.chiras@....com,
        laurentiu.palcu@....com
Subject: Re: imx8mm lcdif->dsi->adv7535 no video, no errors

Hi Adam,

sorry for the delay.

On 22-08-02, Adam Ford wrote:

...

> > > I think that the most important one is the blanking calc. Can you try to
> > > revert "drm/bridge: adv7511: Repair bus_flags and bus_format" and check
> > > if you can get a output still? Also something to try would be to disable
> > > the internal timing generator by specifying
> > > 'adi,disable-timing-generator'. Also if you have an oscilloscope for
> 
> I did some reading about the internal timing generator.  It appears
> that it's required when video formats use fractional bytes, and it's
> preconfigured to run at 720p by default, but registers 28h through 37h
> configure it for other video modes.

I thought this timing generator can detect the sync timing
automatically. Also I saw some mail discussions where this timing
generator can trigger missbehaviours. Since we send the sync packages
from the dsi-host to the ADV, I think it should be possible for the ADV
to reconstruct the sync signals without the need of the internal timing
generator.

> Are you thinking the imx8mm DSI generator would do it better?

You mean the porches we are sending?

Regards,
  Marco