linux-kernel - Re: drm/bridge/imx8mp-hdmi-tx: Allow inexact pixel clock frequencies (Was: [PATCH V8 10/12] drm/bridge: imx: add bridge wrapper driver for i.MX8MP DWC HDMI)

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Date: Tue, 18 Jun 2024 09:04:44 +0900
From: Dominique MARTINET <dominique.martinet@...ark-techno.com>
To: Adam Ford <aford173@...il.com>, Lucas Stach <l.stach@...gutronix.de>
Cc: linux-arm-kernel@...ts.infradead.org, marex@...x.de,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Andrzej Hajda <andrzej.hajda@...el.com>,
	Neil Armstrong <neil.armstrong@...aro.org>,
	Robert Foss <rfoss@...nel.org>, Jonas Karlman <jonas@...boo.se>,
	Jernej Skrabec <jernej.skrabec@...il.com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>,
	Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>,
	NXP Linux Team <linux-imx@....com>, Vinod Koul <vkoul@...nel.org>,
	Kishon Vijay Abraham I <kishon@...nel.org>,
	Liu Ying <victor.liu@....com>, dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org, linux-phy@...ts.infradead.org,
	Makoto Sato <makoto.sato@...ark-techno.com>
Subject: Re: drm/bridge/imx8mp-hdmi-tx: Allow inexact pixel clock frequencies
 (Was: [PATCH V8 10/12] drm/bridge: imx: add bridge wrapper driver for
 i.MX8MP DWC HDMI)

Dominique MARTINET wrote on Tue, Jun 18, 2024 at 08:45:38AM +0900:
> I'm thinking the last few values just affect a very small % of the
> values, but would need to check with a proper scope if I can get a hold
> of the clock line...
> Does any of you happen to have any datasheet for these registers,
> or should we consider them to be magic values?

Answering to myself on this point, the registers are properly described
in the iMX8MP reference manual...
I don't make much sense of it at this point (what's SDC..?), but I guess
it does sound likely we could generate the values with some work.

I'll wait for replies a bit first in case one of you understands this
better than I (which is quite likely!), but can give this a few more
hours to help.

-- 
Dominique