Re: FYI: i.MX8MP ISP (RKISP1) MI registers corruption: resolved

From: Alexander Stein <alexander.stein@ew.tq-group.com>
To: "Adam Ford" <aford173@gmail.com>, "Krzysztof Hałasa" <khalasa@piap.pl>
Cc: Stefan Klug <stefan.klug@ideasonboard.com>,
	Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
	Dafna Hirschfeld <dafna@fastmail.com>,
	Heiko Stuebner <heiko@sntech.de>,
	Paul Elder <paul.elder@ideasonboard.com>,
	Jacopo Mondi <jacopo.mondi@ideasonboard.com>,
	Ondrej Jirman <megi@xff.cz>,
	linux-media@vger.kernel.org, linux-rockchip@lists.infradead.org,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: Re: FYI: i.MX8MP ISP (RKISP1) MI registers corruption: resolved
Date: Tue, 02 Sep 2025 13:23:20 +0200	[thread overview]
Message-ID: <5921855.DvuYhMxLoT@steina-w> (raw)
In-Reply-To: <m31popxjqk.fsf@t19.piap.pl>

Am Dienstag, 2. September 2025, 11:54:27 CEST schrieb Krzysztof Hałasa:
> Hi,
> 
> summary:
> 
> I've done a few additional tests and it seems the MEDIA_AXI clock is the
> problem. Reducing it to 400 MHz while still running MEDIA_ISP at 500 MHz
> produces no errors.
> MEDIA_ISP at 400 MHz and MEDIA_AXI at 500 MHz produces errors, though
> (register address errors while reading and writing from/to ISP MI
> (memory interface) registers, only on the secondary ISP (isp1), and
> generally only while streaming data from the ISP).
> 
> What is driven by MEDIA_AXI clock root? MEDIAMIX: ISI, LCDIF, ISP, DWE.
> 
> According to both datasheets (industrial and commercial), MEDIA_AXI
> is limited to 400 MHz in normal mode and 500 MHz in overdrive mode.
> All my hardware is setup for overdrive mode, though (two manufacturers,
> both using the same PMIC setup).
> 
> Since no hardware in the official Linux kernel tree (DT) uses the second
> ISP... Should we just add a warning to the imx8mp.dtsi and be done with
> it?
> Out of tree hardware using isp1 (csi1) obviously exists.

There is also [1] which addresses normal mode and clock limits. I don't know
if there is any progress.

Best regards
Alexander

[1] https://lore.kernel.org/all/20250218-imx8m-clk-v4-2-b7697dc2dcd0@pengutronix.de/

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