Re: [PATCH 2/2] arm64: dts: imx8mm: Add i.MX8M Mini Toradex Verdin based Menlo board

From: Tim Harvey <tharvey@gateworks.com>
To: Francesco Dolcini <francesco.dolcini@toradex.com>,
	"marex@denx.de" <marex@denx.de>
Cc: Marcel Ziswiler <marcel.ziswiler@toradex.com>,
	 "linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>,
	 "festevam@denx.de" <festevam@denx.de>,
	"peng.fan@nxp.com" <peng.fan@nxp.com>,
	 "shawnguo@kernel.org" <shawnguo@kernel.org>,
	"linux-imx@nxp.com" <linux-imx@nxp.com>,
	Adam Ford <aford173@gmail.com>
Subject: Re: [PATCH 2/2] arm64: dts: imx8mm: Add i.MX8M Mini Toradex Verdin based Menlo board
Date: Fri, 8 Apr 2022 08:29:15 -0700	[thread overview]
Message-ID: <CAJ+vNU0TN5VdyLbqs6YxKOHDDGgqMB6VZhhdaza3bmTAittnUg@mail.gmail.com> (raw)
In-Reply-To: <20220408084938.GB85970@francesco-nb.int.toradex.com>

On Fri, Apr 8, 2022 at 2:05 AM Francesco Dolcini
<francesco.dolcini@toradex.com> wrote:
>
> On Fri, Apr 08, 2022 at 09:56:09AM +0200, Marcel Ziswiler wrote:
> > On Fri, 2022-04-08 at 08:46 +0200, Francesco Dolcini wrote:
> > > On Thu, Apr 07, 2022 at 10:24:56PM +0200, Marek Vasut wrote:
> > > > +
> > > > +&i2c1 {
> > > > +       /* IMX8MM ERRATA e7805 -- I2C is limited to 384 kHz due to SoC bug */
> > > > +       clock-frequency = <100000>;
> > > should this and the related changes in the other i2c nodes done in the
> > > verdin.dtsi? Marcel? (errata is here:
> > > https://www.nxp.com/docs/en/errata/IMX8MDQLQ_1N14W.pdf)
> >
> > Hehe, good catch. Yeah, we probably should move this one into imx8mm-verdin.dtsi instead. On the other hand, it
> > won't hurt doing it twice resp. this one will always override it like that.
> >
> > Anyway, looks like NXP has not fixed this and is re-using the exact same I2C IP with the same errata (;-p).
>
> It looks like even i.MX7 is affected, and NXP has a quirk in the
> i2c-imx driver [0]
>
> [0] https://source.codeaurora.org/external/imx/linux-imx/commit/drivers/i2c/busses/i2c-imx.c?h=lf-5.15.y&id=493b3892ee156af529796641889ca19b971735d2
>
> Francesco

Francesco and Marek,

Interesting - I've never noticed this errata.

I don't see mention of it in the imx8mm-evk which sets the busses to
400khz, and all the other verdin I2C busses are set to 400khz as well.

Should we address this in the i2c driver in U-Boot (and Linux)
instead? Otherwise, I think all of us board maintainers should be
moving the i2c clock to 100kHz. Its not clear to me what I2C slaves
may be affected by this issue.... perhaps maintainers are only
concerned with things that go off-board?

Best Regards,

Tim

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