linux-kernel - Re: [PATCH v8] i2c: riic: Implement bus recovery

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Message-ID: <CA+V-a8smaANOtJ9ETNudArHUcwvOAnKB+fEeEFnb_5ioxFSMKw@mail.gmail.com>
Date: Wed, 30 Apr 2025 15:19:00 +0100
From: "Lad, Prabhakar" <prabhakar.csengg@...il.com>
To: Wolfram Sang <wsa+renesas@...g-engineering.com>, 
	"Lad, Prabhakar" <prabhakar.csengg@...il.com>, Chris Brandt <chris.brandt@...esas.com>, 
	Andi Shyti <andi.shyti@...nel.org>, Geert Uytterhoeven <geert+renesas@...der.be>, 
	linux-renesas-soc@...r.kernel.org, linux-i2c@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Biju Das <biju.das.jz@...renesas.com>, 
	Fabrizio Castro <fabrizio.castro.jz@...esas.com>, 
	Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>, 
	Claudiu Beznea <claudiu.beznea.uj@...renesas.com>, Andy Shevchenko <andy@...nel.org>
Subject: Re: [PATCH v8] i2c: riic: Implement bus recovery

Hi Wolfram,

On Fri, Apr 25, 2025 at 10:14 AM Wolfram Sang
<wsa+renesas@...g-engineering.com> wrote:
>
> Hi Prabhakar,
>
> > I prepared a setup on SMARC2 RZ/G3S and I can confirm it is working
>
> This is good news!
>
> > (but this is failing on SMARC RZ/G2L I'll look further into this)
>
> This not so much. Hmmm, are you verifying against the same I2C device
> on the carrier board? If you compare against different I2C devices on
> the module board, the culprit might be the I2C device.
>
You were right, it was the slave indeed. After recovery from the
generic algorithm during the transfer I am seeing arbitration lost due
to which there was a timeout during transmission. So for now we can
conclude the generic I2C recovery algo works for RIIC. I have tested
with two slaves:

- PMOD RTC on SMARC RZ/G2L
- PMOD RTC + Audio codec on SMARC RZ/G3S

After tidying up, I'll resping a new version of the patch.

> > For the SMARC2 RZ/G3S to make sure the I2C GPIO pins behave as
> > opendrain I have the below patch for pinctrl
>
> Do you really need this patch? The GPIO lines are wired to SCL/SDA which
> are already pulled up. Search for R118 in the module schematics.
>
Agreed the pullup isn't needed. This was needed on SMARC RZ/G2L as
there were spikes.

Cheers,
Prabhakar