linux-kernel - Re: [PATCH v2] i2c: omap: Fix standard mode false ACK readings

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Message-ID: <20240913140934.29bb542b@akair>
Date: Fri, 13 Sep 2024 14:09:34 +0200
From: Andreas Kemnade <andreas@...nade.info>
To: "H. Nikolaus Schaller" <hns@...delico.com>
Cc: Reid Tonking <reidt@...com>, Tony Lindgren <tony@...mide.com>,
 "Raghavendra, Vignesh" <vigneshr@...com>, Aaro Koskinen
 <aaro.koskinen@....fi>, Janusz Krzysztofik <jmkrzyszt@...il.com>,
 Linux-OMAP <linux-omap@...r.kernel.org>, linux-i2c@...r.kernel.org, Linux
 Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] i2c: omap: Fix standard mode false ACK readings

Am Wed, 11 Sep 2024 11:40:04 +0200
schrieb "H. Nikolaus Schaller" <hns@...delico.com>:

> Hi,
> 
> > Am 28.04.2023 um 20:30 schrieb Reid Tonking <reidt@...com>:
> > 
> > On 10:43-20230428, Tony Lindgren wrote:  
> >> * Raghavendra, Vignesh <vigneshr@...com> [230427 13:18]:  
> >>> On 4/27/2023 1:19 AM, Reid Tonking wrote:  
> >>>> Using standard mode, rare false ACK responses were appearing with
> >>>> i2cdetect tool. This was happening due to NACK interrupt
> >>>> triggering ISR thread before register access interrupt was
> >>>> ready. Removing the NACK interrupt's ability to trigger ISR
> >>>> thread lets register access ready interrupt do this instead.  
> >> 
> >> So is it safe to leave NACK interrupt unhandled until we get the
> >> next interrupt, does the ARDY always trigger after hitting this?
> >> 
> >> Regards,
> >> 
> >> Tony  
> > 
> > Yep, the ARDY always gets set after a new command when register
> > access is ready so there's no need for NACK interrupt to control
> > this.  
> 
> I have tested one GTA04A5 board where this patch breaks boot on
> v4.19.283 or v6.11-rc7 (where it was inherited from some earlier -rc
> series).
> 
> The device is either stuck with no signs of activity or reports RCU
> stalls after a 20 second pause.
> 
cannot reproduce it here. I had a patch to disable 1Ghz on that
device in my tree. Do you have anything strange in your
tree?

Regards,
Andreas