linux-kernel - Re: [PATCH v2 2/2] ARM: dts: at91: disable the nxp,se97b SMBUS timeout on the TSE-850

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Date:   Thu, 30 Nov 2017 13:17:40 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Peter Rosin <peda@...ntia.se>
Cc:     Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
        linux-kernel@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Russell King <linux@...linux.org.uk>,
        Jean Delvare <jdelvare@...e.com>,
        Ludovic Desroches <ludovic.desroches@...rochip.com>,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-hwmon@...r.kernel.org
Subject: Re: [PATCH v2 2/2] ARM: dts: at91: disable the nxp,se97b SMBUS
 timeout on the TSE-850

On Thu, Nov 30, 2017 at 07:46:09PM +0100, Peter Rosin wrote:
> On 2017-11-30 18:26, Alexandre Belloni wrote:
> > On 30/11/2017 at 09:16:38 -0800, Guenter Roeck wrote:
> >> On Wed, Nov 29, 2017 at 09:56:29PM +0100, Alexandre Belloni wrote:
> >>> On 29/11/2017 at 12:53:11 -0800, Guenter Roeck wrote:
> >>>> On Mon, Nov 27, 2017 at 05:31:01PM +0100, Peter Rosin wrote:
> >>>>> The I2C adapter driver is sometimes slow, causing the SCL line to
> >>>>> be stuck low for more than the stipulated SMBUS timeout of 25-35 ms.
> >>>>> This causes the client device to give up which in turn causes silent
> >>>>> corruption of data. So, disable the SMBUS timeout in the client device.
> >>>>>
> >>>>> Signed-off-by: Peter Rosin <peda@...ntia.se>
> >>>>
> >>>> Acked-by: Guenter Roeck <linux@...ck-us.net>
> >>>>
> >>>> I assume this will be sent upstream through an arm tree.
> >>>>
> >>>
> >>> Yes, I'm applying it right now.
> >>>
> >> Are you going to apply the patch for 4.15, or queue it up for 4.16 ?
> >> I have been arguing with myself if this is a feature or a bug fix.
> >> So far I queued the driver change up for 4.16, but I am open to
> >> applying it to 4.15. Any thoughts ?
> >>
> > 
> > I was wondering that myself. I'm open to have it as a fix in 4.15. Or
> > maybe Peter can send the series to stable if he needs it in 4.14.
> > 
> > Peter, what do you think/want?
> 
> TL;DR Either way is fine.
> 
> I think it's a bugfix; it fixes real problems where the application
> misbehave due to faulty content when reading from an eeprom. I'm
> expecting to make a new release for the hw in question RSN and these
> are the only local patches. So, it would be nice if they made it to
> 4.14.x before my release happens. However, it's not like it's difficult
> to rebase the patches should that backport not happen or take too long.
> 
Good enough for me. I'll send it as a fix for v4.15, with Cc: stable.

Guenter

> The badness started to happen much more frequently due to some timing
> difference affecting the i2c bus driver, but in theory it's a problem
> that has been there from the start. I have just not noticed it before...
> 
> Cheers,
> Peter
> --
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