linux-kernel - Re: [PATCH v6 2/3] i2c: tegra: Use internal reset when reset property is not available

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Message-ID: <iqx5wzywy2x66n2y36mx4fckrr7wy4lqu3dsejcovghjtmgoz7@zwslylpivy3q>
Date: Fri, 11 Jul 2025 18:00:45 +0200
From: Andi Shyti <andi.shyti@...nel.org>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Akhil R <akhilrajeev@...dia.com>, digetx@...il.com, 
	jonathanh@...dia.com, ldewangan@...dia.com, linux-i2c@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-tegra@...r.kernel.org, p.zabel@...gutronix.de, 
	thierry.reding@...il.com, conor+dt@...nel.org, devicetree@...r.kernel.org, 
	krzk+dt@...nel.org, robh@...nel.org
Subject: Re: [PATCH v6 2/3] i2c: tegra: Use internal reset when reset
 property is not available

Hi Akhil,

On Thu, Jul 10, 2025 at 04:53:01PM +0300, Andy Shevchenko wrote:
> On Thu, Jul 10, 2025 at 06:42:05PM +0530, Akhil R wrote:
> > For controllers that has an internal software reset, make the reset
> > property optional. This provides and option to use I2C in systems
> > that choose to restrict reset control from Linux or not to implement
> > the ACPI _RST method.
> > 
> > Internal reset was not required when the reset control was mandatory.
> > But on platforms where the resets are outside the control of Linux,
> > this had to be implemented by just returning success from BPMP or with
> > an empty _RST method in the ACPI table, basically ignoring the reset.
> > 
> > While the internal reset is not identical to the hard reset of the
> > controller, this will reset all the internal state of the controller
> > including FIFOs. This may slightly alter the behaviour in systems
> > which were ignoring the reset but it should not cause any functional
> > difference since all the required I2C registers are configured after
> > this reset, just as in boot. Considering that this sequence is hit
> > during the boot or during the I2C recovery path from an error, the
> > internal reset provides a better alternative than just ignoring the
> > reset.
> 
> ...
> 
> I would perhaps expand the comment here to explain ENOENT check and what do we
> do in this case. (Note, no rewriting of the existing, just adding a paragraph)
> 
> 	*
> 	* In case ... we compare with -ENOENT ...
> 	* ...
> 	*/

If you write it here I can expand your comment before merging.

Or if you prefer sending a v7 is still fine.

Thanks,
Andi

> >  	err = device_reset(i2c_dev->dev);
> > +	if (err == -ENOENT)
> > +		err = tegra_i2c_master_reset(i2c_dev);
> 
> >  	WARN_ON_ONCE(err);
> 
> Other that that, LGTM,
> Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> 
> -- 
> With Best Regards,
> Andy Shevchenko
> 
>