linux-kernel - Re: [PATCH v5 1/3] i2c: tegra: Fix reset error handling with ACPI

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Message-ID: <20250704064704.23003-1-akhilrajeev@nvidia.com>
Date: Fri, 4 Jul 2025 12:17:04 +0530
From: Akhil R <akhilrajeev@...dia.com>
To: <andriy.shevchenko@...ux.intel.com>, <p.zabel@...gutronix.de>
CC: <akhilrajeev@...dia.com>, <andi.shyti@...nel.org>, <conor+dt@...nel.org>,
	<devicetree@...r.kernel.org>, <digetx@...il.com>, <jonathanh@...dia.com>,
	<krzk+dt@...nel.org>, <ldewangan@...dia.com>, <linux-i2c@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
	<robh@...nel.org>, <thierry.reding@...il.com>
Subject: Re: [PATCH v5 1/3] i2c: tegra: Fix reset error handling with ACPI

On Thu, 3 Jul 2025 17:11:11 +0300, Andy Shevchenko wrote:

...

>>> I did check that. But device_reset_optional() returns '0' if reset is
>>> not available or when the reset succeeds. Then there is no option to
>>> conditionally trigger the internal reset when the reset is not available.
>>> 
>>> Other option was to do the internal reset unconditionally. But then the
>>> devices that do not have an internal reset will have to skip the reset
>>> silently if the reset property is absent in the device tree (or _RST
>>> method is absent in the ACPI table).
>>> 
>>> Though device_reset() returns error when reset is absent, it looks to
>>> be not so straight-forward to detect from the return value that if there
>>> is an actual error during reset or if the reset is absent.
>> 
>> device_reset() should return -ENOENT if the reset is absent (as opposed
>> to present but somehow broken). If there is any code path where this
>> isn't the case, we should probably fix this.
>> 
>> In the ACPI case, -ENOENT is returned by __device_reset() if the "_RST"
>> method is not found.
>> 
>> In the OF case, -ENOENT is returned by __of_reset_control_get() if the
>> requested id can't be found in a "reset-names" property, or if
>> of_parse_phandle_with_args() returns -ENOENT for the "resets" (or
>> "reset-gpios") property - that is, when this property doesn't exist or
>> the entry indicated by the reset id is empty.
>
> I have nothing to add to what Philipp just said. I believe we don't want
> open coded variant of the device_reset*().

Agree and makes sense. Will update the code as below and will separate the
change in two patches similar to this version. Hope it looks good.

	err = device_reset(i2c_dev->dev);
	if (err == -ENOENT)
		err = tegra_i2c_master_reset(i2c_dev);
	
	WARN_ON_ONCE(err);

Best Regards,
Akhil