linux-kernel - Re: [PATCH v4 2/3] i2c: tegra: make reset an optional property

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Message-ID: <qhrsdrtq4qeyntpqz4edu6uj25hxqdxlc5a25pexw7mj3iuwi3@35vrlxvkl6kq>
Date: Tue, 10 Jun 2025 11:56:27 +0200
From: Thierry Reding <thierry.reding@...il.com>
To: Akhil R <akhilrajeev@...dia.com>
Cc: 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, 
	p.zabel@...gutronix.de, robh@...nel.org
Subject: Re: [PATCH v4 2/3] i2c: tegra: make reset an optional property

On Tue, Jun 10, 2025 at 03:21:57PM +0530, Akhil R wrote:
[...]
> >> diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
[...]
> >> @@ -621,8 +641,10 @@ static int tegra_i2c_init(struct tegra_i2c_dev *i2c_dev)
> >>  	 */
> >>  	if (handle)
> >>  		err = acpi_evaluate_object(handle, "_RST", NULL, NULL);
> >
> > How is the internal reset handled on ACPI? Does the _RST method do the
> > internal reset?
> 
> Right now, devices using ACPI would have to rely on the _RST method implementation.
> It is unlikely that it implements an internal reset mechanism.
> 
> Do you suggest adding a check with 'acpi_has_method(handle, "_RST")' and fallback to
> internal reset when it is false?

I don't know if that's desirable (because _RST may be left unimplemented
on purpose on an ACPI platform, and using the internal reset may break
something), but yeah, that would be the equivalent of the DT path.

Thierry

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