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

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Message-ID: <20250612153338.68829-1-akhilrajeev@nvidia.com>
Date: Thu, 12 Jun 2025 21:03:38 +0530
From: Akhil R <akhilrajeev@...dia.com>
To: <andriy.shevchenko@...ux.intel.com>
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>,
	<p.zabel@...gutronix.de>, <robh@...nel.org>, <thierry.reding@...il.com>
Subject: Re: [PATCH v4 2/3] i2c: tegra: make reset an optional property

On Thu, 12 Jun 2025 15:55:21 +0300, Andy Shevchenko wrote:

>
>> >  static int tegra_i2c_init(struct tegra_i2c_dev *i2c_dev)
>> >  {
>> >     u32 val, clk_divisor, clk_multiplier, tsu_thd, tlow, thigh, non_hs_mode;
>> > @@ -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);
>> > -   else
>> > +   else if (i2c_dev->rst)
>> >             err = reset_control_reset(i2c_dev->rst);
>> > +   else
>> > +           err = tegra_i2c_master_reset(i2c_dev);
>>
>> Can you please take a look here? Should the reset happen in ACPI?
>
> This is a good question. Without seeing all the implementations of _RST method
> for the platforms based on this SoC it's hard to say. Ideally the _RST (which
> is called above) must handle it properly, but firmwares have bugs...
>
> TL;DR: I think the approach is correct, and if any bug in ACPI will be found,
> the workaround (quirk) needs to be added here later on.

As in Thierry's comment, I was in thought of updating the code as below.
Does it make sense or would it be better keep what it is there now?

if (handle && acpi_has_method(handle, "_RST"))
	err = acpi_evaluate_object(handle, "_RST", NULL, NULL);
else if (i2c_dev->rst)
	err = reset_control_reset(i2c_dev->rst);
else
	err = tegra_i2c_master_reset(i2c_dev);

Regards,
Akhil