linux-kernel - Re: [PATCH 1/3] spi: tegra210-quad: use device_reset_optional() instead of device

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Message-ID: <20250317-solemn-debonair-sambar-f04fa7@leitao>
Date: Mon, 17 Mar 2025 09:56:43 -0700
From: Breno Leitao <leitao@...ian.org>
To: Mark Brown <broonie@...ian.org>
Cc: Thierry Reding <thierry.reding@...il.com>,
	Jonathan Hunter <jonathanh@...dia.com>,
	Sowjanya Komatineni <skomatineni@...dia.com>,
	Laxman Dewangan <ldewangan@...dia.com>, linux-tegra@...r.kernel.org,
	linux-spi@...r.kernel.org, linux-kernel@...r.kernel.org,
	rmikey@...a.com, kernel-team@...a.com
Subject: Re: [PATCH 1/3] spi: tegra210-quad: use device_reset_optional()
 instead of device_reset()

Hello Mark,

On Mon, Mar 17, 2025 at 04:45:31PM +0000, Mark Brown wrote:
> On Mon, Mar 17, 2025 at 08:44:01AM -0700, Breno Leitao wrote:
> > My UEFI machines with tegra210-quad consistently report "device reset
> > failed". Investigation showed this isn't an actual failure
> > - __device_reset() returns -ENOENT because ACPI has no "*_RST" method.
> 
> That's not the case, it's returning an error because there is no reset
> controller discoverable via any mechanism. 
>

Sorry, I was not very familiar with this subsystem, but I chase down
__device_reset(), and I found the return was coming from:

	int __device_reset(struct device *dev, bool optional)
	{
		acpi_handle handle = ACPI_HANDLE(dev);
		if (handle) {
			if (!acpi_has_method(handle, "_RST"))
				return optional ? 0 : -ENOENT;


> There's no specific handling for ACPI here.  

Do you mean no _RST method as stated above?

> It's also not clear that this is a false positive, the
> driver did indeed fail to reset the device and especially for the error
> handling case that seems like relevant information.

If the driver failed to reset the device, then device_reset_optional()
it will return an error code, but it will not return an error code if
the RST method is not found, right?

Sorry, if I am mis-understading the code here.

> At the very least the changelog should be clarified.

What would you add to the changelog to make this clear?

Thanks for the quick review!
--breno