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

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Message-Id: <b3da27ce-161b-4462-a608-c36f4b0696ce@app.fastmail.com>
Date: Tue, 18 Mar 2025 20:00:05 +0100
From: "Arnd Bergmann" <arnd@...db.de>
To: "Breno Leitao" <leitao@...ian.org>, "Mark Brown" <broonie@...ian.org>
Cc: "Thierry Reding" <thierry.reding@...il.com>,
 "Jon 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, "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
 noodles@...th.li, "Jarkko Sakkinen" <jarkko@...nel.org>,
 "Peter Huewe" <peterhuewe@....de>, jgg@...pe.c
Subject: Re: [PATCH 1/3] spi: tegra210-quad: use device_reset_optional() instead of
 device_reset()

On Tue, Mar 18, 2025, at 19:32, Breno Leitao wrote:
> On Tue, Mar 18, 2025 at 11:29:26AM -0700, Breno Leitao wrote:
>> On Tue, Mar 18, 2025 at 05:34:55PM +0000, Mark Brown wrote:
>> 
>> Summary of the proiblem: tpm_tis is trying to read random numbers
>> through a dead SPI controller. That causes infinite amounts of warnings
>> on the kernel, given that the controller is WARNing on time outs (which
>> is being fixed in one of the patches in this patchset).
>> 
>> Question: Should tpm_tis be aware that the underneath SPI controller is
>> dead, and eventually get unplugged?
>
> Adding Arnd to the email.

Hi Breno,

That does sound like the easiest answer: if the spi controller driver
knows that it needs a reset but there is no reset controller, shutting
itself down and removing its child devices seems like the least
offensive action.

No idea if there are other spi controllers that do something like this.

      Arnd