linux-kernel - Re: [PATCH 2/4] reset: add GPIO-based reset controller

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Date: Thu, 4 Jan 2024 17:11:38 +0100
From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To: Sean Anderson <sean.anderson@...o.com>,
 Bjorn Andersson <andersson@...nel.org>,
 Konrad Dybcio <konrad.dybcio@...aro.org>,
 Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
 Banajit Goswami <bgoswami@...cinc.com>, Liam Girdwood <lgirdwood@...il.com>,
 Mark Brown <broonie@...nel.org>, Rob Herring <robh+dt@...nel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
 Conor Dooley <conor+dt@...nel.org>, Philipp Zabel <p.zabel@...gutronix.de>,
 Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.com>,
 linux-arm-msm@...r.kernel.org, alsa-devel@...a-project.org,
 linux-sound@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org
Cc: Bartosz Golaszewski <brgl@...ev.pl>
Subject: Re: [PATCH 2/4] reset: add GPIO-based reset controller

On 04/01/2024 17:04, Sean Anderson wrote:
> 
>>> Maybe we take the max? But the driver below seems
>>> to only have access to one device. Which I suppose begs the question: how do
>>> we know when it's safe to deassert the reset (e.g. we've gotten to the point
>>> where all devices using this reset gpio have gotten far enough to detect that
>>> they use it)?
>>
>> The driver (reset consumer) knows when it is safe or not. You must
>> implement proper reset handling in your driver.
> 
> The driver has no idea whether it is safe or not. It just calls
> reset_assert/deassert at the appropriate time, and the reset
> framework/controller is supposed to coordinate things so e.g. the device
> doesn't get reset multiple times as multiple drivers all probe.

Hm, wait, now maybe I understand your concern. Did you read the
patchset? This is for the coordinated, shared, non-exclusive reset by
design.  And as stated during previous discussions: that's the driver's
job to be sure it is called like that.

Best regards,
Krzysztof