linux-kernel - Re: [PATCH v4 4/6] reset: Instantiate reset GPIO controller for shared reset-gpios

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Date: Tue, 23 Jan 2024 16:58:01 +0100
From: Philipp Zabel <p.zabel@...gutronix.de>
To: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>, 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>,
 "Rafael J. Wysocki" <rafael@...nel.org>, Viresh Kumar
 <viresh.kumar@...aro.org>, Frank Rowand <frowand.list@...il.com>, 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,  linux-pm@...r.kernel.org
Cc: Bartosz Golaszewski <brgl@...ev.pl>, Chris Packham
 <chris.packham@...iedtelesis.co.nz>, Sean Anderson <sean.anderson@...o.com>
Subject: Re: [PATCH v4 4/6] reset: Instantiate reset GPIO controller for
 shared reset-gpios

On Di, 2024-01-23 at 15:13 +0100, Krzysztof Kozlowski wrote:
> Devices sharing a reset GPIO could use the reset framework for
> coordinated handling of that shared GPIO line.  We have several cases of
> such needs, at least for Devicetree-based platforms.
> 
> If Devicetree-based device requests a reset line, while "resets"
> Devicetree property is missing but there is a "reset-gpios" one,
> instantiate a new "reset-gpio" platform device which will handle such
> reset line.  This allows seamless handling of such shared reset-gpios
> without need of changing Devicetree binding [1].
> 
> To avoid creating multiple "reset-gpio" platform devices, store the
> Devicetree "reset-gpios" GPIO specifiers used for new devices on a
> linked list.  Later such Devicetree GPIO specifier (phandle to GPIO
> controller, GPIO number and GPIO flags) is used to check if reset
> controller for given GPIO was already registered.
> 
> If two devices have conflicting "reset-gpios" property, e.g. with
> different ACTIVE_xxx flags, this would allow to spawn two separate
> "reset-gpio" devices, where the second would fail probing on busy GPIO
> request.
> 
> Link: https://lore.kernel.org/all/YXi5CUCEi7YmNxXM@robh.at.kernel.org/ [1]
> Cc: Bartosz Golaszewski <brgl@...ev.pl>
> Cc: Chris Packham <chris.packham@...iedtelesis.co.nz>
> Cc: Sean Anderson <sean.anderson@...o.com>
> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
> 
> ---
> 
> Depends on previous of change.
> ---
>  drivers/reset/core.c             | 213 +++++++++++++++++++++++++++++--
>  include/linux/reset-controller.h |   4 +
>  2 files changed, 204 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/reset/core.c b/drivers/reset/core.c
> index 4d5a78d3c085..6e81b8d35055 100644
> --- a/drivers/reset/core.c
> +++ b/drivers/reset/core.c
> @@ -10,9 +10,13 @@

Oh, and

#include <linux/cleanup.h>

>  #include <linux/export.h>
>  #include <linux/kernel.h>
>  #include <linux/kref.h>
> +#include <linux/gpio/driver.h>
> +#include <linux/gpio/machine.h>
> +#include <linux/idr.h>
>  #include <linux/module.h>
>  #include <linux/of.h>
>  #include <linux/acpi.h>
> +#include <linux/platform_device.h>
>  #include <linux/reset.h>
>  #include <linux/reset-controller.h>
>  #include <linux/slab.h>

regards
Philipp