linux-kernel - Re: [PATCH] media: imx335: Fix reset-gpio handling

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Message-ID: <172224852603.392292.14437094530843053506@ping.linuxembedded.co.uk>
Date: Mon, 29 Jul 2024 11:22:06 +0100
From: Kieran Bingham <kieran.bingham@...asonboard.com>
To: Sakari Ailus <sakari.ailus@...ux.intel.com>, Umang Jain <umang.jain@...asonboard.com>
Cc: linux-media@...r.kernel.org, open list <linux-kernel@...r.kernel.org>, Tommaso Merciai <tomm.merciai@...il.com>
Subject: Re: [PATCH] media: imx335: Fix reset-gpio handling

Quoting Sakari Ailus (2024-07-29 09:54:01)
> Hi Umang,
> 
> On Mon, Jul 29, 2024 at 02:19:32PM +0530, Umang Jain wrote:
> > Hi Sakari
> > 
> > On 29/07/24 1:11 pm, Sakari Ailus wrote:
> > > Hi Umang,
> > > 
> > > Thanks for the patch.
> > > 
> > > On Mon, Jul 29, 2024 at 11:35:35AM +0530, Umang Jain wrote:
> > > > The imx335 reset-gpio is initialised with GPIO_OUT_LOW during probe.
> > > Should it be initialised to high instead, to enable reset?
> > 
> > This initialization matches the physical line status, which is low in this
> > case.
> 
> Documentation/driver-api/gpio/consumer.rst:
> 
>         * GPIOD_OUT_LOW to initialize the GPIO as output with a value of 0.
> 
> ...
> 
>         Note that the initial value is *logical* and the physical line
>         level depends on whether the line is configured active high or
>         active low (see :ref:`active_low_semantics`).
> 

Yes, I think this patch should also update/fix the call in
imx335_parse_hw_config()

	/* Request optional reset pin */
	imx335->reset_gpio = devm_gpiod_get_optional(imx335->dev, "reset",
-						     GPIOD_OUT_LOW);
+						     GPIOD_OUT_HIGH);

To make sure it starts off in reset until it's set accordingly in
imx335_power_{on,off}()

--
Kieran


> -- 
> Sakari Ailus