linux-kernel - Re: [PATCH v1 1/1] platform/x86: int3472: discrete: Remap "reset" to "enable" for OV7251

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <ae68cba8-564c-47bf-a796-2bf15b3998d6@redhat.com>
Date: Mon, 26 Aug 2024 17:12:44 +0200
From: Hans de Goede <hdegoede@...hat.com>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
 Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
 platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: Daniel Scally <djrscally@...il.com>
Subject: Re: [PATCH v1 1/1] platform/x86: int3472: discrete: Remap "reset" to
 "enable" for OV7251

Hi Andy,

On 8/21/24 8:40 PM, Andy Shevchenko wrote:
> The driver of OV7251 expects "enable" pin instead of "reset".
> Remap "reset" to "enable" and update polarity.
> 
> In particular, the Microsoft Surface Book can't load the camera sensor
> driver without this change:
> 
>  ov7251 i2c-INT347E:00: supply vdddo not found, using dummy regulator
>  ov7251 i2c-INT347E:00: supply vddd not found, using dummy regulator
>  ov7251 i2c-INT347E:00: supply vdda not found, using dummy regulator
>  ov7251 i2c-INT347E:00: cannot get enable gpio
>  ov7251 i2c-INT347E:00: probe with driver ov7251 failed with error -2
> 
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> ---
> 
> Hmm... I have spent some time to achieve this, and then I realised that
> linux-surface GitHub project already has something similar [1].
> 
> The advantage of [1] is that it applies the quirk to all OV7251 sensors
> on the platform (don't know how useful it IRL).
> 
> However, it seems the [1] has two issues:
> 1) it missed terminator entry in the ACPI ID table;
> 2) it forces polarity to be active high, while I think the XOR approach
> is better as it's possible (but quite unlikely I believe) that reset pin
> might be inverted on the PCB level.
> 
> All in all, I'm fine with any of these patches to be applied with the
> above mentioned improvements / caveats.
> 
> Link: https://github.com/linux-surface/kernel/commit/d0f2c2d5a449c2bf69432f90d164183143d8af8d [1]

Looking at the datasheet the sensor actually has a reset pin and not
an enable pin and the current GPIO mapping in the ov7251 driver /
device-tree bindings is wrong.

The datasheet describes the single reset control pin as:

D6 XSHUTDOWN input "reset (active low with internal pull down resistor)"

So as we have done before I would greatly prefer for the sensor driver
to get fixed instead of hacking around this in the int3472 code.

You could do something similar to what is done in the ov2680.c driver
for this, here is the ov2680 gpiod-get code adjusted for the ov7251 case:

        /*
         * The device-tree bindings call this pin "enable", but the
	 * datasheet describes the pin as "reset (active low with internal
	 * pull down resistor)". The ACPI tables describing this sensor
	 * on e.g. the Microsoft Surface Book use the ACPI equivalent of
	 * "reset" as pin name, which ACPI glue code then maps to "reset".
 	 * Check for a "reset" pin if there is no "enable" pin.
         */
	ov7251->enable_gpio = devm_gpiod_get(dev, "enable", GPIOD_OUT_HIGH);
	if (IS_ERR(ov7251->enable_gpio)) {
		ov7251->enable_gpio = devm_gpiod_get(dev, "reset", GPIOD_OUT_LOW);
		if (!IS_ERR(ov7251->enable_gpio))
			gpiod_toggle_active_low(ov7251->enable_gpio);
	}
	if (IS_ERR(ov7251->enable_gpio)) {
                dev_err(dev, "cannot get enable gpio\n");
                return PTR_ERR(ov7251->enable_gpio);
        }

(untested)

Regards,

Hans



> 
>  drivers/platform/x86/intel/int3472/discrete.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/platform/x86/intel/int3472/discrete.c b/drivers/platform/x86/intel/int3472/discrete.c
> index b5f6f71bb1dd..0559295dfb27 100644
> --- a/drivers/platform/x86/intel/int3472/discrete.c
> +++ b/drivers/platform/x86/intel/int3472/discrete.c
> @@ -86,6 +86,16 @@ static int skl_int3472_map_gpio_to_sensor(struct int3472_discrete_device *int347
>  		return -EINVAL;
>  	}
>  
> +	/*
> +	 * The driver of OV7251 expects "enable" pin instead of "reset".
> +	 * Remap "reset" to "enable" and update polarity.
> +	 */
> +	if (!strcmp(int3472->sensor_name, "i2c-INT347E:00") &&
> +	    !strcmp(func, "reset")) {
> +		func = "enable";
> +		polarity ^= GPIO_ACTIVE_LOW;
> +	}
> +
>  	ret = skl_int3472_fill_gpiod_lookup(&int3472->gpios.table[int3472->n_sensor_gpios],
>  					    agpio, func, polarity);
>  	if (ret)