linux-kernel - Re: [PATCH RFC] gpiolib: ensure that fwnode is properly set

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Date:   Tue, 15 Nov 2022 17:07:38 +0000
From:   Bryan O'Donoghue <bryan.odonoghue@...aro.org>
To:     Brian Masney <bmasney@...hat.com>, linus.walleij@...aro.org,
        brgl@...ev.pl
Cc:     linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, psodagud@...cinc.com,
        quic_shazhuss@...cinc.com, quic_ppareek@...cinc.com,
        ahalaney@...hat.com, echanude@...hat.com,
        nicolas.dechesne@...aro.org
Subject: Re: [PATCH RFC] gpiolib: ensure that fwnode is properly set

On 14/11/2022 20:29, Brian Masney wrote:
> Note that this is a RFC patch and not meant to be merged. I looked into
> a problem with linux-next-20221110 on the Qualcomm SA8540P automotive
> board (sc8280xp) where the UFS host controller would fail to probe due
> to repeated probe deferrals when trying to get reset-gpios via
> devm_gpiod_get_optional().
> 
> of_get_named_gpiod_flags() returns -EPROBE_DEFER, which is caused by
> of_gpiochip_match_node_and_xlate() returning 0 since the of_xlate function
> pointer is not set for the qcom,sc8280xp-tlmm pinctrl driver. The
> pinctrl driver doesn't define one, so of_gpiochip_add() should
> automatically setup of_gpio_simple_xlate() on it's behalf. This doesn't
> happen since the fwnode member on the struct gpiochip is set to null
> when of_gpiochip_add() is called. Let's work around this by ensuring
> that it's set if available.
> 
> Note that this broke sometime within the last few weeks within
> linux-next and I haven't bisected this. I'm posting this in the hopes
> that someone may know offhand which patch(es) may have broken this.
> 
> Signed-off-by: Brian Masney <bmasney@...hat.com>
> ---
>   drivers/gpio/gpiolib.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index 11fb7ec883e9..8bec66008869 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -678,7 +678,7 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
>   	 * Assign fwnode depending on the result of the previous calls,
>   	 * if none of them succeed, assign it to the parent's one.
>   	 */
> -	gdev->dev.fwnode = dev_fwnode(&gdev->dev) ?: fwnode;
> +	gc->fwnode = gdev->dev.fwnode = dev_fwnode(&gdev->dev) ?: fwnode;
>   
>   	gdev->id = ida_alloc(&gpio_ida, GFP_KERNEL);
>   	if (gdev->id < 0) {

Fixes repeated failure to get GPIO despite the controller having 
successfully probed.

[    6.151075] ov9282 21-0060: failed to get reset gpio -517
[    6.160599] ov9282 21-0060: HW configuration is not supported
[    6.160970] hub 1-1:1.0: USB hub found
[    6.168054] imx412 22-001a: failed to get reset gpio -517
[    6.170710] hub 1-1:1.0: 4 ports detected
[    6.175904] imx412 22-001a: HW configuration is not supported