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

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Message-Id: <20221114202943.2389489-1-bmasney@redhat.com>
Date:   Mon, 14 Nov 2022 15:29:43 -0500
From:   Brian Masney <bmasney@...hat.com>
To:     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: [PATCH RFC] gpiolib: ensure that fwnode is properly set

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) {
-- 
2.38.1