lantiq: add patch to fix the reset gpio handling in the pci driver

Linux kernel commit 90c2d2eb7ab5 ("MIPS: pci: lantiq: switch to using
gpiod API") not only switched to the gpiod API, but also inverted /
changed the polarity of the GPIO.

According to the PCI specification, the RST# pin is an active-low
signal. However, most of the device trees that have been widely used for
a long time (mainly in the openWrt project) define this GPIO as
active-high and the old driver code inverted the signal internally.

Apparently there are actually boards where the reset gpio must be
operated inverted. For this reason, we cannot use the GPIOD_OUT_LOW/HIGH
flag for initialization. Instead, we must explicitly set the gpio to
value 1 in order to take into account any "GPIO_ACTIVE_LOW" flag that
may have been set.

In order to remain compatible with all these existing device trees, we
should therefore keep the logic as it was before the commit.

Signed-off-by: Martin Schiller <[email protected]>

target/linux/lantiq/patches-6.1/0002-MIPS-pci-lantiq-restore-reset-gpio-polarity.patch

@@ -0,0 +1,62 @@
+From f038380835033e376d89c72516f087254792bbad Mon Sep 17 00:00:00 2001
+From: Martin Schiller <[email protected]>
+Date: Mon, 6 May 2024 09:41:42 +0200
+Subject: [PATCH] MIPS: pci: lantiq: restore reset gpio polarity
+
+Commit 90c2d2eb7ab5 ("MIPS: pci: lantiq: switch to using gpiod API") not
+only switched to the gpiod API, but also inverted / changed the polarity
+of the GPIO.
+
+According to the PCI specification, the RST# pin is an active-low
+signal. However, most of the device trees that have been widely used for
+a long time (mainly in the openWrt project) define this GPIO as
+active-high and the old driver code inverted the signal internally.
+
+Apparently there are actually boards where the reset gpio must be
+operated inverted. For this reason, we cannot use the GPIOD_OUT_LOW/HIGH
+flag for initialization. Instead, we must explicitly set the gpio to
+value 1 in order to take into account any "GPIO_ACTIVE_LOW" flag that
+may have been set.
+
+In order to remain compatible with all these existing device trees, we
+should therefore keep the logic as it was before the commit.
+
+Fixes: 90c2d2eb7ab5 ("MIPS: pci: lantiq: switch to using gpiod API")
+Cc: [email protected]
+Signed-off-by: Martin Schiller <[email protected]>
+---
+ arch/mips/pci/pci-lantiq.c | 8 ++++----
+ 1 file changed, 4 insertions(+), 4 deletions(-)
+
+--- a/arch/mips/pci/pci-lantiq.c
++++ b/arch/mips/pci/pci-lantiq.c
+@@ -124,14 +124,14 @@ static int ltq_pci_startup(struct platfo
+ 		clk_disable(clk_external);
+
+ 	/* setup reset gpio used by pci */
+-	reset_gpio = devm_gpiod_get_optional(&pdev->dev, "reset",
+-					     GPIOD_OUT_LOW);
++	reset_gpio = devm_gpiod_get_optional(&pdev->dev, "reset", GPIOD_ASIS);
+ 	error = PTR_ERR_OR_ZERO(reset_gpio);
+ 	if (error) {
+ 		dev_err(&pdev->dev, "failed to request gpio: %d\n", error);
+ 		return error;
+ 	}
+ 	gpiod_set_consumer_name(reset_gpio, "pci_reset");
++	gpiod_direction_output(reset_gpio, 1);
+
+ 	/* enable auto-switching between PCI and EBU */
+ 	ltq_pci_w32(0xa, PCI_CR_CLK_CTRL);
+@@ -194,10 +194,10 @@ static int ltq_pci_startup(struct platfo
+
+ 	/* toggle reset pin */
+ 	if (reset_gpio) {
+-		gpiod_set_value_cansleep(reset_gpio, 1);
++		gpiod_set_value_cansleep(reset_gpio, 0);
+ 		wmb();
+ 		mdelay(1);
+-		gpiod_set_value_cansleep(reset_gpio, 0);
++		gpiod_set_value_cansleep(reset_gpio, 1);
+ 	}
+ 	return 0;
+ }