linux-kernel - [PATCH] MIPS: pci: lantiq: restore reset gpio polarity

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Date: Fri,  7 Jun 2024 11:04:00 +0200
From: Martin Schiller <ms@....tdt.de>
To: hauke@...ke-m.de,
	dmitry.torokhov@...il.com,
	tsbogend@...ha.franken.de,
	rdunlap@...radead.org,
	robh@...nel.org,
	bhelgaas@...gle.com
Cc: linux-mips@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Martin Schiller <ms@....tdt.de>,
	stable@...r.kernel.org
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: stable@...r.kernel.org
Signed-off-by: Martin Schiller <ms@....tdt.de>
---
 arch/mips/pci/pci-lantiq.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/mips/pci/pci-lantiq.c b/arch/mips/pci/pci-lantiq.c
index 68a8cefed420..0844db34022e 100644
--- a/arch/mips/pci/pci-lantiq.c
+++ b/arch/mips/pci/pci-lantiq.c
@@ -124,14 +124,14 @@ static int ltq_pci_startup(struct platform_device *pdev)
 		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 platform_device *pdev)

 	/* 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;
 }
-- 
2.39.2