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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 <ms@dev.tdt.de>
This commit is contained in:
Martin Schiller 2024-05-06 11:01:15 +02:00
parent daa109b42f
commit cffd3ad8d7
1 changed files with 62 additions and 0 deletions
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62
target/linux/lantiq/patches-6.1/0002-MIPS-pci-lantiq-restore-reset-gpio-polarity.patch Normal file
View File

@ -0,0 +1,62 @@
From f038380835033e376d89c72516f087254792bbad Mon Sep 17 00:00:00 2001
From: Martin Schiller <ms@dev.tdt.de>
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: stable@vger.kernel.org
Signed-off-by: Martin Schiller <ms@dev.tdt.de>
---
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;
}