linux-kernel - [PATCH] gpio: spacemit-k1: Use PDR for pin direction, not SDR/CDR

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Message-Id: <20260127-gpio-spacemit-k1-pdr-v1-1-bb868a517dbc@iscas.ac.cn>
Date: Tue, 27 Jan 2026 10:58:49 +0800
From: Vivian Wang <wangruikang@...as.ac.cn>
To: Linus Walleij <linusw@...nel.org>, 
 Bartosz Golaszewski <brgl@...nel.org>, Yixun Lan <dlan@...too.org>, 
 Alex Elder <elder@...cstar.com>
Cc: Bartosz Golaszewski <brgl@...ev.pl>, linux-gpio@...r.kernel.org, 
 linux-riscv@...ts.infradead.org, spacemit@...ts.linux.dev, 
 linux-kernel@...r.kernel.org, Vivian Wang <wangruikang@...as.ac.cn>
Subject: [PATCH] gpio: spacemit-k1: Use PDR for pin direction, not SDR/CDR

On the SpacemiT GPIO controller, the direction control register PDR is
readable and writable [1]. Therefore, implement direction control by
using PDR as dirout, and don't mark it as unreadable.

The original implementation, using SDR as dirout and CDR as dirin, is
not actually a supported configuration by gpio-mmio. The hardware
supports changing the direction of some pins atomically by writing a
value with the corresponding bits set to SDR (set as output) or to CDR
(set as input). However, gpio-mmio does not actually handle this.

Using only PDR as dirout to match the expectations of gpio-mmio. This
also allows us to avoid clobbering potentially important GPIO direction
configurations set by pre-Linux boot stages.

Found while trying to add PCIe support to OrangePi RV2, where the
regulator (controlled by GPIO 116) turns off on boot while some other
GPIO pin in the same bank is touched, which is not desirable.

Link: https://developer.spacemit.com/documentation?token=Rn9Kw3iFHirAMgkIpTAcV2Arnkf#18.4-gpio # [1]
Fixes: d00553240ef8 ("gpio: spacemit: add support for K1 SoC")
Signed-off-by: Vivian Wang <wangruikang@...as.ac.cn>
---
Tested on K1 only - help with K3 testing would be appreciated.

Backporting this looks like it would be annoying. Unsure about whether
it would be necessary.

Of course the PCIe 3.3V regulator still needs to described properly in
the future DTS update for OrangePi RV2, but IIUC this avoids having the
regulator briefly powering off? In any case, being able to read the
direction is still an improvement.
---
 drivers/gpio/gpio-spacemit-k1.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/drivers/gpio/gpio-spacemit-k1.c b/drivers/gpio/gpio-spacemit-k1.c
index 8f570a1a4894..dbd2e81094b9 100644
--- a/drivers/gpio/gpio-spacemit-k1.c
+++ b/drivers/gpio/gpio-spacemit-k1.c
@@ -199,7 +199,7 @@ static int spacemit_gpio_add_bank(struct spacemit_gpio *sg,
 	struct gpio_chip *gc = &gb->chip.gc;
 	struct device *dev = sg->dev;
 	struct gpio_irq_chip *girq;
-	void __iomem *dat, *set, *clr, *dirin, *dirout;
+	void __iomem *dat, *set, *clr, *dirout;
 	int ret;
 
 	gb->base = regs + sg->data->bank_offsets[index];
@@ -208,8 +208,7 @@ static int spacemit_gpio_add_bank(struct spacemit_gpio *sg,
 	dat	= gb->base + to_spacemit_gpio_regs(gb)[SPACEMIT_GPLR];
 	set	= gb->base + to_spacemit_gpio_regs(gb)[SPACEMIT_GPSR];
 	clr	= gb->base + to_spacemit_gpio_regs(gb)[SPACEMIT_GPCR];
-	dirin	= gb->base + to_spacemit_gpio_regs(gb)[SPACEMIT_GCDR];
-	dirout	= gb->base + to_spacemit_gpio_regs(gb)[SPACEMIT_GSDR];
+	dirout	= gb->base + to_spacemit_gpio_regs(gb)[SPACEMIT_GPDR];
 
 	config = (struct gpio_generic_chip_config) {
 		.dev = dev,
@@ -218,9 +217,7 @@ static int spacemit_gpio_add_bank(struct spacemit_gpio *sg,
 		.set = set,
 		.clr = clr,
 		.dirout = dirout,
-		.dirin = dirin,
-		.flags = GPIO_GENERIC_UNREADABLE_REG_SET |
-			 GPIO_GENERIC_UNREADABLE_REG_DIR,
+		.flags = GPIO_GENERIC_UNREADABLE_REG_SET,
 	};
 
 	/* This registers 32 GPIO lines per bank */

---
base-commit: 3a6a36a3fc4e18e202eaf6c258553b5a17b91677
change-id: 20260127-gpio-spacemit-k1-pdr-d71588b6dd90

Best regards,
-- 
Vivian "dramforever" Wang