[PATCH 2/2] gpio: aspeed: Preserve the pending G7 interrupt status on control writes

[Billy Tsai <billy_tsai@aspeedtech.com>]

On G7 each line has its own control register, and its interrupt status
bit (bit 12) is write-1-to-clear. aspeed_g7_reg_bit_set() updates a
field by reading the control register, replacing that field and writing
the value back. When the line's interrupt is pending, the status bit
reads as 1 and is written back as 1, so updating an unrelated field
such as the interrupt enable, trigger type, direction or debounce
selection also clears the pending interrupt.

Mask out the status bit when composing the value to write, so it is
written as 1 only when the status field itself is being set to ack the
interrupt.

Fixes: b2e861bd1eaf ("gpio: aspeed: Support G7 Aspeed gpio controller")
Cc: stable@vger.kernel.org
Signed-off-by: Billy Tsai <billy_tsai@aspeedtech.com>
---
 drivers/gpio/gpio-aspeed.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/gpio/gpio-aspeed.c b/drivers/gpio/gpio-aspeed.c
index 2482f2ff735d..6e834e83915b 100644
--- a/drivers/gpio/gpio-aspeed.c
+++ b/drivers/gpio/gpio-aspeed.c
@@ -1168,7 +1168,13 @@ static void aspeed_g7_reg_bit_set(struct aspeed_gpio *gpio, unsigned int offset,
 	u32 write_val;
 
 	if (mask) {
-		write_val = (ioread32(addr) & ~(mask)) | field_prep(mask, val);
+		/*
+		 * The interrupt status bit is write-1-to-clear. Keep it zero
+		 * unless it is the field being written, so that updating any
+		 * other field leaves a pending interrupt latched.
+		 */
+		write_val = ioread32(addr) & ~(mask | GPIO_G7_CTRL_IRQ_STS);
+		write_val |= field_prep(mask, val);
 		iowrite32(write_val, addr);
 	}
 }

-- 
2.34.1