[PATCH] pinctrl: rockchip: fix rk3288 gpio0 pull up configuration

[Sonny Rao]

On rk3288, for gpio bank 0, the registers which configure pull-ups
don't implement the enable bits in the upper half of the register,
unlike the other gpio configuration registers, and so the kernel
must perform a read-modify-write of the register to update a
particular gpio's pull up settings in that bank.

The current code is actually clobbering the contents of the register,
so this fixes it by using regmap_update_bits and masking out only the
bits which require updating.  In the case of gpio0 on rk3288 the upper
enable bits will just get ignored, and the other configurations won't
get clobbered.

Signed-off-by: Sonny Rao <sonnyrao at chromium.org>
---
 drivers/pinctrl/pinctrl-rockchip.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/pinctrl/pinctrl-rockchip.c b/drivers/pinctrl/pinctrl-rockchip.c
index 5e8b2e0..bd00ae9 100644
--- a/drivers/pinctrl/pinctrl-rockchip.c
+++ b/drivers/pinctrl/pinctrl-rockchip.c
@@ -722,7 +722,7 @@ static int rockchip_set_pull(struct rockchip_pin_bank *bank,
 	int reg, ret;
 	unsigned long flags;
 	u8 bit;
-	u32 data;
+	u32 data, mask;
 
 	dev_dbg(info->dev, "setting pull of GPIO%d-%d to %d\n",
 		 bank->bank_num, pin_num, pull);
@@ -751,6 +751,14 @@ static int rockchip_set_pull(struct rockchip_pin_bank *bank,
 		/* enable the write to the equivalent lower bits */
 		data = ((1 << RK3188_PULL_BITS_PER_PIN) - 1) << (bit + 16);
 
+		/*
+		 * on rk3288, gpio bank 0 doesn't support the write enable, and
+		 * upper 16 bit are always zero, so we create a mask which will
+		 * only update the bits we want in the lower 16, while still
+		 * preserving write enable bits in upper 16.
+		 */
+		mask = data | (data >> 16);
+
 		switch (pull) {
 		case PIN_CONFIG_BIAS_DISABLE:
 			break;
@@ -770,7 +778,7 @@ static int rockchip_set_pull(struct rockchip_pin_bank *bank,
 			return -EINVAL;
 		}
 
-		ret = regmap_write(regmap, reg, data);
+		ret = regmap_update_bits(regmap, reg, mask, data);
 
 		spin_unlock_irqrestore(&bank->slock, flags);
 		break;
-- 
1.8.3.2