Rockchip RK3576 UFS controller uses a dedicated pin to reset the connected
UFS device, which can operate either in a hardware controlled mode or as a
GPIO pin.

Power-on default is GPIO mode, but the boot ROM reconfigures it to a
hardware controlled mode if it uses UFS to load the next boot stage.

Given that existing bindings (and rk3576.dtsi) expect a GPIO-controlled
device reset, request the required pin config explicitly.

This doesn't appear to affect Linux, but it does affect U-boot:

Before:
=> md.l 0x2604b398
2604b398: 00000011 00000000 00000000 00000000  ................
< ... snip ... >
=> ufs init
ufshcd-rockchip ufshc@2a2d0000: [RX, TX]: gear=[3, 3], lane[2, 2], pwr[FASTAUTO_MODE, FASTAUTO_MODE], rate = 2
=> md.l 0x2604b398
2604b398: 00000011 00000000 00000000 00000000  ................

After:
=> md.l 0x2604b398
2604b398: 00000011 00000000 00000000 00000000  ................
< ... snip ...>
=> ufs init
ufshcd-rockchip ufshc@2a2d0000: [RX, TX]: gear=[3, 3], lane[2, 2], pwr[FASTAUTO_MODE, FASTAUTO_MODE], rate = 2
=> md.l 0x2604b398
2604b398: 00000010 00000000 00000000 00000000  ................

(0x2604b398 is the respective pin mux register, with its BIT0 driving the
mode of UFS_RST: unset = GPIO, set = hardware controlled UFS_RST)

This helps ensure that GPIO-driven device reset actually fires when the
system requests it, not when whatever black box magic inside the UFSHC
decides to reset the flash chip.

Cc: stable@vger.kernel.org
Fixes: c75e5e010fef ("scsi: arm64: dts: rockchip: Add UFS support for RK3576 SoC")
Reported-by: Quentin Schulz <redacted>
Signed-off-by: Alexey Charkov <alchark@gmail.com>
---
This has originally surfaced during the review of UFS patches for U-boot
at [1], where it was found that the UFS reset line is not requested to be
configured as GPIO but used as such. This leads in some cases to the UFS
driver appearing to control device resets, while in fact it is the
internal controller logic that drives the reset line (perhaps in
unexpected ways).

Thanks Quentin Schulz for spotting this issue.

[1] https://lore.kernel.org/u-boot/259fc358-f72b-4a24-9a71-ad90f2081335@cherry.de/ (local)
---
  arch/arm64/boot/dts/rockchip/rk3576-pinctrl.dtsi | 7 +++++++
  arch/arm64/boot/dts/rockchip/rk3576.dtsi         | 2 +-
  2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/boot/dts/rockchip/rk3576-pinctrl.dtsi b/arch/arm64/boot/dts/rockchip/rk3576-pinctrl.dtsi
index 0b0851a7e4ea..20cfd3393a75 100644
--- a/arch/arm64/boot/dts/rockchip/rk3576-pinctrl.dtsi
+++ b/arch/arm64/boot/dts/rockchip/rk3576-pinctrl.dtsi

@@ -5228,6 +5228,13 @@ ufs_rst: ufs-rst {
  				/* ufs_rstn */
  				<4 RK_PD0 1 &pcfg_pull_none>;
  		};
+
+		/omit-if-no-ref/
+		ufs_rst_gpio: ufs-rst-gpio {
+			rockchip,pins =
+				/* ufs_rstn */
+				<4 RK_PD0 RK_FUNC_GPIO &pcfg_pull_none>;