[PATCH] reset: core: honour optional resets when the GPIO fallback is unusable

[hsyysy]

From: Yang Siyuan <hsyysy@xxxxxxx>

__fwnode_reset_control_get() honours RESET_CONTROL_FLAGS_BIT_OPTIONAL for
every failure source except the reset-gpio fallback: when
__reset_add_reset_gpio_device() fails, the error is returned even for an
optional reset.

This is reachable on Allwinner SoCs, whose pinctrl uses three-cell GPIO
specifiers. The reset-gpio fallback only supports two cells, so it
returns -ENOENT and a consumer asking for an optional reset fails to
probe instead of falling back to its own GPIO handling. mmc-pwrseq-simple
on the Anbernic RG35XX family hits this: its wifi_pwrseq node has
reset-gpios but no resets, so the SDIO WiFi adapter never probes.

Keep propagating -EPROBE_DEFER, since the GPIO provider may be available
later, but treat any other failure as "no reset" when the request is
optional.

Fixes: c721f189e89c ("reset: Instantiate reset GPIO controller for shared reset-gpios")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Yang Siyuan <hsyysy@xxxxxxx>
---
 drivers/reset/core.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/reset/core.c b/drivers/reset/core.c
index 38e189d04..f2375dd17 100644
--- a/drivers/reset/core.c
+++ b/drivers/reset/core.c
@@ -1181,7 +1181,17 @@ __fwnode_reset_control_get(struct fwnode_handle *fwnode, const char *id, int ind
 		ret = __reset_add_reset_gpio_device(fwnode, &args);
 		if (ret) {
 			fwnode_handle_put(args.fwnode);
-			return ERR_PTR(ret);
+
+			/*
+			 * The GPIO provider may just not be available yet, so
+			 * EPROBE_DEFER must always be propagated. Any other
+			 * failure means that the fallback cannot be used,
+			 * which is not an error for an optional reset.
+			 */
+			if (ret == -EPROBE_DEFER || !optional)
+				return ERR_PTR(ret);
+
+			return NULL;
 		}
 	}
 
base-commit: 091b06388b117fefdcb63336ac09956a4914b961
-- 
2.56.0