net: phy: mdio-gpio: Fix working over slow can_sleep GPIOs

This commit re-enables support for slow GPIO pins. It was initially
introduced by commit 2d6c9091ab76 ("net: mdio-gpio: support access that
may sleep") and got lost by commit 7e5fbd1e0700 ("net: mdio-gpio:
Convert to use gpiod functions where possible").

Also add a warning about slow GPIO pins like it is done in i2c-gpio.

Signed-off-by: Martin Schiller <ms@dev.tdt.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/phy/mdio-gpio.c

@@ -63,7 +63,7 @@ static void mdio_dir(struct mdiobb_ctrl *ctrl, int dir)
 		 * assume the pin serves as pull-up. If direction is
 		 * output, the default value is high.
 		 */
-		gpiod_set_value(bitbang->mdo, 1);
+		gpiod_set_value_cansleep(bitbang->mdo, 1);
 		return;
 	}
 
@@ -78,7 +78,7 @@ static int mdio_get(struct mdiobb_ctrl *ctrl)
 	struct mdio_gpio_info *bitbang =
 		container_of(ctrl, struct mdio_gpio_info, ctrl);
 
-	return gpiod_get_value(bitbang->mdio);
+	return gpiod_get_value_cansleep(bitbang->mdio);
 }
 
 static void mdio_set(struct mdiobb_ctrl *ctrl, int what)
@@ -87,9 +87,9 @@ static void mdio_set(struct mdiobb_ctrl *ctrl, int what)
 		container_of(ctrl, struct mdio_gpio_info, ctrl);
 
 	if (bitbang->mdo)
-		gpiod_set_value(bitbang->mdo, what);
+		gpiod_set_value_cansleep(bitbang->mdo, what);
 	else
-		gpiod_set_value(bitbang->mdio, what);
+		gpiod_set_value_cansleep(bitbang->mdio, what);
 }
 
 static void mdc_set(struct mdiobb_ctrl *ctrl, int what)
@@ -97,7 +97,7 @@ static void mdc_set(struct mdiobb_ctrl *ctrl, int what)
 	struct mdio_gpio_info *bitbang =
 		container_of(ctrl, struct mdio_gpio_info, ctrl);
 
-	gpiod_set_value(bitbang->mdc, what);
+	gpiod_set_value_cansleep(bitbang->mdc, what);
 }
 
 static const struct mdiobb_ops mdio_gpio_ops = {
@@ -162,6 +162,10 @@ static int mdio_gpio_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
+	if (gpiod_cansleep(bitbang->mdc) || gpiod_cansleep(bitbang->mdio) ||
+	    gpiod_cansleep(bitbang->mdo))
+		dev_warn(&pdev->dev, "Slow GPIO pins might wreak havoc into MDIO bus timing");
+
 	if (pdev->dev.of_node) {
 		bus_id = of_alias_get_id(pdev->dev.of_node, "mdio-gpio");
 		if (bus_id < 0) {