net: fec: add post PHY reset delay DT property

Some PHY require to wait for a bit after the reset GPIO has been
toggled. This adds support for the DT property `phy-reset-post-delay`
which gives the delay in milliseconds to wait after reset.

If the DT property is not given, no delay is observed. Post reset delay
greater than 1000ms are invalid.

Signed-off-by: Quentin Schulz <quentin.schulz@free-electrons.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Acked-by: Fugang Duan <fugang.duan@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/devicetree/bindings/net/fsl-fec.txt

@@ -15,6 +15,10 @@ Optional properties:
 - phy-reset-active-high : If present then the reset sequence using the GPIO
   specified in the "phy-reset-gpios" property is reversed (H=reset state,
   L=operation state).
+- phy-reset-post-delay : Post reset delay in milliseconds. If present then
+  a delay of phy-reset-post-delay milliseconds will be observed after the
+  phy-reset-gpios has been toggled. Can be omitted thus no delay is
+  observed. Delay is in range of 1ms to 1000ms. Other delays are invalid.
 - phy-supply : regulator that powers the Ethernet PHY.
 - phy-handle : phandle to the PHY device connected to this device.
 - fixed-link : Assume a fixed link. See fixed-link.txt in the same directory.

drivers/net/ethernet/freescale/fec_main.c

@@ -3192,7 +3192,7 @@ static int fec_reset_phy(struct platform_device *pdev)
 {
 	int err, phy_reset;
 	bool active_high = false;
-	int msec = 1;
+	int msec = 1, phy_post_delay = 0;
 	struct device_node *np = pdev->dev.of_node;
 
 	if (!np)
@@ -3209,6 +3209,11 @@ static int fec_reset_phy(struct platform_device *pdev)
 	else if (!gpio_is_valid(phy_reset))
 		return 0;
 
+	err = of_property_read_u32(np, "phy-reset-post-delay", &phy_post_delay);
+	/* valid reset duration should be less than 1s */
+	if (!err && phy_post_delay > 1000)
+		return -EINVAL;
+
 	active_high = of_property_read_bool(np, "phy-reset-active-high");
 
 	err = devm_gpio_request_one(&pdev->dev, phy_reset,
@@ -3226,6 +3231,15 @@ static int fec_reset_phy(struct platform_device *pdev)
 
 	gpio_set_value_cansleep(phy_reset, !active_high);
 
+	if (!phy_post_delay)
+		return 0;
+
+	if (phy_post_delay > 20)
+		msleep(phy_post_delay);
+	else
+		usleep_range(phy_post_delay * 1000,
+			     phy_post_delay * 1000 + 1000);
+
 	return 0;
 }
 #else /* CONFIG_OF */