[PATCH net-next v2 2/2] net: dsa: mxl-gsw1xx: reset the switch through reset-gpios

[Joseph Telaak via B4 Relay]

From: Joseph Telaak <joseph@xxxxxxxxxx>

The switch keeps the configuration the bootloader left in it, and the
driver never resets it. The MDIO core asserts and releases reset-gpios
only for PHY devices, so a reset line described on the switch node has
no effect either.

On the GL.iNet GL-SFT1200 the bootloader leaves each internal PHY of
the GSW150 one MDIO address above its port. Port 0 then fails with
"failed to connect to PHY: -ENODEV", and the PHY that answers at a
port's address belongs to the neighboring port. After a hardware reset
every PHY is back at its port's address and all ports work.

Get the reset through the reset controller API and pulse it before the
first register access. The reset core hands a reset-gpios property to
the reset-gpio driver, so a board that wires the reset this way needs
CONFIG_RESET_GPIO; without it the reset is skipped. The timing follows
the vendor's driver for the GSW150: asserted for 250 ms, then 1 s before
the switch is accessed.

Signed-off-by: Joseph Telaak <joseph@xxxxxxxxxx>
---
 drivers/net/dsa/lantiq/mxl-gsw1xx.c | 25 +++++++++++++++++++++++++
 drivers/net/dsa/lantiq/mxl-gsw1xx.h |  4 ++++
 2 files changed, 29 insertions(+)

diff --git a/drivers/net/dsa/lantiq/mxl-gsw1xx.c b/drivers/net/dsa/lantiq/mxl-gsw1xx.c
index a26f78e1a4..94a7eff5e0 100644
--- a/drivers/net/dsa/lantiq/mxl-gsw1xx.c
+++ b/drivers/net/dsa/lantiq/mxl-gsw1xx.c
@@ -18,6 +18,7 @@
 #include <linux/phy/phy-common-props.h>
 #include <linux/property.h>
 #include <linux/regmap.h>
+#include <linux/reset.h>
 #include <linux/workqueue.h>
 #include <net/dsa.h>
 
@@ -719,6 +720,7 @@ static int gsw1xx_serdes_pcs_init(struct gsw1xx_priv *priv)
 static int gsw1xx_probe(struct mdio_device *mdiodev)
 {
 	struct device *dev = &mdiodev->dev;
+	struct reset_control *reset;
 	struct gsw1xx_priv *priv;
 	u32 version, val;
 	u8 shellver;
@@ -737,6 +739,29 @@ static int gsw1xx_probe(struct mdio_device *mdiodev)
 	if (!priv->gswip.hw_info)
 		return -EINVAL;
 
+	/* The MDIO core handles reset-gpios only for PHYs. Reset the switch
+	 * here, so it does not run with whatever the bootloader configured.
+	 */
+	reset = devm_reset_control_get_optional_exclusive(dev, NULL);
+	if (IS_ERR(reset))
+		return dev_err_probe(dev, PTR_ERR(reset),
+				     "failed to get reset control\n");
+
+	if (reset) {
+		ret = reset_control_assert(reset);
+		if (ret)
+			return dev_err_probe(dev, ret, "failed to assert reset\n");
+
+		fsleep(GSW1XX_RESET_ASSERT_US);
+
+		ret = reset_control_deassert(reset);
+		if (ret)
+			return dev_err_probe(dev, ret,
+					     "failed to deassert reset\n");
+
+		fsleep(GSW1XX_RESET_DEASSERT_US);
+	}
+
 	priv->gswip.gswip = gsw1xx_regmap_init(priv, "switch",
 					       GSW1XX_SWITCH_BASE, 0xfff);
 	if (IS_ERR(priv->gswip.gswip))
diff --git a/drivers/net/dsa/lantiq/mxl-gsw1xx.h b/drivers/net/dsa/lantiq/mxl-gsw1xx.h
index 81bc00eabb..bca8e3223c 100644
--- a/drivers/net/dsa/lantiq/mxl-gsw1xx.h
+++ b/drivers/net/dsa/lantiq/mxl-gsw1xx.h
@@ -19,6 +19,10 @@
 
 #define GSW1XX_SYS_CLK_FREQ			340000000
 
+/* Hardware reset timing of the vendor's driver for the GSW150 */
+#define GSW1XX_RESET_ASSERT_US			250000
+#define GSW1XX_RESET_DEASSERT_US		1000000
+
 /* SMDIO switch register base address */
 #define GSW1XX_SMDIO_BADR			0x1f
 #define  GSW1XX_SMDIO_BADR_UNKNOWN		-1

-- 
Git-155)