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Subject[PATCH v2] mdio_bus: Issue GPIO RESET to PHYs.
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Date
Some boards [1] leave the PHYs at an invalid state
during system power-up or reset thus causing unreliability
issues with the PHY which manifests as PHY not being detected
or link not functional. To fix this, these PHYs need to be RESET
via a GPIO connected to the PHY's RESET pin.

Some boards have a single GPIO controlling the PHY RESET pin of all
PHYs on the bus whereas some others have separate GPIOs controlling
individual PHY RESETs.

In both cases, the RESET de-assertion cannot be done in the PHY driver
as the PHY will not probe till its reset is de-asserted.
So do the RESET de-assertion in the MDIO bus driver.

[1] - am572x-idk, am571x-idk, a437x-idk

Signed-off-by: Roger Quadros <rogerq@ti.com>
---
v2:
- add device tree binding document (mdio.txt)
- specify default reset delay in of_mdio.c instead of mdio_bus.c

Documentation/devicetree/bindings/net/mdio.txt | 20 ++++++++++++++++++++
drivers/net/phy/mdio_bus.c | 22 ++++++++++++++++++++++
drivers/of/of_mdio.c | 7 +++++++
include/linux/phy.h | 5 +++++
4 files changed, 54 insertions(+)
create mode 100644 Documentation/devicetree/bindings/net/mdio.txt

diff --git a/Documentation/devicetree/bindings/net/mdio.txt b/Documentation/devicetree/bindings/net/mdio.txt
new file mode 100644
index 0000000..6e703d7
--- /dev/null
+++ b/Documentation/devicetree/bindings/net/mdio.txt
@@ -0,0 +1,20 @@
+Common MDIO bus properties.
+
+These are generic properties that can apply to any MDIO bus.
+
+Optional properties:
+- reset-gpios: List of one or more GPIOs that control the RESET lines
+ of the PHYs on that MDIO bus.
+- reset-delay-us: RESET pulse width as per PHY datasheet.
+
+Example :
+
+ davinci_mdio: ethernet@0x5c030000 {
+ compatible = "ti,davinci_mdio";
+ ti,hwmods = "davinci_mdio";
+ reg = <0x5c030000 0x1000>;
+ #address-cells = <1>;
+ #size-cells = <0>;
+ reset-gpios = <&gpio2 5 GPIO_ACTIVE_LOW>;
+ reset-delay-us = <2>; /* PHY datasheet states 1uS min */
+ };
diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
index fa7d51f..b353d99 100644
--- a/drivers/net/phy/mdio_bus.c
+++ b/drivers/net/phy/mdio_bus.c
@@ -22,8 +22,11 @@
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/device.h>
+#include <linux/gpio.h>
+#include <linux/gpio/consumer.h>
#include <linux/of_device.h>
#include <linux/of_mdio.h>
+#include <linux/of_gpio.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/skbuff.h>
@@ -307,6 +310,7 @@ int __mdiobus_register(struct mii_bus *bus, struct module *owner)
{
struct mdio_device *mdiodev;
int i, err;
+ struct gpio_desc *gpiod;

if (NULL == bus || NULL == bus->name ||
NULL == bus->read || NULL == bus->write)
@@ -333,6 +337,24 @@ int __mdiobus_register(struct mii_bus *bus, struct module *owner)
if (bus->reset)
bus->reset(bus);

+ /* de-assert bus level PHY GPIO resets */
+ for (i = 0; i < bus->num_reset_gpios; i++) {
+ gpiod = devm_gpiod_get_index(&bus->dev, "reset", i,
+ GPIOD_OUT_LOW);
+ if (IS_ERR(gpiod)) {
+ err = PTR_ERR(gpiod);
+ if (err != -ENOENT) {
+ pr_err("mii_bus %s couldn't get reset GPIO\n",
+ bus->id);
+ return err;
+ }
+ } else {
+ gpiod_set_value_cansleep(gpiod, 1);
+ udelay(bus->reset_delay_us);
+ gpiod_set_value_cansleep(gpiod, 0);
+ }
+ }
+
for (i = 0; i < PHY_MAX_ADDR; i++) {
if ((bus->phy_mask & (1 << i)) == 0) {
struct phy_device *phydev;
diff --git a/drivers/of/of_mdio.c b/drivers/of/of_mdio.c
index 0b29798..7e4c80f 100644
--- a/drivers/of/of_mdio.c
+++ b/drivers/of/of_mdio.c
@@ -22,6 +22,8 @@
#include <linux/of_net.h>
#include <linux/module.h>

+#define DEFAULT_GPIO_RESET_DELAY 10 /* in microseconds */
+
MODULE_AUTHOR("Grant Likely <grant.likely@secretlab.ca>");
MODULE_LICENSE("GPL");

@@ -221,6 +223,11 @@ int of_mdiobus_register(struct mii_bus *mdio, struct device_node *np)

mdio->dev.of_node = np;

+ /* Get bus level PHY reset GPIO details */
+ mdio->reset_delay_us = DEFAULT_GPIO_RESET_DELAY;
+ of_property_read_u32(np, "reset-delay-us", &mdio->reset_delay_us);
+ mdio->num_reset_gpios = of_gpio_named_count(np, "reset-gpios");
+
/* Register the MDIO bus */
rc = mdiobus_register(mdio);
if (rc)
diff --git a/include/linux/phy.h b/include/linux/phy.h
index 43a7748..80a6574 100644
--- a/include/linux/phy.h
+++ b/include/linux/phy.h
@@ -217,6 +217,11 @@ struct mii_bus {
* matching its address
*/
int irq[PHY_MAX_ADDR];
+
+ /* GPIO reset pulse width in uS */
+ int reset_delay_us;
+ /* Number of reset GPIOs */
+ int num_reset_gpios;
};
#define to_mii_bus(d) container_of(d, struct mii_bus, dev)

--
2.7.4

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