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mdio_bus: Issue GPIO RESET to PHYs.

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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 <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
This commit is contained in:
Roger Quadros 2017-04-21 16:15:38 +03:00 • committed by David S. Miller
commit 69226896ad
4 changed files with 94 additions and 0 deletions
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7
drivers/of/of_mdio.c
View file

@ -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 <[email protected]>");
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)