linux-kernel - Re: [PATCH] mdio_bus: Issue GPIO RESET to PHYs.

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Message-ID: <f8624649-3e49-f68c-f364-ee73f1cc514d@ti.com>
Date:   Wed, 19 Apr 2017 14:56:48 +0300
From:   Roger Quadros <rogerq@...com>
To:     Andrew Lunn <andrew@...n.ch>
CC:     <davem@...emloft.net>, Florian Fainelli <f.fainelli@...il.com>,
        <tony@...mide.com>, <nsekhar@...com>, <jsarha@...com>,
        <netdev@...r.kernel.org>, <linux-omap@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mdio_bus: Issue GPIO RESET to PHYs.

Hi,

On 19/04/17 14:39, Andrew Lunn wrote:
> On Wed, Apr 19, 2017 at 12:24:26PM +0300, Roger Quadros wrote:
>> 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@...com>
>> ---
>>  drivers/net/phy/mdio_bus.c | 26 ++++++++++++++++++++++++++
>>  drivers/of/of_mdio.c       |  4 ++++
>>  include/linux/phy.h        |  5 +++++
>>  3 files changed, 35 insertions(+)
> 
> Hi Roger
> 
> Thanks for making this generic.
> 
> Please add device tree binding documentation. I think that actually
> means you have to document MDIO in general, since there currently is
> not a binding document.

OK.

> 
>> diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
>> index fa7d51f..25fda2b 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>
>> @@ -43,6 +46,8 @@
>>  
>>  #include "mdio-boardinfo.h"
>>  
>> +#define DEFAULT_GPIO_RESET_DELAY	10	/* in microseconds */
>> +
>>  int mdiobus_register_device(struct mdio_device *mdiodev)
>>  {
>>  	if (mdiodev->bus->mdio_map[mdiodev->addr])
>> @@ -307,6 +312,7 @@ 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 +339,26 @@ 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);
> 
> 
>> +			if (!bus->reset_delay_us)
>> +				bus->reset_delay_us = DEFAULT_GPIO_RESET_DELAY;
> 
> Maybe do this once, where you read the device tree property.

I was thinking from point of view that GPIO RESET code should work even without
device tree. Although I'm not sure if there would be any users or not.

> 
> 
>> +			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..83a62e4 100644
>> --- a/drivers/of/of_mdio.c
>> +++ b/drivers/of/of_mdio.c
>> @@ -221,6 +221,10 @@ int of_mdiobus_register(struct mii_bus *mdio, struct device_node *np)
>>  
>>  	mdio->dev.of_node = np;
>>  
>> +	/* Get bus level PHY reset GPIO details */
>> +	of_property_read_u32(np, "reset-delay-us", &mdio->reset_delay_us);
> 
> If the property does not exist, it is guaranteed mdio->reset_delay_us
> is not changed. So you can set it to the default value before, then do
> this call.
> 
>      Andrew
> 

cheers,
-roger