linux-kernel - Re: [PATCH] net: davinci_mdio: add GPIO reset logic

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Message-ID: <20170405150334.GI13449@lunn.ch>
Date:   Wed, 5 Apr 2017 17:03:34 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Roger Quadros <rogerq@...com>
Cc:     davem@...emloft.net, tony@...mide.com, nsekhar@...com,
        jsarha@...com, netdev@...r.kernel.org, linux-omap@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: davinci_mdio: add GPIO reset logic

On Wed, Apr 05, 2017 at 11:33:57AM +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 like not being detected by the mdio bus
> or link not functional. To work around these boards have
> a GPIO connected to the PHY's reset pin.
> 
> Implement GPIO reset handling for such cases.
> 
> [1] - am572x-idk, am571x-idk, a437x-idk.
> 
> Signed-off-by: Roger Quadros <rogerq@...com>
> Signed-off-by: Sekhar Nori <nsekhar@...com>
> ---
>  .../devicetree/bindings/net/davinci-mdio.txt       |  2 +
>  drivers/net/ethernet/ti/davinci_mdio.c             | 68 +++++++++++++++++++---
>  2 files changed, 62 insertions(+), 8 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/net/davinci-mdio.txt b/Documentation/devicetree/bindings/net/davinci-mdio.txt
> index 621156c..fd6ebe7 100644
> --- a/Documentation/devicetree/bindings/net/davinci-mdio.txt
> +++ b/Documentation/devicetree/bindings/net/davinci-mdio.txt
> @@ -12,6 +12,8 @@ Required properties:
>  
>  Optional properties:
>  - ti,hwmods		: Must be "davinci_mdio"
> +- reset-gpios		: array of GPIO specifier for PHY hardware reset control
> +- reset-delay-us	: reset assertion time [in microseconds]
>  
>  Note: "ti,hwmods" field is used to fetch the base address and irq
>  resources from TI, omap hwmod data base during device registration.
> diff --git a/drivers/net/ethernet/ti/davinci_mdio.c b/drivers/net/ethernet/ti/davinci_mdio.c
> index 33df340..c6f9e55 100644
> --- a/drivers/net/ethernet/ti/davinci_mdio.c
> +++ b/drivers/net/ethernet/ti/davinci_mdio.c
> @@ -40,6 +40,9 @@
>  #include <linux/of_device.h>
>  #include <linux/of_mdio.h>
>  #include <linux/pinctrl/consumer.h>
> +#include <linux/gpio.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/of_gpio.h>
>  
>  /*
>   * This timeout definition is a worst-case ultra defensive measure against
> @@ -53,6 +56,8 @@
>  
>  #define DEF_OUT_FREQ		2200000		/* 2.2 MHz */
>  
> +#define DEFAULT_GPIO_RESET_DELAY	10	/* in microseconds */
> +
>  struct davinci_mdio_of_param {
>  	int autosuspend_delay_ms;
>  };
> @@ -104,6 +109,9 @@ struct davinci_mdio_data {
>  	 */
>  	bool		skip_scan;
>  	u32		clk_div;
> +	struct gpio_desc **gpio_reset;
> +	int		num_gpios;
> +	int		reset_delay_us;
>  };
>  
>  static void davinci_mdio_init_clk(struct davinci_mdio_data *data)
> @@ -142,6 +150,20 @@ static void davinci_mdio_enable(struct davinci_mdio_data *data)
>  	__raw_writel(data->clk_div | CONTROL_ENABLE, &data->regs->control);
>  }
>  
> +static void __davinci_gpio_reset(struct davinci_mdio_data *data)
> +{
> +	int i;
> +
> +	for (i = 0; i < data->num_gpios; i++) {
> +		if (!data->gpio_reset[i])
> +			continue;
> +
> +		gpiod_set_value_cansleep(data->gpio_reset[i], 1);
> +		udelay(data->reset_delay_us);
> +		gpiod_set_value_cansleep(data->gpio_reset[i], 0);
> +	}
> +}

Do you really need more than one GPIO? A single gpio would make all
this code a lot simpler.

     Andrew