Re: [RFC] Allow for gate and mux control using non-atomic GPIO

[Jyri Sarha <jsarha@ti.com>]

I did not have time to give this a full review and test, but there is 
atleast one comment bellow.

Best regards,
Jyri

On 08/18/15 18:40, Michael Allwright wrote:
> Hi,
>
> The current implementation of clk-gpio completely ignores the use case
> where GPIO pins may be accessed over a message based bus like SPI or
> I2C. To fix this, and following the comments in clk.h, we shclk_gpio_gate_prepareould use
> the prepare/unprepare methods to do the work where the GPIO operation
> would be non-atomic. I propose the following UNTESTED patch (should
> apply cleanly over linux-next).
>
>  From 7a21c155e561d84741ce11f0cc4c1f8c5b97d7dc Mon Sep 17 00:00:00 2001clk_gpio_gate_prepare
> From: Michael Allwright <allsey87@gmail.com>
> Date: Tue, 18 Aug 2015 17:26:34 +0200
> Subject: [PATCH] Allow non-atomic GPIO ops to control gates and muxes.
>   Following the comments in clk.h, use prepare/unprepare methods to do the GPIO
>   work in cases where the specified pin can sleep
>
> ---
>   drivers/clk/clk-gpio.c | 50 ++++++++++++++++++++++++++++++++++++++++++++------
>   1 file changed, 44 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/clk/clk-gpio.c b/drivers/clk/clk-gpio.c
> index 10819e2..3172073 100644
> --- a/drivers/clk/clk-gpio.c
> +++ b/drivers/clk/clk-gpio.c
> @@ -56,6 +56,29 @@ static int clk_gpio_gate_is_enabled(struct clk_hw *hw)
>       return gpiod_get_value(clk->gpiod);
>   }
>
> +static int clk_gpio_gate_prepare(struct clk_hw *hw)
> +{
> +    struct clk_gpio *clk = to_clk_gpio(hw);
> +
> +    gpiod_set_value_cansleep(clk->gpiod, 1);
> +
> +    return 0;
> +}
> +
> +static void clk_gpio_gate_unprepare(struct clk_hw *hw)
> +{
> +    struct clk_gpio *clk = to_clk_gpio(hw);
> +clk_gpio_gate_prepare
> +    gpiod_set_value_cansleep(clk->gpiod, 0);
> +}
> +
> +static int clk_gpio_gate_is_prepared(struct clk_hw *hw)
> +{
> +    struct clk_gpio *clk = to_clk_gpio(hw);
> +
> +    return gpiod_get_value_cansleep(clk->gpiod);
> +}
> +
>   const struct clk_ops clk_gpio_gate_ops = {
>       .enable = clk_gpio_gate_enable,
>       .disable = clk_gpio_gate_disable,
> @@ -63,6 +86,14 @@ const struct clk_ops clk_gpio_gate_ops = {
>   };
>   EXPORT_SYMBOL_GPL(clk_gpio_gate_ops);
>
> +const struct clk_ops clk_sleepable_gpio_gate_ops = {
> +    .enable = clk_gpio_gate_prepare,
> +    .disable = clk_gpio_gate_unprepare,
> +    .is_enabled = clk_gpio_gate_is_prepared,
> +};
> +EXPORT_SYMBOL_GPL(clk_sleepable_gpio_gate_ops);

Shouldn't the .prepare .unprepare .is_prepared be assigned to *prepare() 
functions and leave .enable etc. as null?

Does this even work, doesn't the CCF complain about sleeping in 
.enable() etc. callbacks?

> +
> +
>   /**
>    * DOC: basic clock multiplexer which can be controlled with a gpio output
>    * Traits of this clock:
> @@ -75,14 +106,14 @@ static u8 clk_gpio_mux_get_parent(struct clk_hw *hw)
>   {
>       struct clk_gpio *clk = to_clk_gpio(hw);
>
> -    return gpiod_get_value(clk->gpiod);
> +    return gpiod_get_value_cansleep(clk->gpiod);
>   }
>
>   static int clk_gpio_mux_set_parent(struct clk_hw *hw, u8 index)
>   {
>       struct clk_gpio *clk = to_clk_gpio(hw);
>
> -    gpiod_set_value(clk->gpiod, index);
> +    gpiod_set_value_cansleep(clk->gpiod, index);
>
>       return 0;
>   }
> @@ -170,10 +201,17 @@ struct clk *clk_register_gpio_gate(struct device
> *dev, const char *name,
>           const char *parent_name, unsigned gpio, bool active_low,
>           unsigned long flags)
>   {
> -    return clk_register_gpio(dev, name,
> -            (parent_name ? &parent_name : NULL),
> -            (parent_name ? 1 : 0), gpio, active_low, flags,
> -            &clk_gpio_gate_ops);
> +    if(gpio_cansleep(gpio))
> +        return clk_register_gpio(dev, name,
> +                (parent_name ? &parent_name : NULL),
> +                (parent_name ? 1 : 0), gpio, active_low, flags,
> +                &clk_sleepable_gpio_gate_ops);
> +    else
> +        return clk_register_gpio(dev, name,
> +                (parent_name ? &parent_name : NULL),
> +                (parent_name ? 1 : 0), gpio, active_low, flags,
> +                &clk_gpio_gate_ops);
> +
>   }
>   EXPORT_SYMBOL_GPL(clk_register_gpio_gate);
>