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Date:   Wed, 13 Feb 2019 09:14:22 -0800
From:   Stephen Boyd <sboyd@...nel.org>
To:     Michael Turquette <mturquette@...libre.com>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Cc:     linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH] clk: clk-gpio: add support for sleeping GPIOs in gpio-gate-clk

Quoting Thomas Petazzoni (2019-02-11 05:58:18)
> The current implementation of gpio-gate-clk enables/disables the clock
> using the GPIO in the ->enable() and ->disable() clock callbacks. This
> requires the GPIO to be configurable in atomic contexts. While it is
> the case for most memory-mapped GPIO controllers, it is not the case
> for GPIO expanders on I2C or SPI.
> 
> This commit extends the gpio-gate-clk to check whether the GPIO calls
> require sleeping or not. If sleeping is not required, the current
> implementation based on ->enable()/->disable() is kept. However, if
> sleeping is needed, we instead implement the logic in the ->prepare()
> and ->unprepare() hooks. Thanks to this, a gate clock connected to a
> GPIO on a GPIO expander can be controlled with the existing driver.
> 
> Signed-off-by: Thomas Petazzoni <thomas.petazzoni@...tlin.com>

Sounds like a good idea!

> diff --git a/drivers/clk/clk-gpio.c b/drivers/clk/clk-gpio.c
> index 6a43ce420492..f5d481713c7d 100644
> --- a/drivers/clk/clk-gpio.c
> +++ b/drivers/clk/clk-gpio.c
> @@ -61,6 +61,35 @@ const struct clk_ops clk_gpio_gate_ops = {
>  };
>  EXPORT_SYMBOL_GPL(clk_gpio_gate_ops);
>  
> +static int clk_sleeping_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_sleeping_gpio_gate_unprepare(struct clk_hw *hw)
> +{
> +       struct clk_gpio *clk = to_clk_gpio(hw);
> +
> +       gpiod_set_value_cansleep(clk->gpiod, 0);
> +}
> +
> +static int clk_sleeping_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_sleeping_gpio_gate_ops = {

static?

> +       .prepare = clk_sleeping_gpio_gate_prepare,
> +       .unprepare = clk_sleeping_gpio_gate_unprepare,
> +       .is_prepared = clk_sleeping_gpio_gate_is_prepared,
> +};
> +
>  /**
>   * DOC: basic clock multiplexer which can be controlled with a gpio output
>   * Traits of this clock:

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