Re: [PATCH v2 10/12] clk: sunxi: mod0: Introduce MMC proper phase handling

[Mike Turquette <mturquette@linaro.org>]

Quoting Maxime Ripard (2014-08-30 13:03:09)
> The MMC clock we thought we had until now are actually not one but three
> different clocks.
> 
> The main one is unchanged, and will have three outputs:
>   - The clock fed into the MMC
>   - a sample and output clocks, to deal with when should we output/sample data
>     to/from the MMC bus
> 
> The phase control we had are actually controlling the two latter clocks, but
> the main MMC one is unchanged.
> 
> We can adjust the phase with a 3 bits value, from 0 to 7, 0 meaning a 180 phase
> shift, and the other values being the number of periods from the MMC parent
> clock to outphase the clock of.
> 
> Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>

Looks good. Thanks a lot for revisiting this after talking to your
hardware team!

Regards,
Mike

> ---
>  Documentation/devicetree/bindings/clock/sunxi.txt |   2 +
>  drivers/clk/sunxi/clk-mod0.c                      | 189 ++++++++++++++++++++++
>  2 files changed, 191 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/clock/sunxi.txt b/Documentation/devicetree/bindings/clock/sunxi.txt
> index b938a990602a..eb690ed92a53 100644
> --- a/Documentation/devicetree/bindings/clock/sunxi.txt
> +++ b/Documentation/devicetree/bindings/clock/sunxi.txt
> @@ -47,6 +47,8 @@ Required properties:
>         "allwinner,sun6i-a31-apb2-gates-clk" - for the APB2 gates on A31
>         "allwinner,sun8i-a23-apb2-gates-clk" - for the APB2 gates on A23
>         "allwinner,sun5i-a13-mbus-clk" - for the MBUS clock on A13
> +       "allwinner,sun4i-a10-mmc-output-clk" - for the MMC output clock on A10
> +       "allwinner,sun4i-a10-mmc-sample-clk" - for the MMC sample clock on A10
>         "allwinner,sun4i-a10-mod0-clk" - for the module 0 family of clocks
>         "allwinner,sun7i-a20-out-clk" - for the external output clocks
>         "allwinner,sun7i-a20-gmac-clk" - for the GMAC clock module on A20/A31
> diff --git a/drivers/clk/sunxi/clk-mod0.c b/drivers/clk/sunxi/clk-mod0.c
> index 8a7f7036aea3..4a563850ee6e 100644
> --- a/drivers/clk/sunxi/clk-mod0.c
> +++ b/drivers/clk/sunxi/clk-mod0.c
> @@ -16,6 +16,7 @@
>  
>  #include <linux/clk-provider.h>
>  #include <linux/clkdev.h>
> +#include <linux/of_address.h>
>  
>  #include "clk-factors.h"
>  
> @@ -92,3 +93,191 @@ static void __init sun5i_a13_mbus_setup(struct device_node *node)
>         clk_prepare_enable(mbus);
>  }
>  CLK_OF_DECLARE(sun5i_a13_mbus, "allwinner,sun5i-a13-mbus-clk", sun5i_a13_mbus_setup);
> +
> +struct mmc_phase_data {
> +       u8      offset;
> +};
> +
> +struct mmc_phase {
> +       struct clk_hw           hw;
> +       void __iomem            *reg;
> +       struct mmc_phase_data   *data;
> +       spinlock_t              *lock;
> +};
> +
> +#define to_mmc_phase(_hw) container_of(_hw, struct mmc_phase, hw)
> +
> +static int mmc_get_phase(struct clk_hw *hw)
> +{
> +       struct clk *mmc, *mmc_parent, *clk = hw->clk;
> +       struct mmc_phase *phase = to_mmc_phase(hw);
> +       unsigned int mmc_rate, mmc_parent_rate;
> +       u16 step, mmc_div;
> +       u32 value;
> +       u8 delay;
> +
> +       value = readl(phase->reg);
> +       delay = (value >> phase->data->offset) & 0x3;
> +
> +       if (!delay)
> +               return 180;
> +
> +       /* Get the main MMC clock */
> +       mmc = clk_get_parent(clk);
> +       if (!mmc)
> +               return -EINVAL;
> +
> +       /* And its rate */
> +       mmc_rate = clk_get_rate(mmc);
> +       if (!mmc_rate)
> +               return -EINVAL;
> +
> +       /* Now, get the MMC parent (most likely some PLL) */
> +       mmc_parent = clk_get_parent(mmc);
> +       if (!mmc_parent)
> +               return -EINVAL;
> +
> +       /* And its rate */
> +       mmc_parent_rate = clk_get_rate(mmc_parent);
> +       if (!mmc_parent_rate)
> +               return -EINVAL;
> +
> +       /* Get MMC clock divider */
> +       mmc_div = mmc_parent_rate / mmc_rate;
> +
> +       step = DIV_ROUND_CLOSEST(360, mmc_div);
> +       return delay * step;
> +}
> +
> +static int mmc_set_phase(struct clk_hw *hw, int degrees)
> +{
> +       struct clk *mmc, *mmc_parent, *clk = hw->clk;
> +       struct mmc_phase *phase = to_mmc_phase(hw);
> +       unsigned int mmc_rate, mmc_parent_rate;
> +       unsigned long flags;
> +       u32 value;
> +       u8 delay;
> +
> +       /* Get the main MMC clock */
> +       mmc = clk_get_parent(clk);
> +       if (!mmc)
> +               return -EINVAL;
> +
> +       /* And its rate */
> +       mmc_rate = clk_get_rate(mmc);
> +       if (!mmc_rate)
> +               return -EINVAL;
> +
> +       /* Now, get the MMC parent (most likely some PLL) */
> +       mmc_parent = clk_get_parent(mmc);
> +       if (!mmc_parent)
> +               return -EINVAL;
> +
> +       /* And its rate */
> +       mmc_parent_rate = clk_get_rate(mmc_parent);
> +       if (!mmc_parent_rate)
> +               return -EINVAL;
> +
> +       if (degrees != 180) {
> +               u16 step, mmc_div;
> +
> +               /* Get MMC clock divider */
> +               mmc_div = mmc_parent_rate / mmc_rate;
> +
> +               /*
> +                * We can only outphase the clocks by multiple of the
> +                * PLL's period.
> +                *
> +                * Since the MMC clock in only a divider, and the
> +                * formula to get the outphasing in degrees is deg =
> +                * 360 * delta / period
> +                *
> +                * If we simplify this formula, we can see that the
> +                * only thing that we're concerned about is the number
> +                * of period we want to outphase our clock from, and
> +                * the divider set by the MMC clock.
> +                */
> +               step = DIV_ROUND_CLOSEST(360, mmc_div);
> +               delay = DIV_ROUND_CLOSEST(degrees, step);
> +       } else {
> +               delay = 0;
> +       }
> +
> +       spin_lock_irqsave(phase->lock, flags);
> +       value = readl(phase->reg);
> +       value &= ~GENMASK(phase->data->offset + 3, phase->data->offset);
> +       value |= delay << phase->data->offset;
> +       writel(value, phase->reg);
> +       spin_unlock_irqrestore(phase->lock, flags);
> +
> +       return 0;
> +}
> +
> +static const struct clk_ops mmc_clk_ops = {
> +       .get_phase      = mmc_get_phase,
> +       .set_phase      = mmc_set_phase,
> +};
> +
> +static void __init sun4i_a10_mmc_phase_setup(struct device_node *node,
> +                                            struct mmc_phase_data *data)
> +{
> +       const char *parent_names[1] = { of_clk_get_parent_name(node, 0) };
> +       struct clk_init_data init = {
> +               .num_parents    = 1,
> +               .parent_names   = parent_names,
> +               .ops            = &mmc_clk_ops,
> +       };
> +
> +       struct mmc_phase *phase;
> +       struct clk *clk;
> +
> +       phase = kmalloc(sizeof(*phase), GFP_KERNEL);
> +       if (!phase)
> +               return;
> +
> +       phase->hw.init = &init;
> +
> +       phase->reg = of_iomap(node, 0);
> +       if (!phase->reg)
> +               goto err_free;
> +
> +       phase->data = data;
> +       phase->lock = &sun4i_a10_mod0_lock;
> +
> +       if (of_property_read_string(node, "clock-output-names", &init.name))
> +               init.name = node->name;
> +
> +       clk = clk_register(NULL, &phase->hw);
> +       if (IS_ERR(clk))
> +               goto err_unmap;
> +
> +       of_clk_add_provider(node, of_clk_src_simple_get, clk);
> +
> +       return;
> +
> +err_unmap:
> +       iounmap(phase->reg);
> +err_free:
> +       kfree(phase);
> +}
> +
> +
> +static struct mmc_phase_data mmc_output_clk = {
> +       .offset = 8,
> +};
> +
> +static struct mmc_phase_data mmc_sample_clk = {
> +       .offset = 20,
> +};
> +
> +static void __init sun4i_a10_mmc_output_setup(struct device_node *node)
> +{
> +       sun4i_a10_mmc_phase_setup(node, &mmc_output_clk);
> +}
> +CLK_OF_DECLARE(sun4i_a10_mmc_output, "allwinner,sun4i-a10-mmc-output-clk", sun4i_a10_mmc_output_setup);
> +
> +static void __init sun4i_a10_mmc_sample_setup(struct device_node *node)
> +{
> +       sun4i_a10_mmc_phase_setup(node, &mmc_sample_clk);
> +}
> +CLK_OF_DECLARE(sun4i_a10_mmc_sample, "allwinner,sun4i-a10-mmc-sample-clk", sun4i_a10_mmc_sample_setup);
> -- 
> 2.0.2
>