Hi,
On 08/30/2014 10:03 PM, Maxime Ripard wrote:
> The current phase API doesn't look into the actual hardware to get the phase
> value, but will rather get it from a variable only set by the set_phase
> function.
>
> This will cause issue when the client driver will never call the set_phase
> function, where we can end up having a reported phase that will not match what
> the hardware has been programmed to by the bootloader or what phase is
> programmed out of reset.
>
> Add a new get_phase function for the drivers to implement so that we can get
> this value.
>
> Signed-off-by: Maxime Ripard <maxime.ripard@xxxxxxxxxxxxxxxxxx>
> ---
> drivers/clk/clk.c | 17 ++++++++++++++---
> include/linux/clk-provider.h | 5 +++++
> 2 files changed, 19 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index d87661af0c72..7dbceca694f1 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -1797,8 +1797,8 @@ out:
> * clk_get_phase - return the phase shift of a clock signal
> * @clk: clock signal source
> *
> - * Returns the phase shift of a clock node in degrees, otherwise returns
> - * -EERROR.
> + * Returns the phase shift of a clock node in degrees. Any negative
> + * values are errors.
> */
> int clk_get_phase(struct clk *clk)
> {
> @@ -1808,7 +1808,18 @@ int clk_get_phase(struct clk *clk)
> goto out;
>
> clk_prepare_lock();
> - ret = clk->phase;
> +
> + if (clk->phase) {
> + ret = clk->phase;
> + goto out_unlock;
> + }
0 is a valid phase, so this will cause the phase to
be read from the hardware each time if the phase is 0.
Perhaps make clk->phase signed (if it is not already), init it
to -1, and check for it not being -1 ?
Regards,
Hans
> +
> + if (!clk->ops->get_phase)
> + goto out_unlock;
> +
> + ret = clk->ops->get_phase(clk->hw);
> +
> +out_unlock:
> clk_prepare_unlock();
>
> out:
> diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
> index 69b20d4c1e1a..abec961092a7 100644
> --- a/include/linux/clk-provider.h
> +++ b/include/linux/clk-provider.h
> @@ -130,6 +130,10 @@ struct dentry;
> * set then clock accuracy will be initialized to parent accuracy
> * or 0 (perfect clock) if clock has no parent.
> *
> + * @get_phase: Queries the hardware to get the current phase of a clock.
> + * Returned values are 0-359 degrees on success, negative
> + * error codes on failure.
> + *
> * @set_phase: Shift the phase this clock signal in degrees specified
> * by the second argument. Valid values for degrees are
> * 0-359. Return 0 on success, otherwise -EERROR.
> @@ -182,6 +186,7 @@ struct clk_ops {
> unsigned long parent_rate, u8 index);
> unsigned long (*recalc_accuracy)(struct clk_hw *hw,
> unsigned long parent_accuracy);
> + int (*get_phase)(struct clk_hw *hw);
> int (*set_phase)(struct clk_hw *hw, int degrees);
> void (*init)(struct clk_hw *hw);
> int (*debug_init)(struct clk_hw *hw, struct dentry *dentry);
>
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