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SubjectRe: [PATCH 1/4] clk: propagate parent change up one level
Hi,

On 04.04.2014 16:53, Tomasz Stanislawski wrote:
> This patch adds support for propagation of setup of clock's parent one level
> up.
>
> This feature is helpful when a driver changes topology of its clocks using
> clk_set_parent(). The problem occurs when on one platform/SoC driver's clock
> is located at MUX output but on the other platform/SoC there is a gated proxy
> clock between the MUX and driver's clock. In such a case, driver's code has to
> be modified to use one clock for enabling and the other clock for setup of a
> parent.
>
> The code updates are avoided by propagating setup of a parent up one level.
>
> Additionally, this patch adds CLK_SET_PARENT_PARENT (sorry for naming) flag to
> inform clk-core that clk_set_parent() should be propagated.
>
> Signed-off-by: Tomasz Stanislawski <t.stanislaws@samsung.com>
> ---
> drivers/clk/clk.c | 6 ++++++
> include/linux/clk-provider.h | 1 +
> 2 files changed, 7 insertions(+)
>
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index dff0373..53bbfda 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -1737,6 +1737,12 @@ int clk_set_parent(struct clk *clk, struct clk *parent)
>
> /* try finding the new parent index */
> if (parent) {
> + if ((clk->flags & CLK_SET_PARENT_PARENT)
> + && clk->num_parents == 1) {
> + ret = clk_set_parent(clk->parent, parent);
> + goto out;
> + }
> +
> p_index = clk_fetch_parent_index(clk, parent);
> p_rate = parent->rate;
> if (p_index < 0) {
> diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
> index 5119174..daa0b03 100644
> --- a/include/linux/clk-provider.h
> +++ b/include/linux/clk-provider.h
> @@ -30,6 +30,7 @@
> #define CLK_GET_RATE_NOCACHE BIT(6) /* do not use the cached clk rate */
> #define CLK_SET_RATE_NO_REPARENT BIT(7) /* don't re-parent on rate change */
> #define CLK_GET_ACCURACY_NOCACHE BIT(8) /* do not use the cached clk accuracy */
> +#define CLK_SET_PARENT_PARENT BIT(9) /* propagate parent change up one level */
>
> struct clk_hw;
> struct dentry;
>

This would be very useful, at least on Exynos platforms, with
mux-div-gate clock paths. PARENT_PARENT sounds a bit funny, though.

Reviewed-by: Tomasz Figa <t.figa@samsung.com>

Best regards,
Tomasz


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