Re: [PATCH 1/4] clk: propagate parent change up one level

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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@xxxxxxxxxxx>
---
  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@xxxxxxxxxxx>

Best regards,
Tomasz
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