[PATCH] clk: divider: support read-only dividers

[Michael Turquette]

An arbitrary clock rate divider may be set out of reset, or perhaps by
the bootloader or something other than Linux. In these cases we may want
to know the frequency of the clock signal, but we do not want to allow
Linux to change it.

The CLK_DIVIDER_READ_ONLY flag was intended to express this, but the
functionality was missing in the code. Add read-only clk_ops for divider
clocks to handle this case.

For hardware with fixed dividers it is still best to use the
fixed-factor clock type.

Reported-by: Joonyoung Shim <jy0922.shim@xxxxxxxxxxx>
Signed-off-by: Michael Turquette <mturquette@xxxxxxxxxx>
---
 drivers/clk/clk-divider.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/clk/clk-divider.c b/drivers/clk/clk-divider.c
index 25006a8..5d2de26 100644
--- a/drivers/clk/clk-divider.c
+++ b/drivers/clk/clk-divider.c
@@ -412,6 +412,11 @@ const struct clk_ops clk_divider_ops = {
 };
 EXPORT_SYMBOL_GPL(clk_divider_ops);
 
+const struct clk_ops clk_divider_ro_ops = {
+	.recalc_rate = clk_divider_recalc_rate,
+};
+EXPORT_SYMBOL_GPL(clk_divider_ro_ops);
+
 static struct clk *_register_divider(struct device *dev, const char *name,
 		const char *parent_name, unsigned long flags,
 		void __iomem *reg, u8 shift, u8 width,
@@ -437,7 +442,10 @@ static struct clk *_register_divider(struct device *dev, const char *name,
 	}
 
 	init.name = name;
-	init.ops = &clk_divider_ops;
+	if (clk_divider_flags & CLK_DIVIDER_READ_ONLY)
+		init.ops = &clk_divider_ro_ops;
+	else
+		init.ops = &clk_divider_ops;
 	init.flags = flags | CLK_IS_BASIC;
 	init.parent_names = (parent_name ? &parent_name: NULL);
 	init.num_parents = (parent_name ? 1 : 0);
-- 
1.9.1

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