clk_mux: Fix set_parent doing the wrong thing when INDEX_BIT && index >= 3

If CLK_MUX_INDEX_BIT is set, then each bit turns on / off a single parent,
so theoretically multiple parents could be enabled at the same time, but in
practice only one bit should ever be 1. So to select parent 0, set
the register (*) to 0x01, to select parent 1 set it 0x02, parent 2, 0x04,
parent 3, 0x08, etc.

But the current code does:

                if (mux->flags & CLK_MUX_INDEX_BIT)
                        index = (1 << ffs(index));

Which means that:

For an input index of 0, ffs returns 0, so we set the register
to 0x01, ok.

For an input index of 1, ffs returns 1, so we set the register
to 0x02, ok.

For an input index of 2, ffs returns 2, so we set the register
to 0x04, ok.

For an input index of 3, ffs returns 1, so we set the register
to 0x02, not good!

The code should simply be:

                if (mux->flags & CLK_MUX_INDEX_BIT)
                        index = 1 << index;

Which always does the right thing, this commit fixes this.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Michael Turquette <mturquette@linaro.org>

diff --git a/drivers/clk/clk-mux.c b/drivers/clk/clk-mux.c
index 4f96ff3ba728321563cbdc6b728f9a25c65d74c6..6e1ecf94bf58daa279cb47e42065da9a9db3c581 100644 (file)
--- a/drivers/clk/clk-mux.c
+++ b/drivers/clk/clk-mux.c
@@ -77,7 +77,7 @@ static int clk_mux_set_parent(struct clk_hw *hw, u8 index)
 
        else {
                if (mux->flags & CLK_MUX_INDEX_BIT)
-                       index = (1 << ffs(index));
+                       index = 1 << index;
 
                if (mux->flags & CLK_MUX_INDEX_ONE)
                        index++;