[PATCH] clk: composite: Also consider .determine_rate for rate + mux composites

Martin Blumenstingl
2021-10-15T12:06:31Z

Commit 69a00fb3d69706 ("clk: divider: Implement and wire up
.determine_rate by default") switches clk_divider_ops to implement
.determine_rate by default. This breaks composite clocks with multiple
parents because clk-composite.c does not use the special handling for
mux + divider combinations anymore (that was restricted to rate clocks
which only implement .round_rate, but not .determine_rate).

Alex reports:
This breaks lot of clocks for Rockchip which intensively uses
composites, i.e. those clocks will always stay at the initial parent,
which in some cases is the XTAL clock and I strongly guess it is the
same for other platforms, which use composite clocks having more than
one parent (e.g. mediatek, ti ...)

Example (RK3399)
clk_sdio is set (initialized) with XTAL (24 MHz) as parent in u-boot.
It will always stay at this parent, even if the mmc driver sets a rate
of 200 MHz (fails, as the nature of things), which should switch it
to any of its possible parent PLLs defined in
mux_pll_src_cpll_gpll_npll_ppll_upll_24m_p (see clk-rk3399.c) - which
never happens.

Restore the original behavior by changing the priority of the conditions
inside clk-composite.c. Now the special rate + mux case (with rate_ops
having a .round_rate - which is still the case for the default
clk_divider_ops) is preferred over rate_ops which have .determine_rate
defined (and not further considering the mux).

Fixes: 69a00fb3d69706 ("clk: divider: Implement and wire up .determine_rate by default")
Reported-by: Alex Bee <knaerzche@gmail.com>
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
---
Re-sending this as inline patch instead of attaching it.

drivers/clk/clk-composite.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/clk/clk-composite.c b/drivers/clk/clk-composite.c
index 0506046a5f4b..510a9965633b 100644
--- a/drivers/clk/clk-composite.c
+++ b/drivers/clk/clk-composite.c
@@ -58,11 +58,8 @@ static int clk_composite_determine_rate(struct clk_hw *hw,
long rate;
int i;

- if (rate_hw && rate_ops && rate_ops->determine_rate) {
- __clk_hw_set_clk(rate_hw, hw);
- return rate_ops->determine_rate(rate_hw, req);
- } else if (rate_hw && rate_ops && rate_ops->round_rate &&
- mux_hw && mux_ops && mux_ops->set_parent) {
+ if (rate_hw && rate_ops && rate_ops->round_rate &&
+ mux_hw && mux_ops && mux_ops->set_parent) {
req->best_parent_hw = NULL;

if (clk_hw_get_flags(hw) & CLK_SET_RATE_NO_REPARENT) {
@@ -107,6 +104,9 @@ static int clk_composite_determine_rate(struct clk_hw *hw,

req->rate = best_rate;
return 0;
+ } else if (rate_hw && rate_ops && rate_ops->determine_rate) {
+ __clk_hw_set_clk(rate_hw, hw);
+ return rate_ops->determine_rate(rate_hw, req);
} else if (mux_hw && mux_ops && mux_ops->determine_rate) {
__clk_hw_set_clk(mux_hw, hw);
return mux_ops->determine_rate(mux_hw, req);
--
2.33.0