[PATCH v3 1/2] clk: use ULONG_MAX as the initial value for the iteration in clk_mux_determine_rate_flags()

Yang Xiwen via B4 Relay
2023-04-26T19:34:25Z

From: Yang Xiwen <forbidden405@outlook.com>

Currently, clk_mux_determine_rate_flags() use 0 as the initial value for
selecting the best matching parent. However, this will choose a
non-existant rate(0) if the requested rate is closer to 0 than the
minimum rate the parents have.

Fix that by initializing the initial value to ULONG_MAX and treat it as a
magic number.

Signed-off-by: Yang Xiwen <forbidden405@outlook.com>
---
drivers/clk/clk.c | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index ae07685c7588b..6184d4aa88193 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -541,6 +541,17 @@ EXPORT_SYMBOL_GPL(__clk_is_enabled);
static bool mux_is_better_rate(unsigned long rate, unsigned long now,
unsigned long best, unsigned long flags)
{
+ if (rate == ULONG_MAX) {
+ // select the highest clock rate
+ if (best == ULONG_MAX)
+ return true;
+ else
+ return now > best;
+ }
+
+ if (best == ULONG_MAX && now <= rate)
+ return true;
+
if (flags & CLK_MUX_ROUND_CLOSEST)
return abs(now - rate) < abs(best - rate);

@@ -600,7 +611,7 @@ int clk_mux_determine_rate_flags(struct clk_hw *hw,
{
struct clk_core *core = hw->core, *parent, *best_parent = NULL;
int i, num_parents, ret;
- unsigned long best = 0;
+ unsigned long best = ULONG_MAX;

/* if NO_REPARENT flag set, pass through to current parent */
if (core->flags & CLK_SET_RATE_NO_REPARENT) {

--
2.39.2