cpufreq/amd-pstate: Fix the clamping of perf values

The clamping in freq_to_perf() is broken right now, as we first typecast
(read wraparound) the overflowing value into a u8 and then clamp it down.
So, use a u32 to store the >255 value in certain edge cases and then clamp
it down into a u8.

Also, use a "explicit typecast + clamp" instead of just a "clamp_t" as the
latter typecasts first and then clamps between the limits, which defeats
our purpose.

Fixes: 620136ced35a ("cpufreq/amd-pstate: Modularize perf<->freq conversion")
Signed-off-by: Dhananjay Ugwekar <dhananjay.ugwekar@amd.com>
Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
Link: https://lore.kernel.org/r/20250222033221.554976-1-dhananjay.ugwekar@amd.com
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>

diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index 08ae480768120acac14fc2ed22aef1890cf29d45..56930424c9fad51c2c5e20b82d4cae2f7a3c4169 100644 (file)
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -144,10 +144,10 @@ static struct quirk_entry quirk_amd_7k62 = {
 
 static inline u8 freq_to_perf(struct amd_cpudata *cpudata, unsigned int freq_val)
 {
-       u8 perf_val = DIV_ROUND_UP_ULL((u64)freq_val * cpudata->nominal_perf,
+       u32 perf_val = DIV_ROUND_UP_ULL((u64)freq_val * cpudata->nominal_perf,
                                        cpudata->nominal_freq);
 
-       return clamp_t(u8, perf_val, cpudata->lowest_perf, cpudata->highest_perf);
+       return (u8)clamp(perf_val, cpudata->lowest_perf, cpudata->highest_perf);
 }
 
 static inline u32 perf_to_freq(struct amd_cpudata *cpudata, u8 perf_val)