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: 620136c ("cpufreq/amd-pstate: Modularize perf<->freq conversion")
Signed-off-by: Dhananjay Ugwekar <[email protected]>
Reviewed-by: Mario Limonciello <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Mario Limonciello <[email protected]>

Author: dhananjay-AMD

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)