[AMD Official Use Only - AMD Internal Distribution Only]
> -----Original Message----- > From: Stephen Hemminger <[email protected]> > Sent: Sunday, March 29, 2026 1:04 AM > To: [email protected] > Cc: Stephen Hemminger <[email protected]>; [email protected]; > Anatoly Burakov <[email protected]>; Tummala, Sivaprasad > <[email protected]> > Subject: [PATCH] power/amd_pstate: fix frequency matching for continuous > scaling > > Caution: This message originated from an External Source. Use proper caution > when opening attachments, clicking links, or responding. > > > The power_init_for_setting_freq() function fails on systems using the > amd-pstate- > epp driver because the current CPU frequency read from scaling_setspeed does > not exactly match any of the synthesized frequency buckets. Unlike > acpi_cpufreq > which provides a discrete list of frequencies, amd-pstate operates with > continuously > variable frequencies, so an exact match will rarely succeed. > > For example, on a Ryzen 9 7945HX the sysfs file reports 2797172 which rounds > to > 2797000, but this value does not appear in the generated frequency table. > > Replace the exact match lookup with a nearest-frequency search. > > Also fix several issues in the same function: > - strtoul() was called with NULL endptr, making parse failures > undetectable > - errno was not checked, so stale errors could cause false positives > - freq was declared as uint32_t, truncating the unsigned long > return value of strtoul() on LP64 platforms > - no error was logged when frequency matching failed > > Bugzilla ID: 1915 > Fixes: 1ed04d33cf19 ("power: support amd-pstate cpufreq driver") > Cc: [email protected] > > Signed-off-by: Stephen Hemminger <[email protected]> > --- > drivers/power/amd_pstate/amd_pstate_cpufreq.c | 56 ++++++++++++++----- > 1 file changed, 41 insertions(+), 15 deletions(-) > > diff --git a/drivers/power/amd_pstate/amd_pstate_cpufreq.c > b/drivers/power/amd_pstate/amd_pstate_cpufreq.c > index 95495bff7d..14625ffd73 100644 > --- a/drivers/power/amd_pstate/amd_pstate_cpufreq.c > +++ b/drivers/power/amd_pstate/amd_pstate_cpufreq.c > @@ -5,6 +5,7 @@ > */ > > #include <stdlib.h> > +#include <errno.h> > > #include <rte_memcpy.h> > #include <rte_stdatomic.h> > @@ -291,15 +292,21 @@ power_get_available_freqs(struct > amd_pstate_power_info *pi) > return ret; > } > > -/** > - * It is to fopen the sys file for the future setting the lcore frequency. > - */ > +static inline unsigned long > +abs_diff(unsigned long a, unsigned long b) { > + return (a > b) ? a - b : b - a; > +} > + > static int > power_init_for_setting_freq(struct amd_pstate_power_info *pi) { > - FILE *f = NULL; > + FILE *f; > char buf[BUFSIZ]; > - uint32_t i, freq; > + char *endptr; > + unsigned long freq, freq_conv; > + unsigned long best_diff, diff; > + uint32_t i, best_idx; > int ret; > > open_core_sysfs_file(&f, "rw+", POWER_SYSFILE_SETSPEED, pi- > >lcore_id); @@ -308,7 +315,6 @@ power_init_for_setting_freq(struct > amd_pstate_power_info *pi) > POWER_SYSFILE_SETSPEED); > goto err; > } > - > ret = read_core_sysfs_s(f, buf, sizeof(buf)); > if (ret < 0) { > POWER_LOG(ERR, "Failed to read %s", @@ -316,25 +322,45 @@ > power_init_for_setting_freq(struct amd_pstate_power_info *pi) > goto err; > } > > - freq = strtoul(buf, NULL, POWER_CONVERT_TO_DECIMAL); > + errno = 0; > + freq = strtoul(buf, &endptr, POWER_CONVERT_TO_DECIMAL); > + if (errno != 0 || endptr == buf || freq == 0) { > + POWER_LOG(ERR, "Failed to parse frequency '%s' for lcore %u", > + buf, pi->lcore_id); > + goto err; > + } > > /* convert the frequency to nearest 1000 value > * Ex: if freq=1396789 then freq_conv=1397000 > * Ex: if freq=800030 then freq_conv=800000 > */ > - unsigned int freq_conv = 0; > - freq_conv = (freq + FREQ_ROUNDING_DELTA) > - / ROUND_FREQ_TO_N_1000; > + freq_conv = (freq + FREQ_ROUNDING_DELTA) / > ROUND_FREQ_TO_N_1000; > freq_conv = freq_conv * ROUND_FREQ_TO_N_1000; > > - for (i = 0; i < pi->nb_freqs; i++) { > - if (freq_conv == pi->freqs[i]) { > - pi->curr_idx = i; > - pi->f = f; > - return 0; > + /* Find the nearest frequency in the table. > + * With amd-pstate the CPU runs at continuously variable > + * frequencies so the current frequency will not exactly > + * match one of the synthesized frequency buckets. > + */ > + best_idx = 0; > + best_diff = abs_diff(freq_conv, pi->freqs[0]); > + > + for (i = 1; i < pi->nb_freqs; i++) { > + diff = abs_diff(freq_conv, pi->freqs[i]); > + if (diff < best_diff) { > + best_diff = diff; > + best_idx = i; > } > } > > + POWER_DEBUG_LOG("Freq %lu rounded to %lu matched bucket [%u] = > %u " > + "for lcore %u", freq, freq_conv, best_idx, > + pi->freqs[best_idx], pi->lcore_id); > + > + pi->curr_idx = best_idx; > + pi->f = f; > + return 0; > + > err: > if (f != NULL) > fclose(f); > -- > 2.53.0 LGTM Acked-by: Sivaprasad Tummala <[email protected]>
