power: check sysfs base frequency

Some kernels may show in incorrect value for base frequency in
sysfs (e.g. 15 GHz). This throws off the SST-BF algorithm for
high and low priority cores. So if base_frequency is greater
than max turbo frequency, ignore, and handle it as a normal
core.

Known Kernel version with issue: Linux 5.8.7

Signed-off-by: David Hunt <david.hunt@intel.com>

diff --git a/lib/librte_power/power_pstate_cpufreq.c b/lib/librte_power/power_pstate_cpufreq.c
index edf6328..8a1fffa 100644 (file)
--- a/lib/librte_power/power_pstate_cpufreq.c
+++ b/lib/librte_power/power_pstate_cpufreq.c
@@ -154,29 +154,49 @@ out:      close(fd);
 static int
 power_init_for_setting_freq(struct pstate_power_info *pi)
 {
-       FILE *f_min, *f_max, *f_base;
+       FILE *f_min, *f_max, *f_base = NULL, *f_base_max;
        char fullpath_min[PATH_MAX];
        char fullpath_max[PATH_MAX];
        char fullpath_base[PATH_MAX];
+       char fullpath_base_max[PATH_MAX];
        char buf_base[BUFSIZ];
        char *s_base;
+       char *s_base_max;
        uint32_t base_ratio = 0;
+       uint32_t base_max_ratio = 0;
        uint64_t max_non_turbo = 0;
        int  ret_val = 0;
 
-       snprintf(fullpath_min, sizeof(fullpath_min), POWER_SYSFILE_MIN_FREQ,
+       snprintf(fullpath_base_max,
+                       sizeof(fullpath_base_max),
+                       POWER_SYSFILE_BASE_MAX_FREQ,
                        pi->lcore_id);
+       f_base_max = fopen(fullpath_base_max, "r");
+       FOPEN_OR_ERR_RET(f_base_max, -1);
+       if (f_base_max != NULL) {
+               s_base_max = fgets(buf_base, sizeof(buf_base), f_base_max);
+               FOPS_OR_NULL_GOTO(s_base_max, out);
 
+               buf_base[BUFSIZ-1] = '\0';
+               if (strlen(buf_base))
+                       /* Strip off terminating '\n' */
+                       strtok(buf_base, "\n");
+
+               base_max_ratio =
+                       strtoul(buf_base, NULL, POWER_CONVERT_TO_DECIMAL)
+                               / BUS_FREQ;
+       }
+
+       snprintf(fullpath_min, sizeof(fullpath_min), POWER_SYSFILE_MIN_FREQ,
+                       pi->lcore_id);
        f_min = fopen(fullpath_min, "rw+");
        FOPEN_OR_ERR_RET(f_min, -1);
 
        snprintf(fullpath_max, sizeof(fullpath_max), POWER_SYSFILE_MAX_FREQ,
                        pi->lcore_id);
-
        f_max = fopen(fullpath_max, "rw+");
        if (f_max == NULL)
                fclose(f_min);
-
        FOPEN_OR_ERR_RET(f_max, -1);
 
        pi->f_cur_min = f_min;
@@ -186,6 +206,7 @@ power_init_for_setting_freq(struct pstate_power_info *pi)
                        pi->lcore_id);
 
        f_base = fopen(fullpath_base, "r");
+       FOPEN_OR_ERR_RET(f_base, -1);
        if (f_base == NULL) {
                /* No sysfs base_frequency, that's OK, continue without */
                base_ratio = 0;
@@ -215,6 +236,17 @@ power_init_for_setting_freq(struct pstate_power_info *pi)
 
        pi->non_turbo_max_ratio = max_non_turbo;
 
+       /*
+        * If base_frequency is reported as greater than the maximum
+        * turbo frequency, that's a known issue with some kernels.
+        * Set base_frequency to max_non_turbo as a workaround.
+        */
+       if (base_ratio > base_max_ratio) {
+               /* base_ratio is greater than max turbo. Kernel bug. */
+               pi->priority_core = 0;
+               goto out;
+       }
+
        /*
         * If base_frequency is reported as greater than the maximum
         * non-turbo frequency, then mark it as a high priority core.