On Fri, Oct 13, 2023 at 11:31:14AM +0800, Meng Li wrote:
> +#define AMD_PSTATE_PREFCORE_THRESHOLD 166
> +#define AMD_PSTATE_MAX_CPPC_PERF 255
> +static void amd_pstate_init_prefcore(struct amd_cpudata *cpudata)
> +{
> + int ret, prio;
> + u32 highest_perf;
> + static u32 max_highest_perf = 0, min_highest_perf = U32_MAX;
What serializes these things?
Also, *why* are you using u32 here, what's wrong with something like:
int max_hp = INT_MIN, min_hp = INT_MAX;
> +
> + ret = amd_pstate_get_highest_perf(cpudata->cpu, &highest_perf);
> + if (ret)
> + return;
> +
> + cpudata->hw_prefcore = true;
> + /* check if CPPC preferred core feature is enabled*/
> + if (highest_perf == AMD_PSTATE_MAX_CPPC_PERF) {
Which effectively means <255 (also, seems to suggest MAX_CPPC_PERF might
not be the best name, hmm?)
Should you not write '>= 255' then? Just in case something 'funny'
happens?
> + pr_debug("AMD CPPC preferred core is unsupported!\n");
> + cpudata->hw_prefcore = false;
> + return;
> + }
> +
> + if (!amd_pstate_prefcore)
> + return;
> +
> + /* The maximum value of highest perf is 255 */
> + prio = (int)(highest_perf & 0xff);
If for some weird reason you get 0x1ff or whatever above (dodgy BIOS
never happens, right) then this makes sense how?
Perhaps stop sending patches at break-nek speed and think for a little
while on how to write this and not be confused?
> + /*
> + * The priorities can be set regardless of whether or not
> + * sched_set_itmt_support(true) has been called and it is valid to
> + * update them at any time after it has been called.
> + */
> + sched_set_itmt_core_prio(prio, cpudata->cpu);
> +
> + if (max_highest_perf <= min_highest_perf) {
> + if (highest_perf > max_highest_perf)
> + max_highest_perf = highest_perf;
> +
> + if (highest_perf < min_highest_perf)
> + min_highest_perf = highest_perf;
> +
> + if (max_highest_perf > min_highest_perf) {
> + /*
> + * This code can be run during CPU online under the
> + * CPU hotplug locks, so sched_set_itmt_support()
> + * cannot be called from here. Queue up a work item
> + * to invoke it.
> + */
> + schedule_work(&sched_prefcore_work);
> + }
> + }
Not a word about what serializes these variables.
> +}
