Commit c4719563 authored by Jie Zhan's avatar Jie Zhan Committed by Viresh Kumar
Browse files

cppc_cpufreq: Use desired perf if feedback ctrs are 0 or unchanged 



The CPPC performance feedback counters could be 0 or unchanged when the
target cpu is in a low-power idle state, e.g. power-gated or clock-gated.

When the counters are 0, cppc_cpufreq_get_rate() returns 0 KHz, which makes
cpufreq_online() get a false error and fail to generate a cpufreq policy.

When the counters are unchanged, the existing cppc_perf_from_fbctrs()
returns a cached desired perf, but some platforms may update the real
frequency back to the desired perf reg.

For the above cases in cppc_cpufreq_get_rate(), get the latest desired perf
from the CPPC reg to reflect the frequency because some platforms may
update the actual frequency back there; if failed, use the cached desired
perf.

Fixes: 6a4fec4f ("cpufreq: cppc: cppc_cpufreq_get_rate() returns zero in all error cases.")
Signed-off-by: default avatarJie Zhan <zhanjie9@hisilicon.com>
Reviewed-by: default avatarZeng Heng <zengheng4@huawei.com>
Reviewed-by: default avatarIonela Voinescu <ionela.voinescu@arm.com>
Reviewed-by: default avatarHuisong Li <lihuisong@huawei.com>
Signed-off-by: default avatarViresh Kumar <viresh.kumar@linaro.org>
parent dfb6e2f5

drivers/cpufreq/cppc_cpufreq.c

+46 −11
Original line number Diff line number Diff line
@@ -118,6 +118,9 @@ static void cppc_scale_freq_workfn(struct kthread_work *work) 


	perf = cppc_perf_from_fbctrs(cpu_data, &cppc_fi->prev_perf_fb_ctrs,

				     &fb_ctrs);

	if (!perf)

		return;



	cppc_fi->prev_perf_fb_ctrs = fb_ctrs;



	perf <<= SCHED_CAPACITY_SHIFT;
@@ -724,13 +727,31 @@ static int cppc_perf_from_fbctrs(struct cppc_cpudata *cpu_data, 
	delta_delivered = get_delta(fb_ctrs_t1->delivered,

				    fb_ctrs_t0->delivered);



	/* Check to avoid divide-by zero and invalid delivered_perf */

	/*

	 * Avoid divide-by zero and unchanged feedback counters.

	 * Leave it for callers to handle.

	 */

	if (!delta_reference || !delta_delivered)

		return cpu_data->perf_ctrls.desired_perf;

		return 0;



	return (reference_perf * delta_delivered) / delta_reference;

}



static int cppc_get_perf_ctrs_sample(int cpu,

				     struct cppc_perf_fb_ctrs *fb_ctrs_t0,

				     struct cppc_perf_fb_ctrs *fb_ctrs_t1)

{

	int ret;



	ret = cppc_get_perf_ctrs(cpu, fb_ctrs_t0);

	if (ret)

		return ret;



	udelay(2); /* 2usec delay between sampling */



	return cppc_get_perf_ctrs(cpu, fb_ctrs_t1);

}



static unsigned int cppc_cpufreq_get_rate(unsigned int cpu)

{

	struct cppc_perf_fb_ctrs fb_ctrs_t0 = {0}, fb_ctrs_t1 = {0};
@@ -746,18 +767,32 @@ static unsigned int cppc_cpufreq_get_rate(unsigned int cpu) 


	cpufreq_cpu_put(policy);



	ret = cppc_get_perf_ctrs(cpu, &fb_ctrs_t0);

	if (ret)

		return 0;



	udelay(2); /* 2usec delay between sampling */



	ret = cppc_get_perf_ctrs(cpu, &fb_ctrs_t1);

	if (ret)

	ret = cppc_get_perf_ctrs_sample(cpu, &fb_ctrs_t0, &fb_ctrs_t1);

	if (ret) {

		if (ret == -EFAULT)

			/* Any of the associated CPPC regs is 0. */

			goto out_invalid_counters;

		else

			return 0;

	}



	delivered_perf = cppc_perf_from_fbctrs(cpu_data, &fb_ctrs_t0,

					       &fb_ctrs_t1);

	if (!delivered_perf)

		goto out_invalid_counters;



	return cppc_perf_to_khz(&cpu_data->perf_caps, delivered_perf);



out_invalid_counters:

	/*

	 * Feedback counters could be unchanged or 0 when a cpu enters a

	 * low-power idle state, e.g. clock-gated or power-gated.

	 * Use desired perf for reflecting frequency.  Get the latest register

	 * value first as some platforms may update the actual delivered perf

	 * there; if failed, resort to the cached desired perf.

	 */

	if (cppc_get_desired_perf(cpu, &delivered_perf))

		delivered_perf = cpu_data->perf_ctrls.desired_perf;



	return cppc_perf_to_khz(&cpu_data->perf_caps, delivered_perf);

}