[PW_SID:1161805] arm64/cpufreq: report and track frequencies above 4.19 GHz - #2635
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[PW_SID:1161805] arm64/cpufreq: report and track frequencies above 4.19 GHz#2635linux-riscv-bot wants to merge 2 commits into
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arch_freq_get_on_cpu() computes the product of the frequency scale and the reference frequency as a u64, but assigns it to an unsigned int before shifting it back down: freq = scale * arch_scale_freq_ref(cpu); freq >>= SCHED_CAPACITY_SHIFT; The product is truncated to 32 bits before the shift, so the result wraps once arch_scale_freq_ref() exceeds 2^32 / SCHED_CAPACITY_SCALE, i.e. 4194304 kHz. On a Snapdragon X2 Elite (Glymur) laptop, whose boost OPP is 4723200 kHz, cpuinfo_avg_freq reports 524283 kHz instead of ~4723200 kHz while the CPU demonstrably runs at the boost frequency: a fixed workload completes in 1.72 s at the 4723200 kHz OPP versus 2.01 s at 4032000 kHz, matching the 1.171 frequency ratio. Keep the arithmetic in 64 bits until after the shift. Fixes: 16d1e27 ("arm64: Provide an AMU-based version of arch_freq_get_on_cpu") Signed-off-by: Oleg Keri <okerixx@gmail.com> Signed-off-by: Linux RISC-V bot <linux.riscv.bot@gmail.com>
capacity_freq_ref is latched from policy->cpuinfo.max_freq by init_cpu_capacity_callback() on CPUFREQ_CREATE_POLICY, and never updated afterwards. cpufreq_frequency_table_cpuinfo() excludes CPUFREQ_BOOST_FREQ entries while boost is disabled, so on a system that boots with boost off the latched value is the non-boost maximum. Enabling boost later raises policy->cpuinfo.max_freq but leaves capacity_freq_ref behind. Two things then go wrong on arm64, where the AMU drives frequency invariance. amu_scale_freq_tick() caps the computed scale at SCHED_CAPACITY_SCALE, so a CPU running above capacity_freq_ref saturates at 1024: the scheduler cannot tell a boosted CPU from one at the sustained maximum, and utilisation is underestimated. And arch_freq_get_on_cpu(), which reverses that computation, cannot report more than capacity_freq_ref, so cpuinfo_avg_freq is pinned to the non-boost maximum. On a Snapdragon X2 Elite (Glymur) laptop with a 4032000 kHz sustained and a 4723200 kHz boost OPP, cpuinfo_avg_freq reads exactly 4032000 while the CPU runs at 4723200; a fixed workload completes in 1.72 s rather than the 2.01 s that frequency would imply. Factor the update out of init_cpu_capacity_callback() into topology_update_freq_ref() and call it from policy_set_boost(), which is the common path for the global boost knob, the per-policy one, and the CPU online path. Signed-off-by: Oleg Keri <okerixx@gmail.com> Signed-off-by: Linux RISC-V bot <linux.riscv.bot@gmail.com>
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PR for series 1161805 applied to workflow__riscv__fixes
Name: arm64/cpufreq: report and track frequencies above 4.19 GHz
URL: https://patchwork.kernel.org/series/1161805/
Version: 3