I am working on a Raspberry Pi 5 (aarch64).
uname -a: Linux rpi5 6.8.0-1036-raspi #40-Ubuntu SMP PREEMPT_DYNAMIC Mon Aug 18 09:50:42 UTC 2025 aarch64 aarch64 aarch64 GNU/Linux
I load a kernel module I wrote. The same module was running on a Google Pixel 8, and the PMU configuration worked just fine. Now when I configure the pi whey just return a constant value of 0.
I have printed a bit of debug information from my kernel module:
This is the code I run to generate the above:
Additionally, This is the code I run to configure the PMUs:And this returnes that all of the pmevcntr{0-3}_el0 are equal to 0 constantly.
I downloaded perf to the pi, and it seem to work properly, and also I wrote a userland code which directly calls pef APIs and it seems to work as well.
Any help would be appriciated, Thanks!
uname -a: Linux rpi5 6.8.0-1036-raspi #40-Ubuntu SMP PREEMPT_DYNAMIC Mon Aug 18 09:50:42 UTC 2025 aarch64 aarch64 aarch64 GNU/Linux
I load a kernel module I wrote. The same module was running on a Google Pixel 8, and the PMU configuration worked just fine. Now when I configure the pi whey just return a constant value of 0.
I have printed a bit of debug information from my kernel module:
Code:
[71845.713814] PMCR_EL0: 0x00000000410b3001[71845.713816] Number of general-purpose counters: 7[71845.713817] Cycle counter exists: NO[71845.713818] Supported event IDs 0-31 : 0x000000007fff0f3f[71845.713820] Supported event IDs 32-63: 0x0000000000f2ae7f[71845.713821] PMCNTENSET_EL0: 0x000000000000000f[71845.713822] PMEVCNTR0_EL0 initial value: 0[71845.713824] PMEVCNTR1_EL0 initial value: 0[71845.713825] PMEVCNTR2_EL0 initial value: 0[71845.713826] PMEVCNTR3_EL0 initial value: 0[71845.713827] PMEVCNTR4_EL0 initial value: 0[71845.713829] PMEVCNTR5_EL0 initial value: 0[71845.713830] PMEVCNTR6_EL0 initial value: 0[71845.713831] PMCCNTR_EL0 initial value: 0Code:
static void pmu_discover(void *arg) { unsigned long flags = 0; uint64_t pmcr = 0, pmceid0 = 0, pmceid1 =0, n = 0, i = 0; preempt_disable(); local_irq_save(flags); asm volatile("mrs %0, pmcr_el0" : "=r"(pmcr)); pr_info("PMCR_EL0: 0x%016llx\n", pmcr); n = ((pmcr >> 11) & 0x1f) + 1; pr_info("Number of general-purpose counters: %llu\n", n); pr_info("Cycle counter exists: %s\n", (pmcr & (1<<31)) ? "YES" : "NO"); asm volatile("mrs %0, pmceid0_el0" : "=r"(pmceid0)); asm volatile("mrs %0, pmceid1_el0" : "=r"(pmceid1)); pr_info("Supported event IDs 0-31 : 0x%016llx\n", pmceid0); pr_info("Supported event IDs 32-63: 0x%016llx\n", pmceid1); uint64_t cntenset = 0; asm volatile("mrs %0, pmcntenset_el0" : "=r"(cntenset)); pr_info("PMCNTENSET_EL0: 0x%016llx\n", cntenset); for (i = 0; i < n; i++) { uint64_t val = 0; switch(i) { case 0: asm volatile("mrs %0, pmevcntr0_el0" : "=r"(val)); break; case 1: asm volatile("mrs %0, pmevcntr1_el0" : "=r"(val)); break; case 2: asm volatile("mrs %0, pmevcntr2_el0" : "=r"(val)); break; case 3: asm volatile("mrs %0, pmevcntr3_el0" : "=r"(val)); break; default: val = 0; break; } pr_info("PMEVCNTR%llu_EL0 initial value: %llu\n", i, val); } uint64_t cc = 0; asm volatile("mrs %0, pmccntr_el0" : "=r"(cc)); pr_info("PMCCNTR_EL0 initial value: %llu\n", cc); local_irq_restore(flags); preempt_enable();}Code:
static int config_pfc(void) { // filter EL0, EL2, EL3 uint64_t val = 0; uint64_t filter_events = (1 << 30) | (1 << 26); // disable PMU counters before selecting the event we want val = 0; asm volatile("mrs %0, pmcr_el0" : "=r" (val)); asm volatile("msr pmcr_el0, %0" :: "r" ((uint64_t)0x0)); asm volatile("isb\n"); asm volatile("msr pmcntenclr_el0, %0" :: "r" ((uint64_t)0b1111)); asm volatile("isb\n"); // select events: // 1. L1D cache refills (0x3) asm volatile("msr pmevtyper0_el0, %0" :: "r" ((uint64_t)(filter_events | 0x03))); asm volatile("isb\n"); // 2. Instructions retired (0x08) asm volatile("msr pmevtyper1_el0, %0" :: "r" ((uint64_t)(filter_events | 0x08))); asm volatile("isb\n"); // 3. Instruction speculatively executed (0x1b) asm volatile("msr pmevtyper2_el0, %0" :: "r" ((uint64_t)(filter_events | 0x1b))); asm volatile("isb\n"); // 4. L1D cache refills (0x3) asm volatile("msr pmevtyper3_el0, %0" :: "r" ((uint64_t)(filter_events | 0x3))); asm volatile("isb\n"); // enable counting val = 0; asm volatile("msr pmcntenset_el0, %0" :: "r" ((uint64_t)0b1111)); asm volatile("isb\n"); // enable PMU counters and reset the counters (using 3 bits) val = 0; asm volatile("mrs %0, pmcr_el0" : "=r" (val)); asm volatile("msr pmcr_el0, %0" :: "r" (val | 0b111)); asm volatile("isb\n"); // debug prints (view via 'sudo dmesg') for (volatile int i = 0; i < 1000000; i++) { } val = 0; asm volatile("mrs %0, pmuserenr_el0" : "=r" (val)); module_debug(KERN_ERR "%-24s 0x%0llx\n", "PMUSERENR_EL0:", val); asm volatile("mrs %0, pmcr_el0" : "=r" (val)); module_debug(KERN_ERR "%-24s 0x%0llx\n", "PMCR_EL0:", val); asm volatile("mrs %0, pmselr_el0" : "=r" (val)); module_debug(KERN_ERR "%-24s 0x%0llx\n", "PMSELR_EL0:", val); asm volatile("mrs %0, pmevtyper0_el0" : "=r" (val)); module_debug(KERN_ERR "%-24s 0x%0llx\n", "PMEVTYPER0_EL0:", val); asm volatile("mrs %0, pmcntenset_el0" : "=r" (val)); module_debug(KERN_ERR "%-24s 0x%0llx\n", "PMCNTENSET_EL0:", val); asm volatile("mrs %0, pmevcntr1_el0" : "=r" (val)); module_debug(KERN_ERR "%-24s 0x%0llx\n", "PMECNTR1_EL0:", val); asm volatile("mrs %0, pmevcntr2_el0" : "=r" (val)); module_debug(KERN_ERR "%-24s 0x%0llx\n", "PMECNTR2_EL0:", val); asm volatile("mrs %0, pmevcntr3_el0" : "=r" (val)); module_debug(KERN_ERR "%-24s 0x%0llx\n", "PMECNTR3_EL0:", val); asm volatile("mrs %0, pmccntr_el0" : "=r"(val)); module_debug(KERN_ERR "%-24s 0x%0llx\n", "PNCCNTR_EL0:", val); return 0;}I downloaded perf to the pi, and it seem to work properly, and also I wrote a userland code which directly calls pef APIs and it seems to work as well.
Any help would be appriciated, Thanks!
Statistics: Posted by 11gal — Sun Aug 31, 2025 1:46 pm — Replies 0 — Views 58