diff options
| author | Atish Patra <atish.patra@wdc.com> | 2021-07-10 19:18:06 +0300 |
|---|---|---|
| committer | Anup Patel <anup@brainfault.org> | 2021-07-11 07:44:26 +0300 |
| commit | 9c9b4ad24bf5891272679a6e994c64463db8ca03 (patch) | |
| tree | c16842683e501f499693201a4884c338bb81c558 | |
| parent | 0829f2bc284c07576a0dc9a569beea2a2d68dc3d (diff) | |
| download | opensbi-9c9b4ad24bf5891272679a6e994c64463db8ca03.tar.xz | |
lib: sbi: Disable m/scounteren & enable mcountinhibit
Currently, all bits in mcountern are enabled unconditionally at boot time.
With SBI PMU extension, all the programmable counters should enabled only
during performance monitoring for a particular event. However, this is done
only if mcountinhibit is implemented because the supervisor mode can not
start/stop any event without mcountinhibit.
Similarly, supervisor should take care enabling scounteren which allows
U-mode to access programmable pmu counters. All the non-programmable ones
(CY, TM, IR) should be enabled in M-mode because some userspace may rely on
builtins such as __builtin_readcyclecounter. Supervisor OS can still disable
them during initial configuration.
Reviewed-by: Anup Patel <anup.patel@wdc.com>
Signed-off-by: Atish Patra <atish.patra@wdc.com>
| -rw-r--r-- | lib/sbi/sbi_hart.c | 25 |
1 files changed, 21 insertions, 4 deletions
diff --git a/lib/sbi/sbi_hart.c b/lib/sbi/sbi_hart.c index e8cd042..6254452 100644 --- a/lib/sbi/sbi_hart.c +++ b/lib/sbi/sbi_hart.c @@ -51,12 +51,29 @@ static void mstatus_init(struct sbi_scratch *scratch) csr_write(CSR_MSTATUS, mstatus_val); - /* Enable user/supervisor use of perf counters */ + /* Disable user mode usage of all perf counters except default ones (CY, TM, IR) */ if (misa_extension('S') && sbi_hart_has_feature(scratch, SBI_HART_HAS_SCOUNTEREN)) - csr_write(CSR_SCOUNTEREN, -1); - if (sbi_hart_has_feature(scratch, SBI_HART_HAS_MCOUNTEREN)) - csr_write(CSR_MCOUNTEREN, -1); + csr_write(CSR_SCOUNTEREN, 7); + + if (sbi_hart_has_feature(scratch, SBI_HART_HAS_MCOUNTEREN)) { + if (sbi_hart_has_feature(scratch, SBI_HART_HAS_MCOUNTINHIBIT)) + /** + * Just enable the default counters (CY, TM, IR) because + * some OS (e.g FreeBSD) expect them to be enabled. + * + * All other counters will be enabled at runtime after + * S-mode request. + */ + csr_write(CSR_MCOUNTEREN, 7); + else + /* Supervisor mode usage are enabled by default */ + csr_write(CSR_MCOUNTEREN, -1); + } + + /* All programmable counters will start running at runtime after S-mode request */ + if (sbi_hart_has_feature(scratch, SBI_HART_HAS_MCOUNTINHIBIT)) + csr_write(CSR_MCOUNTINHIBIT, 0xFFFFFFF8); /* Disable all interrupts */ csr_write(CSR_MIE, 0); |