[PATCH] lib: sbi_pmu: disable IR and CY counter in SBI initialization

[Jessica Clarke]

On 11 Nov 2023, at 04:16, Inochi Amaoto <inochiama at outlook.com> wrote:
> 
> The default overflow behavior of INSTRET and CYCLE counter remains
> unclear when platform has a custom pmu_device with irq callback.
> For example, enabling the IR and CY events in the startup without
> setting related CSRs may cause missing interrupt and wrong event
> report for D1 soc.
> 
> Disable IR and CY counter in the startup and let OS manage them.

Is this not an ABI break? Maybe Linux doesn’t care, but other OSes like
FreeBSD assume the counters are working and make them usable by U-mode.
If they no longer count up then you will break that for all existing
FreeBSD kernels.

Please don’t change existing semantics.

Jess

> Signed-off-by: Inochi Amaoto <inochiama at outlook.com>
> ---
> lib/sbi/sbi_hart.c | 2 +-
> lib/sbi/sbi_pmu.c  | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/sbi/sbi_hart.c b/lib/sbi/sbi_hart.c
> index 29d6481..8a908d6 100644
> --- a/lib/sbi/sbi_hart.c
> +++ b/lib/sbi/sbi_hart.c
> @@ -64,7 +64,7 @@ static void mstatus_init(struct sbi_scratch *scratch)
> 
> /* All programmable counters will start running at runtime after S-mode request */
> if (sbi_hart_priv_version(scratch) >= SBI_HART_PRIV_VER_1_11)
> - csr_write(CSR_MCOUNTINHIBIT, 0xFFFFFFF8);
> + csr_write(CSR_MCOUNTINHIBIT, 0xFFFFFFFD);
> 
> /**
> * The mhpmeventn[h] CSR should be initialized with interrupt disabled
> diff --git a/lib/sbi/sbi_pmu.c b/lib/sbi/sbi_pmu.c
> index f4c8fc4..1e2fc01 100644
> --- a/lib/sbi/sbi_pmu.c
> +++ b/lib/sbi/sbi_pmu.c
> @@ -944,7 +944,7 @@ void sbi_pmu_set_device(const struct sbi_pmu_device *dev)
> void sbi_pmu_exit(struct sbi_scratch *scratch)
> {
> if (sbi_hart_priv_version(scratch) >= SBI_HART_PRIV_VER_1_11)
> - csr_write(CSR_MCOUNTINHIBIT, 0xFFFFFFF8);
> + csr_write(CSR_MCOUNTINHIBIT, 0xFFFFFFFD);
> 
> if (sbi_hart_priv_version(scratch) >= SBI_HART_PRIV_VER_1_10)
> csr_write(CSR_MCOUNTEREN, -1);
> -- 
> 2.42.1
> 
> 
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