[PATCH 1/2] lib: sbi: hart: Detect existence of cycle and instret CSRs for Zicntr
Anup Patel
anup at brainfault.org
Tue Mar 25 01:15:25 PDT 2025
On Tue, Feb 25, 2025 at 10:14 PM Yao Zi <ziyao at disroot.org> wrote:
>
> Zicntr extension specifies three RO CSRs, time, cycle and instret. It
> isn't precise to report Zicntr is fully supported with only time CSR
> detected.
>
> Since CSR emulating code only cares about the availablity of time CSR,
> add additional definitions to represent the existance of cycle and
> instret CSRs.
>
> Signed-off-by: Yao Zi <ziyao at disroot.org>
> ---
> include/sbi/sbi_hart.h | 8 ++++++--
> lib/sbi/sbi_hart.c | 30 ++++++++++++++++++++++--------
> lib/sbi/sbi_timer.c | 2 +-
> 3 files changed, 29 insertions(+), 11 deletions(-)
>
> diff --git a/include/sbi/sbi_hart.h b/include/sbi/sbi_hart.h
> index 4c36c77..0a740cf 100644
> --- a/include/sbi/sbi_hart.h
> +++ b/include/sbi/sbi_hart.h
> @@ -37,8 +37,12 @@ enum sbi_hart_extensions {
> SBI_HART_EXT_SSCOFPMF,
> /** HART has Sstc extension */
> SBI_HART_EXT_SSTC,
> - /** HART has Zicntr extension (i.e. HW cycle, time & instret CSRs) */
> - SBI_HART_EXT_ZICNTR,
> + /** HART has HW time CSR, as specified in Zicntr extension */
> + SBI_HART_EXT_ZICNTR_TIME,
> + /** HART has HW cycle CSR, as specified in Zicntr extension */
> + SBI_HART_EXT_ZICNTR_CYCLE,
> + /** HART has HW instret CSR, as specified in Zicntr extension */
> + SBI_HART_EXT_ZICNTR_INSTRET,
Zicntr_time, Zicntr_cycle, and Zicntr_instret are not real extension
names so let's not add pseudo extension names.
Instead, I suggest introducing "enum sbi_hart_csrs" for CSRs
detected at boot-time. We will also need "csrs" bitmap in
"struct sbi_hart_features".
The new "enum sbi_hart_csrs" can have:
SBI_HART_CSR_CYCLE,
SBI_HART_CSR_TIME,
SBI_HART_CSR_INSTRET
These bits will be set in "struct sbi_hart_features" when
corresponding CSRs are detected at boot-time.
The SBI_HART_EXT_ZICNTR is only available when all
three SBI_HART_CSR_CYCLE, SBI_HART_CSR_TIME,
and SBI_HART_CSR_INSTRET are available.
> /** HART has Zihpm extension */
> SBI_HART_EXT_ZIHPM,
> /** HART has Zkr extension */
> diff --git a/lib/sbi/sbi_hart.c b/lib/sbi/sbi_hart.c
> index 8e2979b..e1d630d 100644
> --- a/lib/sbi/sbi_hart.c
> +++ b/lib/sbi/sbi_hart.c
> @@ -669,7 +669,9 @@ const struct sbi_hart_ext_data sbi_hart_ext[] = {
> __SBI_HART_EXT_DATA(smstateen, SBI_HART_EXT_SMSTATEEN),
> __SBI_HART_EXT_DATA(sscofpmf, SBI_HART_EXT_SSCOFPMF),
> __SBI_HART_EXT_DATA(sstc, SBI_HART_EXT_SSTC),
> - __SBI_HART_EXT_DATA(zicntr, SBI_HART_EXT_ZICNTR),
> + __SBI_HART_EXT_DATA(zicntr_time, SBI_HART_EXT_ZICNTR_TIME),
> + __SBI_HART_EXT_DATA(zicntr_cycle, SBI_HART_EXT_ZICNTR_CYCLE),
> + __SBI_HART_EXT_DATA(zicntr_instret, SBI_HART_EXT_ZICNTR_INSTRET),
> __SBI_HART_EXT_DATA(zihpm, SBI_HART_EXT_ZIHPM),
> __SBI_HART_EXT_DATA(zkr, SBI_HART_EXT_ZKR),
> __SBI_HART_EXT_DATA(smcntrpmf, SBI_HART_EXT_SMCNTRPMF),
> @@ -782,7 +784,7 @@ static int hart_detect_features(struct sbi_scratch *scratch)
> struct sbi_hart_features *hfeatures =
> sbi_scratch_offset_ptr(scratch, hart_features_offset);
> unsigned long val, oldval;
> - bool has_zicntr = false;
> + bool has_time = false, has_cycle = false, has_instret = false;
> int rc;
>
> /* If hart features already detected then do nothing */
> @@ -919,7 +921,13 @@ __pmp_skip:
> CSR_SCOUNTOVF, SBI_HART_EXT_SSCOFPMF);
> /* Detect if hart supports time CSR */
> __check_ext_csr(SBI_HART_PRIV_VER_UNKNOWN,
> - CSR_TIME, SBI_HART_EXT_ZICNTR);
> + CSR_TIME, SBI_HART_EXT_ZICNTR_TIME);
> + /* Detect if hart supports cycle CSR */
> + __check_ext_csr(SBI_HART_PRIV_VER_UNKNOWN,
> + CSR_CYCLE, SBI_HART_EXT_ZICNTR_CYCLE);
> + /* Detect if hart supports instret CSR */
> + __check_ext_csr(SBI_HART_PRIV_VER_UNKNOWN,
> + CSR_INSTRET, SBI_HART_EXT_ZICNTR_INSTRET);
> /* Detect if hart has AIA local interrupt CSRs */
> __check_ext_csr(SBI_HART_PRIV_VER_UNKNOWN,
> CSR_MTOPI, SBI_HART_EXT_SMAIA);
> @@ -938,8 +946,10 @@ __pmp_skip:
>
> #undef __check_ext_csr
>
> - /* Save trap based detection of Zicntr */
> - has_zicntr = sbi_hart_has_extension(scratch, SBI_HART_EXT_ZICNTR);
> + /* Save trap based detection of Zicntr CSRs */
> + has_time = sbi_hart_has_extension(scratch, SBI_HART_EXT_ZICNTR_TIME);
> + has_cycle = sbi_hart_has_extension(scratch, SBI_HART_EXT_ZICNTR_CYCLE);
> + has_instret = sbi_hart_has_extension(scratch, SBI_HART_EXT_ZICNTR_INSTRET);
>
> /* Let platform populate extensions */
> rc = sbi_platform_extensions_init(sbi_platform_thishart_ptr(),
> @@ -947,9 +957,13 @@ __pmp_skip:
> if (rc)
> return rc;
>
> - /* Zicntr should only be detected using traps */
> - __sbi_hart_update_extension(hfeatures, SBI_HART_EXT_ZICNTR,
> - has_zicntr);
> + /* Zicntr CSRs should only be detected using traps */
> + __sbi_hart_update_extension(hfeatures, SBI_HART_EXT_ZICNTR_TIME,
> + has_time);
> + __sbi_hart_update_extension(hfeatures, SBI_HART_EXT_ZICNTR_CYCLE,
> + has_cycle);
> + __sbi_hart_update_extension(hfeatures, SBI_HART_EXT_ZICNTR_INSTRET,
> + has_instret);
>
> /* Extensions implied by other extensions and features */
> if (hfeatures->mhpm_mask)
> diff --git a/lib/sbi/sbi_timer.c b/lib/sbi/sbi_timer.c
> index 86e0db5..b4db4ca 100644
> --- a/lib/sbi/sbi_timer.c
> +++ b/lib/sbi/sbi_timer.c
> @@ -190,7 +190,7 @@ int sbi_timer_init(struct sbi_scratch *scratch, bool cold_boot)
> if (!time_delta_off)
> return SBI_ENOMEM;
>
> - if (sbi_hart_has_extension(scratch, SBI_HART_EXT_ZICNTR))
> + if (sbi_hart_has_extension(scratch, SBI_HART_EXT_ZICNTR_TIME))
> get_time_val = get_ticks;
>
> ret = sbi_platform_timer_init(plat);
> --
> 2.48.1
>
>
> --
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Regards,
Anup
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