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lib: sbi: hart: Detect existence of cycle and instret CSRs for Zicntr

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Zicntr extension specifies three read-only CSRs, time, cycle and
instret. It isn't sufficient to report Zicntr is fully supported with
only time CSR detected.

This patch introduces a bitmap to sbi_hart_features to record
availability of these CSRs, which are detected using traps. Zicntr is
reported as present if and only if three CSRs are all available on the
HARTs.

Sites originally depending on SBI_HART_EXT_ZICNTR for detecting
existence of time CSR are switched to detect SBI_HART_CSR_TIME instead.

Suggested-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Yao Zi <ziyao@disroot.org>
Reviewed-by: Anup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/20250516133352.36617-3-ziyao@disroot.org
Signed-off-by: Anup Patel <anup@brainfault.org>
This commit is contained in:
Yao Zi
2025-05-16 13:33:52 +00:00
committed by Anup Patel
parent 2bb7632649
commit 7e31dc8052
3 changed files with 39 additions and 8 deletions
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10
include/sbi/sbi_hart.h
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@@ -93,6 +93,14 @@ struct sbi_hart_ext_data {
extern const struct sbi_hart_ext_data sbi_hart_ext[];
/** CSRs should be detected by access and trapping */
enum sbi_hart_csrs {
SBI_HART_CSR_CYCLE = 0,
SBI_HART_CSR_TIME,
SBI_HART_CSR_INSTRET,
SBI_HART_CSR_MAX,
};
/*
* Smepmp enforces access boundaries between M-mode and
* S/U-mode. When it is enabled, the PMPs are programmed
@@ -112,6 +120,7 @@ struct sbi_hart_features {
bool detected;
int priv_version;
unsigned long extensions[BITS_TO_LONGS(SBI_HART_EXT_MAX)];
unsigned long csrs[BITS_TO_LONGS(SBI_HART_CSR_MAX)];
unsigned int pmp_count;
unsigned int pmp_addr_bits;
unsigned int pmp_log2gran;
@@ -150,6 +159,7 @@ bool sbi_hart_has_extension(struct sbi_scratch *scratch,
enum sbi_hart_extensions ext);
void sbi_hart_get_extensions_str(struct sbi_scratch *scratch,
char *extension_str, int nestr);
bool sbi_hart_has_csr(struct sbi_scratch *scratch, enum sbi_hart_csrs csr);
void __attribute__((noreturn)) sbi_hart_hang(void);