lib: sbi: Detect number of bits implemented in mhpmcounter

RISC-V privilege specification allows the implementation to have less
than 64 bits.

Add a function to detect the number of implemented bits in mhpmcounter
dynamically at runtime.

Reviewed-by: Xiang W <wxjstz@126.com>
Reviewed-by: Anup Patel <anup.patel@wdc.com>
Signed-off-by: Atish Patra <atish.patra@wdc.com>

diff --git a/include/sbi/sbi_hart.h b/include/sbi/sbi_hart.h
index 9e317c5..0c18ef9 100644 (file)
--- a/include/sbi/sbi_hart.h
+++ b/include/sbi/sbi_hart.h
@@ -44,6 +44,7 @@ void sbi_hart_delegation_dump(struct sbi_scratch *scratch,
 unsigned int sbi_hart_pmp_count(struct sbi_scratch *scratch);
 unsigned long sbi_hart_pmp_granularity(struct sbi_scratch *scratch);
 unsigned int sbi_hart_pmp_addrbits(struct sbi_scratch *scratch);
+unsigned int sbi_hart_mhpm_bits(struct sbi_scratch *scratch);
 int sbi_hart_pmp_configure(struct sbi_scratch *scratch);
 bool sbi_hart_has_feature(struct sbi_scratch *scratch, unsigned long feature);
 void sbi_hart_get_features_str(struct sbi_scratch *scratch,

diff --git a/lib/sbi/sbi_hart.c b/lib/sbi/sbi_hart.c
index 9c01cf7..e8cd042 100644 (file)
--- a/lib/sbi/sbi_hart.c
+++ b/lib/sbi/sbi_hart.c
@@ -33,6 +33,7 @@ struct hart_features {
        unsigned int pmp_addr_bits;
        unsigned long pmp_gran;
        unsigned int mhpm_count;
+       unsigned int mhpm_bits;
 };
 static unsigned long hart_features_offset;
 
@@ -177,6 +178,14 @@ unsigned int sbi_hart_pmp_addrbits(struct sbi_scratch *scratch)
        return hfeatures->pmp_addr_bits;
 }
 
+unsigned int sbi_hart_mhpm_bits(struct sbi_scratch *scratch)
+{
+       struct hart_features *hfeatures =
+                       sbi_scratch_offset_ptr(scratch, hart_features_offset);
+
+       return hfeatures->mhpm_bits;
+}
+
 int sbi_hart_pmp_configure(struct sbi_scratch *scratch)
 {
        struct sbi_domain_memregion *reg;
@@ -330,6 +339,37 @@ static unsigned long hart_pmp_get_allowed_addr(void)
        return val;
 }
 
+static int hart_pmu_get_allowed_bits(void)
+{
+       unsigned long val = ~(0UL);
+       struct sbi_trap_info trap = {0};
+       int num_bits = 0;
+
+       /**
+        * It is assumed that platforms will implement same number of bits for
+        * all the performance counters including mcycle/minstret.
+        */
+       csr_write_allowed(CSR_MHPMCOUNTER3, (ulong)&trap, val);
+       if (!trap.cause) {
+               val = csr_read_allowed(CSR_MHPMCOUNTER3, (ulong)&trap);
+               if (trap.cause)
+                       return 0;
+       }
+       num_bits = __fls(val) + 1;
+#if __riscv_xlen == 32
+       csr_write_allowed(CSR_MHPMCOUNTER3H, (ulong)&trap, val);
+       if (!trap.cause) {
+               val = csr_read_allowed(CSR_MHPMCOUNTER3H, (ulong)&trap);
+               if (trap.cause)
+                       return num_bits;
+       }
+       num_bits += __fls(val) + 1;
+
+#endif
+
+       return num_bits;
+}
+
 static void hart_detect_features(struct sbi_scratch *scratch)
 {
        struct sbi_trap_info trap = {0};
@@ -395,9 +435,17 @@ __pmp_skip:
 
        /* Detect number of MHPM counters */
        __check_csr(CSR_MHPMCOUNTER3, 0, 1UL, mhpm_count, __mhpm_skip);
+       hfeatures->mhpm_bits = hart_pmu_get_allowed_bits();
+
        __check_csr_4(CSR_MHPMCOUNTER4, 0, 1UL, mhpm_count, __mhpm_skip);
        __check_csr_8(CSR_MHPMCOUNTER8, 0, 1UL, mhpm_count, __mhpm_skip);
        __check_csr_16(CSR_MHPMCOUNTER16, 0, 1UL, mhpm_count, __mhpm_skip);
+
+       /**
+        * No need to check for MHPMCOUNTERH for RV32 as they are expected to be
+        * implemented if MHPMCOUNTER is implemented.
+        */
+
 __mhpm_skip:
 
 #undef __check_csr_64