On 25/01/2022 00:10, Mark Brown wrote:
Since all the fields in the main ID registers are 4 bits wide we have up
until now not bothered specifying the width in the code. Since we now
wish to use this mechanism to enumerate features from the floating point
feature registers which do not follow this pattern add a width to the
table. This means updating all the existing table entries but makes it
less likely that we run into issues in future due to implicitly assuming
a 4 bit width.
Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
Cc: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
---
arch/arm64/include/asm/cpufeature.h | 1 +
arch/arm64/kernel/cpufeature.c | 167 +++++++++++++++++-----------
2 files changed, 102 insertions(+), 66 deletions(-)
diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index ef6be92b1921..2728abd9cae4 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -356,6 +356,7 @@ struct arm64_cpu_capabilities {
struct { /* Feature register checking */
u32 sys_reg;
u8 field_pos;
+ u8 field_width;
u8 min_field_value;
u8 hwcap_type;
bool sign;
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index a46ab3b1c4d5..d9f09e40aaf6 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -1307,7 +1307,9 @@ u64 __read_sysreg_by_encoding(u32 sys_id)
static bool
feature_matches(u64 reg, const struct arm64_cpu_capabilities *entry)
{
- int val = cpuid_feature_extract_field(reg, entry->field_pos, entry->sign);
+ int val = cpuid_feature_extract_field_width(reg, entry->field_pos,
+ entry->field_width,
+ entry->sign);
Could we do something like :
+ int val = cpuid_feature_extract_field_width(reg, entry->field_pos,
entry->field_width ? : 4,
..
);
and leave the existing structures as they are ?
return val >= entry->min_field_value;
}
@@ -1952,6 +1954,7 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
There is arm64_errata[] array in cpu_errata.c. So, if we use the above
proposal we could leave things unchanged for all existing uses.
.matches = has_cpuid_feature,
.sys_reg = SYS_ID_AA64MMFR0_EL1,
.field_pos = ID_AA64MMFR0_ECV_SHIFT,
+ .field_width = 4,
.sign = FTR_UNSIGNED,
.min_field_value = 1,
},
...
-#define HWCAP_CPUID_MATCH(reg, field, s, min_value) \
+#define HWCAP_CPUID_MATCH(reg, field, width, s, min_value) \
.matches = has_cpuid_feature, \
.sys_reg = reg, \
.field_pos = field, \
+ .field_width = width, \
.sign = s, \
.min_field_value = min_value,
And that could avoid these changes too. We could add :
#define HWCAP_CPUID_MATCH_WIDTH(...)
when/if we need one, which sets the width.
Cheers
Suzuki
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