arm64/hwcap: Add support for FEAT_RPRFM

FEAT_RPRFM adds a new range prefetch hint within the existing PRFM space
for range prefetch hinting. Add a new hwcap to allow userspace to discover
support for the new instruction.

Signed-off-by: Mark Brown <[e-mail]>
Reviewed-by: Catalin Marinas <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Will Deacon <[e-mail]>

Documentation/arm64/elf_hwcaps.rst

···
 HWCAP2_CSSC
     Functionality implied by ID_AA64ISAR2_EL1.CSSC == 0b0001.
 
+HWCAP2_RPRFM
+    Functionality implied by ID_AA64ISAR2_EL1.RPRFM == 0b0001.
+
 4. Unused AT_HWCAP bits
 -----------------------
 

arch/arm64/include/asm/hwcap.h

···
 #define KERNEL_HWCAP_EBF16		__khwcap2_feature(EBF16)
 #define KERNEL_HWCAP_SVE_EBF16		__khwcap2_feature(SVE_EBF16)
 #define KERNEL_HWCAP_CSSC		__khwcap2_feature(CSSC)
+#define KERNEL_HWCAP_RPRFM		__khwcap2_feature(RPRFM)
 
 /*
  * This yields a mask that user programs can use to figure out what

arch/arm64/include/uapi/asm/hwcap.h

···
 #define HWCAP2_EBF16		(1UL << 32)
 #define HWCAP2_SVE_EBF16	(1UL << 33)
 #define HWCAP2_CSSC		(1UL << 34)
+#define HWCAP2_RPRFM		(1UL << 35)
 
 #endif /* _UAPI__ASM_HWCAP_H */

arch/arm64/kernel/cpufeature.c

···
 
 static const struct arm64_ftr_bits ftr_id_aa64isar2[] = {
 	ARM64_FTR_BITS(FTR_VISIBLE, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64ISAR2_EL1_CSSC_SHIFT, 4, 0),
+	ARM64_FTR_BITS(FTR_VISIBLE, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64ISAR2_EL1_RPRFM_SHIFT, 4, 0),
 	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_HIGHER_SAFE, ID_AA64ISAR2_EL1_BC_SHIFT, 4, 0),
 	ARM64_FTR_BITS(FTR_VISIBLE_IF_IS_ENABLED(CONFIG_ARM64_PTR_AUTH),
 		       FTR_STRICT, FTR_EXACT, ID_AA64ISAR2_EL1_APA3_SHIFT, 4, 0),
···
 	HWCAP_CAP(SYS_ID_AA64MMFR0_EL1, ID_AA64MMFR0_EL1_ECV_SHIFT, 4, FTR_UNSIGNED, 1, CAP_HWCAP, KERNEL_HWCAP_ECV),
 	HWCAP_CAP(SYS_ID_AA64MMFR1_EL1, ID_AA64MMFR1_EL1_AFP_SHIFT, 4, FTR_UNSIGNED, 1, CAP_HWCAP, KERNEL_HWCAP_AFP),
 	HWCAP_CAP(SYS_ID_AA64ISAR2_EL1, ID_AA64ISAR2_EL1_CSSC_SHIFT, 4, FTR_UNSIGNED, ID_AA64ISAR2_EL1_CSSC_IMP, CAP_HWCAP, KERNEL_HWCAP_CSSC),
+	HWCAP_CAP(SYS_ID_AA64ISAR2_EL1, ID_AA64ISAR2_EL1_RPRFM_SHIFT, 4, FTR_UNSIGNED, ID_AA64ISAR2_EL1_RPRFM_IMP, CAP_HWCAP, KERNEL_HWCAP_RPRFM),
 	HWCAP_CAP(SYS_ID_AA64ISAR2_EL1, ID_AA64ISAR2_EL1_RPRES_SHIFT, 4, FTR_UNSIGNED, 1, CAP_HWCAP, KERNEL_HWCAP_RPRES),
 	HWCAP_CAP(SYS_ID_AA64ISAR2_EL1, ID_AA64ISAR2_EL1_WFxT_SHIFT, 4, FTR_UNSIGNED, ID_AA64ISAR2_EL1_WFxT_IMP, CAP_HWCAP, KERNEL_HWCAP_WFXT),
 #ifdef CONFIG_ARM64_SME

arch/arm64/kernel/cpuinfo.c

···
 	[KERNEL_HWCAP_EBF16]		= "ebf16",
 	[KERNEL_HWCAP_SVE_EBF16]	= "sveebf16",
 	[KERNEL_HWCAP_CSSC]		= "cssc",
+	[KERNEL_HWCAP_RPRFM]		= "rprfm",
 };
 
 #ifdef CONFIG_COMPAT

arch/arm64/tools/sysreg

···
 	0b0000	NI
 	0b0001	IMP
 EndEnum
-Res0	51:28
+Enum	51:48	RPRFM
+	0b0000	NI
+	0b0001	IMP
+EndEnum
+Res0	47:28
 Enum	27:24	PAC_frac
 	0b0000	NI
 	0b0001	IMP