riscv: add ISA parsing for Zca, Zcf, Zcd and Zcb

The Zc* standard extension for code reduction introduces new extensions.
This patch adds support for Zca, Zcf, Zcd and Zcb. Zce, Zcmt and Zcmp
are left out of this patch since they are targeting microcontrollers/
embedded CPUs instead of application processors.

Signed-off-by: Clément Léger <cleger@rivosinc.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20240619113529.676940-9-cleger@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

Author: clementleger

arch/riscv/include/asm/hwcap.h

@@ -87,6 +87,10 @@
 #define RISCV_ISA_EXT_ZVE64F		78
 #define RISCV_ISA_EXT_ZVE64D		79
 #define RISCV_ISA_EXT_ZIMOP		80
+#define RISCV_ISA_EXT_ZCA		81
+#define RISCV_ISA_EXT_ZCB		82
+#define RISCV_ISA_EXT_ZCD		83
+#define RISCV_ISA_EXT_ZCF		84
 
 #define RISCV_ISA_EXT_XLINUXENVCFG	127
 

arch/riscv/kernel/cpufeature.c

@@ -111,6 +111,9 @@ static int riscv_ext_zicboz_validate(const struct riscv_isa_ext_data *data,
 
 #define __RISCV_ISA_EXT_DATA(_name, _id) _RISCV_ISA_EXT_DATA(_name, _id, NULL, 0, NULL)
 
+#define __RISCV_ISA_EXT_DATA_VALIDATE(_name, _id, _validate) \
+			_RISCV_ISA_EXT_DATA(_name, _id, NULL, 0, _validate)
+
 /* Used to declare pure "lasso" extension (Zk for instance) */
 #define __RISCV_ISA_EXT_BUNDLE(_name, _bundled_exts) \
 	_RISCV_ISA_EXT_DATA(_name, RISCV_ISA_EXT_INVALID, _bundled_exts, \
@@ -122,6 +125,37 @@ static int riscv_ext_zicboz_validate(const struct riscv_isa_ext_data *data,
 #define __RISCV_ISA_EXT_SUPERSET_VALIDATE(_name, _id, _sub_exts, _validate) \
 	_RISCV_ISA_EXT_DATA(_name, _id, _sub_exts, ARRAY_SIZE(_sub_exts), _validate)
 
+static int riscv_ext_zca_depends(const struct riscv_isa_ext_data *data,
+				 const unsigned long *isa_bitmap)
+{
+	if (__riscv_isa_extension_available(isa_bitmap, RISCV_ISA_EXT_ZCA))
+		return 0;
+
+	return -EPROBE_DEFER;
+}
+static int riscv_ext_zcd_validate(const struct riscv_isa_ext_data *data,
+				  const unsigned long *isa_bitmap)
+{
+	if (__riscv_isa_extension_available(isa_bitmap, RISCV_ISA_EXT_ZCA) &&
+	    __riscv_isa_extension_available(isa_bitmap, RISCV_ISA_EXT_d))
+		return 0;
+
+	return -EPROBE_DEFER;
+}
+
+static int riscv_ext_zcf_validate(const struct riscv_isa_ext_data *data,
+				  const unsigned long *isa_bitmap)
+{
+	if (IS_ENABLED(CONFIG_64BIT))
+		return -EINVAL;
+
+	if (__riscv_isa_extension_available(isa_bitmap, RISCV_ISA_EXT_ZCA) &&
+	    __riscv_isa_extension_available(isa_bitmap, RISCV_ISA_EXT_f))
+		return 0;
+
+	return -EPROBE_DEFER;
+}
+
 static const unsigned int riscv_zk_bundled_exts[] = {
 	RISCV_ISA_EXT_ZBKB,
 	RISCV_ISA_EXT_ZBKC,
@@ -236,6 +270,21 @@ static const unsigned int riscv_xlinuxenvcfg_exts[] = {
 	RISCV_ISA_EXT_XLINUXENVCFG
 };
 
+/*
+ * Zc* spec states that:
+ * - C always implies Zca
+ * - C+F implies Zcf (RV32 only)
+ * - C+D implies Zcd
+ *
+ * These extensions will be enabled and then validated depending on the
+ * availability of F/D RV32.
+ */
+static const unsigned int riscv_c_exts[] = {
+	RISCV_ISA_EXT_ZCA,
+	RISCV_ISA_EXT_ZCF,
+	RISCV_ISA_EXT_ZCD,
+};
+
 /*
  * The canonical order of ISA extension names in the ISA string is defined in
  * chapter 27 of the unprivileged specification.
@@ -282,7 +331,7 @@ const struct riscv_isa_ext_data riscv_isa_ext[] = {
 	__RISCV_ISA_EXT_DATA(f, RISCV_ISA_EXT_f),
 	__RISCV_ISA_EXT_DATA(d, RISCV_ISA_EXT_d),
 	__RISCV_ISA_EXT_DATA(q, RISCV_ISA_EXT_q),
-	__RISCV_ISA_EXT_DATA(c, RISCV_ISA_EXT_c),
+	__RISCV_ISA_EXT_SUPERSET(c, RISCV_ISA_EXT_c, riscv_c_exts),
 	__RISCV_ISA_EXT_SUPERSET(v, RISCV_ISA_EXT_v, riscv_v_exts),
 	__RISCV_ISA_EXT_DATA(h, RISCV_ISA_EXT_h),
 	__RISCV_ISA_EXT_SUPERSET_VALIDATE(zicbom, RISCV_ISA_EXT_ZICBOM, riscv_xlinuxenvcfg_exts,
@@ -301,6 +350,10 @@ const struct riscv_isa_ext_data riscv_isa_ext[] = {
 	__RISCV_ISA_EXT_DATA(zfa, RISCV_ISA_EXT_ZFA),
 	__RISCV_ISA_EXT_DATA(zfh, RISCV_ISA_EXT_ZFH),
 	__RISCV_ISA_EXT_DATA(zfhmin, RISCV_ISA_EXT_ZFHMIN),
+	__RISCV_ISA_EXT_DATA(zca, RISCV_ISA_EXT_ZCA),
+	__RISCV_ISA_EXT_DATA_VALIDATE(zcb, RISCV_ISA_EXT_ZCB, riscv_ext_zca_depends),
+	__RISCV_ISA_EXT_DATA_VALIDATE(zcd, RISCV_ISA_EXT_ZCD, riscv_ext_zcd_validate),
+	__RISCV_ISA_EXT_DATA_VALIDATE(zcf, RISCV_ISA_EXT_ZCF, riscv_ext_zcf_validate),
 	__RISCV_ISA_EXT_DATA(zba, RISCV_ISA_EXT_ZBA),
 	__RISCV_ISA_EXT_DATA(zbb, RISCV_ISA_EXT_ZBB),
 	__RISCV_ISA_EXT_DATA(zbc, RISCV_ISA_EXT_ZBC),