[PATCH v4 09/16] riscv: Add Zic64b to cpufeature and hwprobe

[Guodong Xu]

From: Qingwei Hu <qingwei.hu at bytedance.com>

Zic64b mandates 64-byte naturally aligned cache blocks and is a
mandatory extension of the RVA22 and RVA23 profiles.  Allocate a
RISCV_ISA_EXT_ZIC64B id, parse "zic64b" from the ISA string with a
validate callback that requires each cbom/cbop/cboz cache block size to
be 64 bytes when it is present, and export it through hwprobe.

Link: https://lists.riscv.org/g/tech-unprivileged/topic/question_about_zic64b_and/119631059
Signed-off-by: Qingwei Hu <qingwei.hu at bytedance.com>
Co-developed-by: Guodong Xu <docular.xu at gmail.com>
Signed-off-by: Guodong Xu <docular.xu at gmail.com>
---
v4:
- Credit Qingwei Hu's earlier Zic64b cpufeature patch: set him as
  author, with Co-developed-by (Guodong Xu).
- Validate only the cbom/cbop/cboz block sizes that are present; Zic64b
  does not imply the CMO extensions (Conor, Qingwei, Greg).
- Add a Link: to Greg's confirmation on the tech-unprivileged list.
- Add the missing blank line before the ZIC64B hwprobe.rst entry
  (Andrew).
- Did not carry Andrew Jones's v3 Reviewed-by: the validation was
  rewritten (present block sizes only) and the patch is now authored by
  Qingwei, so it warrants a fresh review.
v3: New patch.
---
 Documentation/arch/riscv/hwprobe.rst  |  4 ++++
 arch/riscv/include/asm/hwcap.h        |  1 +
 arch/riscv/include/uapi/asm/hwprobe.h |  1 +
 arch/riscv/kernel/cpufeature.c        | 19 +++++++++++++++++++
 arch/riscv/kernel/sys_hwprobe.c       |  1 +
 5 files changed, 26 insertions(+)

diff --git a/Documentation/arch/riscv/hwprobe.rst b/Documentation/arch/riscv/hwprobe.rst
index fc68dea397aae..32a14331eb9de 100644
--- a/Documentation/arch/riscv/hwprobe.rst
+++ b/Documentation/arch/riscv/hwprobe.rst
@@ -425,3 +425,7 @@ The following keys are defined:
   * :c:macro:`RISCV_HWPROBE_EXT_B`: The B extension is supported, as defined
     in version 1.0 of the Bit-Manipulation ISA extensions, and implies the
     presence of the Zba, Zbb, and Zbs sub-extensions.
+
+  * :c:macro:`RISCV_HWPROBE_EXT_ZIC64B`: The Zic64b extension is supported,
+    as defined in the RISC-V Profiles specification starting from commit
+    b1d80660 ("Updated to ratified state.")
diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h
index 58523b3a1998a..36572c1ff438a 100644
--- a/arch/riscv/include/asm/hwcap.h
+++ b/arch/riscv/include/asm/hwcap.h
@@ -117,6 +117,7 @@
 #define RISCV_ISA_EXT_ZICCAMOA		107
 #define RISCV_ISA_EXT_ZICCIF		108
 #define RISCV_ISA_EXT_ZA64RS		109
+#define RISCV_ISA_EXT_ZIC64B		110
 
 #define RISCV_ISA_EXT_XLINUXENVCFG	127
 
diff --git a/arch/riscv/include/uapi/asm/hwprobe.h b/arch/riscv/include/uapi/asm/hwprobe.h
index 430dc49a82863..36ec8ab470423 100644
--- a/arch/riscv/include/uapi/asm/hwprobe.h
+++ b/arch/riscv/include/uapi/asm/hwprobe.h
@@ -122,6 +122,7 @@ struct riscv_hwprobe {
 #define		RISCV_HWPROBE_EXT_ZICCRSE	(1ULL << 4)
 #define		RISCV_HWPROBE_EXT_ZA64RS	(1ULL << 5)
 #define		RISCV_HWPROBE_EXT_B		(1ULL << 6)
+#define		RISCV_HWPROBE_EXT_ZIC64B	(1ULL << 7)
 
 /* Increase RISCV_HWPROBE_MAX_KEY when adding items. */
 
diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index e0197160af6dd..29dff41313e65 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -154,6 +154,24 @@ static int riscv_ext_zicbop_validate(const struct riscv_isa_ext_data *data,
 	return 0;
 }
 
+static int riscv_ext_zic64b_validate(const struct riscv_isa_ext_data *data,
+				     const unsigned long *isa_bitmap)
+{
+	/*
+	 * Zic64b mandates 64-byte naturally aligned cache blocks; cross-check the
+	 * cbom/cbop/cboz block-size (when declared) device-tree properties to
+	 * avoid inconsistency.
+	 */
+	if ((riscv_cbom_block_size && riscv_cbom_block_size != 64) ||
+	    (riscv_cbop_block_size && riscv_cbop_block_size != 64) ||
+	    (riscv_cboz_block_size && riscv_cboz_block_size != 64)) {
+		pr_err("Zic64b detected in ISA string, disabling as a CBO block size is not 64 bytes\n");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
 static int riscv_ext_f_validate(const struct riscv_isa_ext_data *data,
 				const unsigned long *isa_bitmap)
 {
@@ -524,6 +542,7 @@ const struct riscv_isa_ext_data riscv_isa_ext[] = {
 	__RISCV_ISA_EXT_SUPERSET(b, RISCV_ISA_EXT_B, riscv_b_exts),
 	__RISCV_ISA_EXT_SUPERSET_VALIDATE(v, RISCV_ISA_EXT_V, riscv_v_exts, riscv_ext_vector_float_validate),
 	__RISCV_ISA_EXT_DATA(h, RISCV_ISA_EXT_H),
+	__RISCV_ISA_EXT_DATA_VALIDATE(zic64b, RISCV_ISA_EXT_ZIC64B, riscv_ext_zic64b_validate),
 	__RISCV_ISA_EXT_SUPERSET_VALIDATE(zicbom, RISCV_ISA_EXT_ZICBOM, riscv_xlinuxenvcfg_exts, riscv_ext_zicbom_validate),
 	__RISCV_ISA_EXT_DATA_VALIDATE(zicbop, RISCV_ISA_EXT_ZICBOP, riscv_ext_zicbop_validate),
 	__RISCV_ISA_EXT_SUPERSET_VALIDATE(zicboz, RISCV_ISA_EXT_ZICBOZ, riscv_xlinuxenvcfg_exts, riscv_ext_zicboz_validate),
diff --git a/arch/riscv/kernel/sys_hwprobe.c b/arch/riscv/kernel/sys_hwprobe.c
index dcc102bf8f183..3e80e5551ae0d 100644
--- a/arch/riscv/kernel/sys_hwprobe.c
+++ b/arch/riscv/kernel/sys_hwprobe.c
@@ -211,6 +211,7 @@ static void hwprobe_isa_ext1(struct riscv_hwprobe *pair,
 		EXT_KEY(isainfo->isa, ZICCRSE, pair->value, missing);
 		EXT_KEY(isainfo->isa, ZA64RS, pair->value, missing);
 		EXT_KEY(isainfo->isa, B, pair->value, missing);
+		EXT_KEY(isainfo->isa, ZIC64B, pair->value, missing);
 	}
 
 	/* Now turn off reporting features if any CPU is missing it. */

-- 
2.43.0