RVCK-Project · ieiao · Jul 29, 2026 · Jul 29, 2026 · Oct 9, 2023 · Nov 14, 2024
diff --git a/Documentation/arch/riscv/hwprobe.rst b/Documentation/arch/riscv/hwprobe.rst
@@ -354,3 +354,13 @@ The following keys are defined:
 
   * :c:macro:`RISCV_HWPROBE_MISALIGNED_VECTOR_UNSUPPORTED`: Misaligned vector accesses are
     not supported at all and will generate a misaligned address fault.
+
+* :c:macro:`RISCV_HWPROBE_KEY_VENDOR_EXT_THEAD_0`: A bitmask containing the
+  thead vendor extensions that are compatible with the
+  :c:macro:`RISCV_HWPROBE_BASE_BEHAVIOR_IMA`: base system behavior.
+
+  * T-HEAD
+
+    * :c:macro:`RISCV_HWPROBE_VENDOR_EXT_XTHEADVECTOR`: The xtheadvector vendor
+        extension is supported in the T-Head ISA extensions spec starting from
+	commit a18c801634 ("Add T-Head VECTOR vendor extension. ").
diff --git a/Documentation/devicetree/bindings/riscv/cpus.yaml b/Documentation/devicetree/bindings/riscv/cpus.yaml
@@ -26,6 +26,18 @@ description: |
 allOf:
   - $ref: /schemas/cpu.yaml#
   - $ref: extensions.yaml
+  - if:
+      not:
+        properties:
+          compatible:
+            contains:
+              enum:
+                - thead,c906
+                - thead,c910
+                - thead,c920
+    then:
+      properties:
+        thead,vlenb: false
 
 properties:
   compatible:
@@ -83,6 +95,13 @@ properties:
     description:
       The blocksize in bytes for the Zicboz cache operations.
 
+  thead,vlenb:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    description:
+      VLEN/8, the vector register length in bytes. This property is required on
+      thead systems where the vector register length is not identical on all harts, or
+      the vlenb CSR is not available.
+
   # RISC-V has multiple properties for cache op block sizes as the sizes
   # differ between individual CBO extensions
   cache-op-block-size: false

diff --git a/arch/riscv/Kconfig.vendor b/arch/riscv/Kconfig.vendor
@@ -16,4 +16,30 @@ config RISCV_ISA_VENDOR_EXT_ANDES
 	  If you don't know what to do here, say Y.
 endmenu
 
+menu "T-Head"
+config RISCV_ISA_VENDOR_EXT_THEAD
+	bool "T-Head vendor extension support"
+	select RISCV_ISA_VENDOR_EXT
+	default y
+	help
+	  Say N here to disable detection of and support for all T-Head vendor
+	  extensions. Without this option enabled, T-Head vendor extensions will
+	  not be detected at boot and their presence not reported to userspace.
+
+	  If you don't know what to do here, say Y.
+
+config RISCV_ISA_XTHEADVECTOR
+	bool "xtheadvector extension support"
+	depends on RISCV_ISA_VENDOR_EXT_THEAD
+	depends on RISCV_ISA_V
+	depends on FPU
+	default y
+	help
+	  Say N here if you want to disable all xtheadvector related procedures
+	  in the kernel. This will disable vector for any T-Head board that
+	  contains xtheadvector rather than the standard vector.
+
+	  If you don't know what to do here, say Y.
+endmenu
+
 endmenu
diff --git a/arch/riscv/boot/dts/allwinner/sun20i-d1s.dtsi b/arch/riscv/boot/dts/allwinner/sun20i-d1s.dtsi
@@ -25,6 +25,10 @@
 			mmu-type = "riscv,sv39";
 			operating-points-v2 = <&opp_table_cpu>;
 			riscv,isa = "rv64imafdc";
+			riscv,isa-base = "rv64i";
+			riscv,isa-extensions = "i", "m", "a", "f", "d", "c", "zicntr", "zicsr",
+					       "zifencei", "zihpm", "xtheadvector";
+			thead,vlenb = <16>;
 			#cooling-cells = <2>;
 
 			cpu0_intc: interrupt-controller {

diff --git a/arch/riscv/boot/dts/thead/th1520.dtsi b/arch/riscv/boot/dts/thead/th1520.dtsi
@@ -66,7 +66,11 @@
 		c910_0: cpu@0 {
 			compatible = "thead,c910", "riscv";
 			device_type = "cpu";
-			riscv,isa = "rv64imafdc";
+			riscv,isa = "rv64imafdc_xtheadvector";
+			riscv,isa-base = "rv64i";
+			riscv,isa-extensions = "i", "m", "a", "f", "d", "c", "zicntr", "zicsr",
+					       "zifencei", "zihpm", "xtheadvector";
+			thead,vlenb = <16>;
 			reg = <0>;
 			i-cache-block-size = <64>;
 			i-cache-size = <65536>;
@@ -99,7 +103,11 @@
 		c910_1: cpu@1 {
 			compatible = "thead,c910", "riscv";
 			device_type = "cpu";
-			riscv,isa = "rv64imafdc";
+			riscv,isa = "rv64imafdc_xtheadvector";
+			riscv,isa-base = "rv64i";
+			riscv,isa-extensions = "i", "m", "a", "f", "d", "c", "zicntr", "zicsr",
+					       "zifencei", "zihpm", "xtheadvector";
+			thead,vlenb = <16>;
 			reg = <1>;
 			i-cache-block-size = <64>;
 			i-cache-size = <65536>;
@@ -130,7 +138,11 @@
 		c910_2: cpu@2 {
 			compatible = "thead,c910", "riscv";
 			device_type = "cpu";
-			riscv,isa = "rv64imafdc";
+			riscv,isa = "rv64imafdc_xtheadvector";
+			riscv,isa-base = "rv64i";
+			riscv,isa-extensions = "i", "m", "a", "f", "d", "c", "zicntr", "zicsr",
+					       "zifencei", "zihpm", "xtheadvector";
+			thead,vlenb = <16>;
 			reg = <2>;
 			i-cache-block-size = <64>;
 			i-cache-size = <65536>;
@@ -161,7 +173,11 @@
 		c910_3: cpu@3 {
 			compatible = "thead,c910", "riscv";
 			device_type = "cpu";
-			riscv,isa = "rv64imafdc";
+			riscv,isa = "rv64imafdc_xtheadvector";
+			riscv,isa-base = "rv64i";
+			riscv,isa-extensions = "i", "m", "a", "f", "d", "c", "zicntr", "zicsr",
+					       "zifencei", "zihpm", "xtheadvector";
+			thead,vlenb = <16>;
 			reg = <3>;
 			i-cache-block-size = <64>;
 			i-cache-size = <65536>;

diff --git a/arch/riscv/include/asm/cpufeature.h b/arch/riscv/include/asm/cpufeature.h
@@ -34,6 +34,8 @@ DECLARE_PER_CPU(struct riscv_cpuinfo, riscv_cpuinfo);
 /* Per-cpu ISA extensions. */
 extern struct riscv_isainfo hart_isa[NR_CPUS];
 
+extern u32 thead_vlenb_of;
+
 void __init riscv_user_isa_enable(void);
 
 #define _RISCV_ISA_EXT_DATA(_name, _id, _subset_exts, _subset_exts_size, _validate) {	\

diff --git a/arch/riscv/include/asm/csr.h b/arch/riscv/include/asm/csr.h
@@ -30,6 +30,12 @@
 #define SR_VS_CLEAN	_AC(0x00000400, UL)
 #define SR_VS_DIRTY	_AC(0x00000600, UL)
 
+#define SR_VS_THEAD		_AC(0x01800000, UL) /* xtheadvector Status */
+#define SR_VS_OFF_THEAD		_AC(0x00000000, UL)
+#define SR_VS_INITIAL_THEAD	_AC(0x00800000, UL)
+#define SR_VS_CLEAN_THEAD	_AC(0x01000000, UL)
+#define SR_VS_DIRTY_THEAD	_AC(0x01800000, UL)
+
 #define SR_XS		_AC(0x00018000, UL) /* Extension Status */
 #define SR_XS_OFF	_AC(0x00000000, UL)
 #define SR_XS_INITIAL	_AC(0x00008000, UL)
@@ -301,6 +307,18 @@
 #define CSR_STIMECMP		0x14D
 #define CSR_STIMECMPH		0x15D
 
+/* zicfiss user mode csr.  CSR_SSP holds current shadow stack pointer */
+#define CSR_SSP			0x011
+
+/* xtheadvector symbolic CSR names */
+#define CSR_VXSAT		0x9
+#define CSR_VXRM		0xa
+
+/* xtheadvector CSR masks */
+#define CSR_VXRM_MASK		3
+#define CSR_VXRM_SHIFT		1
+#define CSR_VXSAT_MASK		1
+
 /* Supervisor-Level Window to Indirectly Accessed Registers (AIA) */
 #define CSR_SISELECT		0x150
 #define CSR_SIREG		0x151

diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h
@@ -49,7 +49,6 @@
 #define RISCV_ISA_EXT_ZICSR		40
 #define RISCV_ISA_EXT_ZIFENCEI		41
 #define RISCV_ISA_EXT_ZIHPM		42
-#define RISCV_ISA_EXT_XTHEADVECTOR	43
 #define RISCV_ISA_EXT_SMSTATEEN		44
 #define RISCV_ISA_EXT_ZICOND		45
 #define RISCV_ISA_EXT_ZBC		46

diff --git a/arch/riscv/include/asm/switch_to.h b/arch/riscv/include/asm/switch_to.h
@@ -113,7 +113,7 @@ do {							\
 	struct task_struct *__next = (next);		\
 	if (has_fpu())					\
 		__switch_to_fpu(__prev, __next);	\
-	if (has_vector())					\
+	if (has_vector() || has_xtheadvector())		\
 		__switch_to_vector(__prev, __next);	\
 	__switch_to_envcfg(__next);			\
 	__switch_sse_entry_task(__next);			\