[PATCH v3 04/17] riscv: vector: Use vlenb from DT

[Charlie Jenkins]

If vlenb is provided in the device tree, prefer that over reading the
vlenb csr.

Signed-off-by: Charlie Jenkins <charlie at rivosinc.com>
---
 arch/riscv/include/asm/cpufeature.h |  2 ++
 arch/riscv/kernel/cpufeature.c      | 26 ++++++++++++++++++++++++++
 arch/riscv/kernel/vector.c          | 13 +++++++++----
 3 files changed, 37 insertions(+), 4 deletions(-)

diff --git a/arch/riscv/include/asm/cpufeature.h b/arch/riscv/include/asm/cpufeature.h
index 347805446151..809f61ffb667 100644
--- a/arch/riscv/include/asm/cpufeature.h
+++ b/arch/riscv/include/asm/cpufeature.h
@@ -31,6 +31,8 @@ DECLARE_PER_CPU(struct riscv_cpuinfo, riscv_cpuinfo);
 /* Per-cpu ISA extensions. */
 extern struct riscv_isainfo hart_isa[NR_CPUS];
 
+extern u32 riscv_vlenb_dt[NR_CPUS];
+
 void riscv_user_isa_enable(void);
 
 #if defined(CONFIG_RISCV_MISALIGNED)
diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index c6e27b45e192..48874aac4871 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -35,6 +35,8 @@ static DECLARE_BITMAP(riscv_isa, RISCV_ISA_EXT_MAX) __read_mostly;
 /* Per-cpu ISA extensions. */
 struct riscv_isainfo hart_isa[NR_CPUS];
 
+u32 riscv_vlenb_dt[NR_CPUS];
+
 /**
  * riscv_isa_extension_base() - Get base extension word
  *
@@ -656,6 +658,28 @@ static int __init riscv_isa_fallback_setup(char *__unused)
 early_param("riscv_isa_fallback", riscv_isa_fallback_setup);
 #endif
 
+static void riscv_set_vlenb_from_dt(void)
+{
+	int cpu;
+
+	for_each_possible_cpu(cpu) {
+		struct device_node *cpu_node;
+
+		cpu_node = of_cpu_device_node_get(cpu);
+		if (!cpu_node) {
+			pr_warn("Unable to find cpu node\n");
+			continue;
+		}
+
+		if (!of_property_read_u32(cpu_node, "riscv,vlenb", &riscv_vlenb_dt[cpu])) {
+			of_node_put(cpu_node);
+			continue;
+		}
+
+		of_node_put(cpu_node);
+	}
+}
+
 void __init riscv_fill_hwcap(void)
 {
 	char print_str[NUM_ALPHA_EXTS + 1];
@@ -675,6 +699,8 @@ void __init riscv_fill_hwcap(void)
 	} else {
 		int ret = riscv_fill_hwcap_from_ext_list(isa2hwcap);
 
+		riscv_set_vlenb_from_dt();
+
 		if (ret && riscv_isa_fallback) {
 			pr_info("Falling back to deprecated \"riscv,isa\"\n");
 			riscv_fill_hwcap_from_isa_string(isa2hwcap);
diff --git a/arch/riscv/kernel/vector.c b/arch/riscv/kernel/vector.c
index 6727d1d3b8f2..fb7f3ca80d9e 100644
--- a/arch/riscv/kernel/vector.c
+++ b/arch/riscv/kernel/vector.c
@@ -32,11 +32,16 @@ EXPORT_SYMBOL_GPL(riscv_v_vsize);
 int riscv_v_setup_vsize(void)
 {
 	unsigned long this_vsize;
+	int cpu = smp_processor_id();
 
-	/* There are 32 vector registers with vlenb length. */
-	riscv_v_enable();
-	this_vsize = csr_read(CSR_VLENB) * 32;
-	riscv_v_disable();
+	if (riscv_vlenb_dt[cpu]) {
+		this_vsize = riscv_vlenb_dt[cpu];
+	} else {
+		/* There are 32 vector registers with vlenb length. */
+		riscv_v_enable();
+		this_vsize = csr_read(CSR_VLENB) * 32;
+		riscv_v_disable();
+	}
 
 	if (!riscv_v_vsize) {
 		riscv_v_vsize = this_vsize;

-- 
2.44.0