[PATCH v1 8/9] RISC-V: enable extension detection from new properties

[Conor Dooley]

Add support for parsing the new riscv,isa-extensions property in
riscv_fill_hwcap(), by means of a new "property" member of the
riscv_isa_ext_data struct. For now, this shadows the name of the
extension, however this may not be the case for all extensions.
For the sake of backwards compatibility, fall back to the old scheme
if the new properties are not detected. For now, just inform, rather
than warn, when that happens.

Signed-off-by: Conor Dooley <conor.dooley at microchip.com>
---
Naming things is hard, didn't know what to call the new function...
---
 arch/riscv/include/asm/hwcap.h |  1 +
 arch/riscv/kernel/cpufeature.c | 80 ++++++++++++++++++++++++++++++----
 2 files changed, 72 insertions(+), 9 deletions(-)

diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h
index 6ad896dc4342..e7f235868aa2 100644
--- a/arch/riscv/include/asm/hwcap.h
+++ b/arch/riscv/include/asm/hwcap.h
@@ -77,6 +77,7 @@ unsigned long riscv_get_elf_hwcap(void);
 struct riscv_isa_ext_data {
 	const unsigned int id;
 	const char *name;
+	const char *property;
 	const bool multi_letter;
 };
 
diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index 366477ba1eea..72eb757ad871 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -101,6 +101,7 @@ static bool riscv_isa_extension_check(int id)
 
 #define __RISCV_ISA_EXT_DATA(_name, _id, _multi) {	\
 	.name = #_name,					\
+	.property = #_name,				\
 	.id = _id,					\
 	.multi_letter = _multi,				\
 }
@@ -416,16 +417,66 @@ static void __init riscv_fill_hwcap_from_isa_string(unsigned long *isa2hwcap)
 		acpi_put_table((struct acpi_table_header *)rhct);
 }
 
+static int __init riscv_fill_hwcap_new(unsigned long *isa2hwcap)
+{
+	unsigned int cpu;
+
+	for_each_possible_cpu(cpu) {
+		unsigned long this_hwcap = 0;
+		struct device_node *cpu_node;
+		DECLARE_BITMAP(this_isa, RISCV_ISA_EXT_MAX);
+
+		cpu_node = of_cpu_device_node_get(cpu);
+		if (!cpu_node) {
+			pr_warn("Unable to find cpu node\n");
+			continue;
+		}
+
+		if (!of_property_present(cpu_node, "riscv,isa-extensions"))
+			continue;
+
+		for (int i = 0; i < riscv_isa_ext_count; i++) {
+			if (of_property_match_string(cpu_node, "riscv,isa-extensions",
+						     riscv_isa_ext[i].name) < 0)
+				continue;
+
+			if (!riscv_isa_extension_check(riscv_isa_ext[i].id))
+				continue;
+
+			if (!riscv_isa_ext[i].multi_letter)
+				this_hwcap |= isa2hwcap[riscv_isa_ext[i].id];
+
+			set_bit(riscv_isa_ext[i].id, this_isa);
+		}
+
+		of_node_put(cpu_node);
+
+		/*
+		 * All "okay" harts should have same isa. Set HWCAP based on
+		 * common capabilities of every "okay" hart, in case they don't.
+		 */
+		if (elf_hwcap)
+			elf_hwcap &= this_hwcap;
+		else
+			elf_hwcap = this_hwcap;
+
+		if (bitmap_empty(riscv_isa, RISCV_ISA_EXT_MAX))
+			bitmap_copy(riscv_isa, this_isa, RISCV_ISA_EXT_MAX);
+		else
+			bitmap_and(riscv_isa, riscv_isa, this_isa, RISCV_ISA_EXT_MAX);
+	}
+
+	if (bitmap_empty(riscv_isa, RISCV_ISA_EXT_MAX))
+		return -ENOENT;
+
+	return 0;
+}
+
 void __init riscv_fill_hwcap(void)
 {
-	struct device_node *node;
-	const char *isa;
 	char print_str[NUM_ALPHA_EXTS + 1];
-	int i, j, rc;
 	unsigned long isa2hwcap[26] = {0};
-	struct acpi_table_header *rhct;
-	acpi_status status;
-	unsigned int cpu;
+	int i, j;
 
 	isa2hwcap['i' - 'a'] = COMPAT_HWCAP_ISA_I;
 	isa2hwcap['m' - 'a'] = COMPAT_HWCAP_ISA_M;
@@ -435,10 +486,21 @@ void __init riscv_fill_hwcap(void)
 	isa2hwcap['c' - 'a'] = COMPAT_HWCAP_ISA_C;
 	isa2hwcap['v' - 'a'] = COMPAT_HWCAP_ISA_V;
 
-	riscv_fill_hwcap_from_isa_string(isa2hwcap);
+	if (!acpi_disabled) {
+		riscv_fill_hwcap_from_isa_string(isa2hwcap);
+	} else {
+		int ret = riscv_fill_hwcap_new(isa2hwcap);
 
-	/* We don't support systems with F but without D, so mask those out
-	 * here. */
+		if (ret) {
+			pr_info("Falling back to deprecated \"riscv,isa\"\n");
+			riscv_fill_hwcap_from_isa_string(isa2hwcap);
+		}
+	}
+
+	/*
+	 * We don't support systems with F but without D, so mask those out
+	 * here.
+	 */
 	if ((elf_hwcap & COMPAT_HWCAP_ISA_F) && !(elf_hwcap & COMPAT_HWCAP_ISA_D)) {
 		pr_info("This kernel does not support systems with F but not D\n");
 		elf_hwcap &= ~COMPAT_HWCAP_ISA_F;
-- 
2.40.1