lib: Fix CPU capabilities detection function

On some platforms, misa may not be implemented. On such a platform,
reading misa will get 0. At this time, platform is required to
implement a non-standard function to detect the CPU's capabilities.
Therefore, this modification add interfaces for non-standard function.

The MXL field of misa is always at the highest two bits, whether it
is a 32-bit 64-bit or a 128-bit machine. Therefore, this modification
fixes the use of a fixed offset to detect the machine length.

Signed-off-by: Xiang Wang <[email protected]>
Signed-off-by: Anup Patel <[email protected]>

2 files changed, 46 insertions, 10 deletions

diff --git a/include/sbi/riscv_asm.h b/include/sbi/riscv_asm.h
index 4f12c03b..04502e1f 100644
--- a/include/sbi/riscv_asm.h
+++ b/include/sbi/riscv_asm.h
@@ -159,22 +159,18 @@ void csr_write_num(int csr_num, unsigned long val);
 		__asm__ __volatile__("wfi" ::: "memory"); \
 	} while (0)
 
-static inline int misa_extension(char ext)
-{
-	return csr_read(CSR_MISA) & (1 << (ext - 'A'));
-}
+/* Determine CPU extension, return non-zero support */
+int misa_extension(char ext);
 
-static inline int misa_xlen(void)
-{
-	return ((long)csr_read(CSR_MISA) < 0) ? 64 : 32;
-}
+/* Get MXL field of misa, return -1 on error */
+int misa_xlen(void);
 
 static inline void misa_string(char *out, unsigned int out_sz)
 {
-	unsigned long i, val = csr_read(CSR_MISA);
+	unsigned long i;
 
 	for (i = 0; i < 26; i++) {
-		if (val & (1 << i)) {
+		if (misa_extension('A' + i)) {
 			*out = 'A' + i;
 			out++;
 		}
diff --git a/include/sbi/sbi_platform.h b/include/sbi/sbi_platform.h
index 01d4a854..beb2f237 100644
--- a/include/sbi/sbi_platform.h
+++ b/include/sbi/sbi_platform.h
@@ -76,6 +76,16 @@ struct sbi_platform_operations {
 	/** Platform final initialization */
 	int (*final_init)(bool cold_boot);
 
+	/** For platforms that do not implement misa, non-standard
+	 * methods are needed to determine cpu extension.
+	 */
+	int (*misa_check_extension)(char ext);
+
+	/** For platforms that do not implement misa, non-standard
+	 * methods are needed to get MXL field of misa.
+	 */
+	int (*misa_get_xlen)(void);
+
 	/** Get number of PMP regions for given HART */
 	u32 (*pmp_region_count)(u32 hartid);
 	/**
@@ -292,6 +302,36 @@ static inline int sbi_platform_final_init(const struct sbi_platform *plat,
 }
 
 /**
+ * Check CPU extension in MISA
+ *
+ * @param plat pointer to struct sbi_platform
+ * @param ext shorthand letter for CPU extensions
+ *
+ * @return zero for not-supported and non-zero for supported
+ */
+static inline int sbi_platform_misa_extension(const struct sbi_platform *plat,
+					      char ext)
+{
+	if (plat && sbi_platform_ops(plat)->misa_check_extension)
+		return sbi_platform_ops(plat)->misa_check_extension(ext);
+	return 0;
+}
+
+/**
+ * Get MXL field of MISA
+ *
+ * @param plat pointer to struct sbi_platform
+ *
+ * @return 1/2/3 on success and error code on failure
+ */
+static inline int sbi_platform_misa_xlen(const struct sbi_platform *plat)
+{
+	if (plat && sbi_platform_ops(plat)->misa_get_xlen)
+		return sbi_platform_ops(plat)->misa_get_xlen();
+	return -1;
+}
+
+/**
  * Get the number of PMP regions of a HART
  *
  * @param plat pointer to struct sbi_platform