[riscv] Support older SBI implementations

Fall back to attempting the legacy SBI console and shutdown calls if
the standard calls fail.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/arch/riscv/include/ipxe/sbi.h

@@ -73,7 +73,7 @@ sbi_ecall_0 ( int eid, int fid ) {
  *
  * @v eid		Extension ID
  * @v fid		Function ID
- * @v param0		Parameter 0
+ * @v p0		Parameter 0
  * @ret ret		Return value
  */
 static inline __attribute__ (( always_inline )) struct sbi_return
@@ -98,8 +98,8 @@ sbi_ecall_1 ( int eid, int fid, unsigned long p0 ) {
  *
  * @v eid		Extension ID
  * @v fid		Function ID
- * @v param0		Parameter 0
+ * @v p0		Parameter 0
- * @v param1		Parameter 1
+ * @v p1		Parameter 1
  * @ret ret		Return value
  */
 static inline __attribute__ (( always_inline )) struct sbi_return
@@ -124,9 +124,9 @@ sbi_ecall_2 ( int eid, int fid, unsigned long p0, unsigned long p1 ) {
  *
  * @v eid		Extension ID
  * @v fid		Function ID
- * @v param0		Parameter 0
+ * @v p0		Parameter 0
- * @v param1		Parameter 1
+ * @v p1		Parameter 1
- * @v param2		Parameter 2
+ * @v p2		Parameter 2
  * @ret ret		Return value
  */
 static inline __attribute__ (( always_inline )) struct sbi_return
@@ -148,9 +148,51 @@ sbi_ecall_3 ( int eid, int fid, unsigned long p0, unsigned long p1,
 	return ret;
 }
 
+/**
+ * Call supervisor with no parameters
+ *
+ * @v fid		Legacy function ID
+ * @ret ret		Return value
+ */
+static inline __attribute__ (( always_inline )) long
+sbi_legacy_ecall_0 ( int fid ) {
+	register unsigned long a7 asm ( "a7" ) = ( ( long ) fid );
+	register unsigned long a0 asm ( "a0" );
+
+	__asm__ __volatile__ ( "ecall"
+			       : "=r" ( a0 )
+			       : "r" ( a7 )
+			       : "memory" );
+	return a0;
+}
+
+/**
+ * Call supervisor with one parameter
+ *
+ * @v fid		Legacy function ID
+ * @v p0		Parameter 0
+ * @ret ret		Return value
+ */
+static inline __attribute__ (( always_inline )) long
+sbi_legacy_ecall_1 ( int fid, unsigned long p0 ) {
+	register unsigned long a7 asm ( "a7" ) = ( ( long ) fid );
+	register unsigned long a0 asm ( "a0" ) = p0;
+
+	__asm__ __volatile__ ( "ecall"
+			       : "+r" ( a0 )
+			       : "r" ( a7 )
+			       : "memory" );
+	return a0;
+}
+
 /** Convert an SBI error code to an iPXE status code */
 #define ESBI( error ) EPLATFORM ( EINFO_EPLATFORM, error )
 
+/** Legacy extensions */
+#define SBI_LEGACY_PUTCHAR 0x01		/**< Console Put Character */
+#define SBI_LEGACY_GETCHAR 0x02		/**< Console Get Character */
+#define SBI_LEGACY_SHUTDOWN 0x08	/**< System Shutdown */
+
 /** System reset extension */
 #define SBI_SRST SBI_EID ( 'S', 'R', 'S', 'T' )
 #define SBI_SRST_SYSTEM_RESET 0x00	/**< Reset system */

src/arch/riscv/interface/sbi/sbi_console.c

@@ -50,9 +50,15 @@ static unsigned char sbi_console_input;
  * @v character		Character to be printed
  */
 static void sbi_putchar ( int character ) {
+	struct sbi_return ret;
 
 	/* Write byte to console */
-	sbi_ecall_1 ( SBI_DBCN, SBI_DBCN_WRITE_BYTE, character );
+	ret = sbi_ecall_1 ( SBI_DBCN, SBI_DBCN_WRITE_BYTE, character );
+	if ( ! ret.error )
+		return;
+
+	/* Debug extension not supported: try legacy method */
+	sbi_legacy_ecall_1 ( SBI_LEGACY_PUTCHAR, character );
 }
 
 /**
@@ -82,6 +88,7 @@ static int sbi_getchar ( void ) {
  */
 static int sbi_iskey ( void ) {
 	struct sbi_return ret;
+	long key;
 
 	/* Do nothing if we already have a buffered character */
 	if ( sbi_console_input )
@@ -91,11 +98,18 @@ static int sbi_iskey ( void ) {
 	ret = sbi_ecall_3 ( SBI_DBCN, SBI_DBCN_READ,
 			    sizeof ( sbi_console_input ),
 			    virt_to_phys ( &sbi_console_input ), 0 );
-	if ( ret.error )
+	if ( ! ret.error )
-		return 0;
+		return ret.value;
 
-	/* Return number of characters read and buffered */
+	/* Debug extension not supported: try legacy method */
-	return ret.value;
+	key = sbi_legacy_ecall_0 ( SBI_LEGACY_GETCHAR );
+	if ( key > 0 ) {
+		sbi_console_input = key;
+		return key;
+	}
+
+	/* No character available */
+	return 0;
 }
 
 /** SBI console */

src/arch/riscv/interface/sbi/sbi_reboot.c

@@ -53,6 +53,10 @@ static void sbi_reboot ( int flags ) {
 	rc = -ESBI ( ret.error );
 	DBGC ( SBI_SRST, "SBI %s reset failed: %s\n",
 	       ( warm ? "warm" : "cold" ), strerror ( rc ) );
+
+	/* Try a legacy shutdown */
+	sbi_legacy_ecall_0 ( SBI_LEGACY_SHUTDOWN );
+	DBGC ( SBI_SRST, "SBI legacy shutdown failed\n" );
 }
 
 /**
@@ -71,6 +75,11 @@ static int sbi_poweroff ( void ) {
 	/* Any return is an error */
 	rc = -ESBI ( ret.error );
 	DBGC ( SBI_SRST, "SBI shutdown failed: %s\n", strerror ( rc ) );
+
+	/* Try a legacy shutdown */
+	sbi_legacy_ecall_0 ( SBI_LEGACY_SHUTDOWN );
+	DBGC ( SBI_SRST, "SBI legacy shutdown failed\n" );
+
 	return rc;
 }
 

src/arch/riscv/prefix/libprefix.S

@@ -80,6 +80,9 @@ prefix_virt:
 #define SBI_DBCN ( ( 'D' << 24 ) | ( 'B' << 16 ) | ( 'C' << 8 ) | 'N' )
 #define SBI_DBCN_WRITE_BYTE 0x02
 
+/* SBI legacy console putchar */
+#define SBI_LEGACY_PUTCHAR 0x01
+
 	.section ".prefix.print_message", "ax", @progbits
 	.globl	print_message
 print_message:
@@ -108,6 +111,10 @@ print_message_alt:
 	li	a7, SBI_DBCN
 	li	a6, SBI_DBCN_WRITE_BYTE
 	ecall
+	beqz	a0, 1b
+	lbu	a0, -1(t1)
+	li	a7, SBI_LEGACY_PUTCHAR
+	ecall
 	j	1b
 2:
 	/* Restore registers and return (via alternate link register) */
@@ -154,6 +161,17 @@ progress_\@:
  * Returns: none
  *
  */
+
+	/*
+	 * Convert a single nibble to an ASCII character
+	 */
+	.macro	nibble_to_ascii reg
+	addi	\reg, \reg, -10
+	bltz	\reg, dec_\@
+	addi	\reg, \reg, ( 'a' - ( '0' + 10 ) )
+dec_\@:	addi	\reg, \reg, ( '0' + 10 )
+	.endm
+
 	.section ".prefix.print_hex_value", "ax", @progbits
 	.globl	print_hex_value
 print_hex_value:
@@ -183,14 +201,16 @@ print_hex_value_alt:
 
 1:	/* Print each digit in turn */
 	srli	a0, t1, ( __riscv_xlen - 4 )
-	addi	a0, a0, -10
+	nibble_to_ascii a0
-	bltz	a0, 2f
-	addi	a0, a0, ( 'a' - ( '0' + 10 ) )
-2:	addi	a0, a0, ( '0' + 10 )
 	li	a7, SBI_DBCN
 	li	a6, SBI_DBCN_WRITE_BYTE
 	ecall
-	slli	t1, t1, 4
+	beqz	a0, 2f
+	srli	a0, t1, ( __riscv_xlen - 4 )
+	nibble_to_ascii a0
+	li	a7, SBI_LEGACY_PUTCHAR
+	ecall
+2:	slli	t1, t1, 4
 	addi	t2, t2, -4
 	bgtz	t2, 1b
 
@@ -1121,6 +1141,9 @@ install:
 #define SBI_SRST_SYSTEM_RESET 0x00
 #define SBI_RESET_COLD 0x00000001
 
+/* SBI legacy shutdown */
+#define SBI_LEGACY_SHUTDOWN 0x08
+
 	.section ".prefix.reset_system", "ax", @progbits
 	.globl	reset_system
 reset_system:
@@ -1133,9 +1156,14 @@ reset_system:
 	li	a0, SBI_RESET_COLD
 	mv	a1, zero
 	ecall
+	progress "(reset failed)\n"
+
+	/* Attempt legacy shutdown */
+	li	a7, SBI_LEGACY_SHUTDOWN
+	ecall
+	progress "(legacy shutdown failed)\n"
 
 	/* If reset failed, lock the system */
-	progress "(reset failed)\n"
 1:	wfi
 	j	1b
 	.size	reset_system, . - reset_system