arch/riscv: Implement the SBI again

Not all SBI calls are implemented, but it's enough to see a couple dozen
lines of Linux boot output.

It should also be noted that the SBI is still in flux:
https://groups.google.com/a/groups.riscv.org/forum/#!topic/sw-dev/6oNhlW0OFKM

Change-Id: I80e4fe508336d6428ca7136bc388fbc3cda4f1e4
Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Reviewed-on: https://review.coreboot.org/16119
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

1 files changed, 117 insertions, 0 deletions

diff --git a/src/arch/riscv/sbi.S b/src/arch/riscv/sbi.S
new file mode 100644
index 0000000000..f4d5411879
--- /dev/null
+++ b/src/arch/riscv/sbi.S
@@ -0,0 +1,117 @@
+/*
+ * RISC-V supervisor binary interface (SBI) trampoline page
+ *
+ * Copyright 2016 Jonathan Neuschäfer <j.neuschaefer@gmx.net>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; version 2 of
+ * the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.See the
+ * GNU General Public License for more details.
+ */
+
+#define __ASSEMBLY__
+#include <arch/encoding.h>
+#include <arch/sbi.h>
+
+.section ".text.sbi", "ax", %progbits
+
+/* align to a page boundary */
+.align RISCV_PGSHIFT
+
+.globl sbi_page
+sbi_page:
+
+	/*
+	 * None of the SBI entry points is located in the first half of the
+	 * page
+	 */
+	.skip 0x800
+
+	/* -2048: size_t sbi_hart_id(void); */
+	li a7, SBI_ECALL_HART_ID
+	ecall
+	jr ra
+	.align 4
+
+	/* -2032: size_t sbi_num_harts(void); */
+	li a7, SBI_ECALL_NUM_HARTS
+	ecall
+	jr ra
+	.align 4
+
+	/* -2016: unsigned long sbi_query_memory(unsigned long id,
+			memory_block_info *p); */
+	li a7, SBI_ECALL_QUERY_MEMORY
+	ecall
+	jr ra
+	.align 4
+
+	/* -2000: int sbi_console_putchar(uint8_t ch); */
+	li a7, SBI_ECALL_CONSOLE_PUT
+	ecall
+	jr ra
+	.align 4
+
+	/* -1984: int sbi_console_getchar(void); */
+	li a0, -1	/* failure: Coreboot doesn't support console input */
+	jr ra
+	.align 4
+
+	/* -1968: Not allocated */
+	ebreak
+	.align 4
+
+	/* -1952: int sbi_send_ipi(size_t hart_id); */
+	ebreak
+	.align 4
+
+	/* -1936: int bool sbi_clear_ipi(void); */
+	ebreak
+	.align 4
+
+	/* -1920: unsigned long sbi_timebase(void); */
+	li a0, 1000000000 /* I have no idea. */
+	jr ra
+	.align 4
+
+	/* -1904: void sbi_shutdown(void); */
+	li a7, SBI_ECALL_SHUTDOWN
+	ecall
+	jr ra
+	.align 4
+
+	/* -1888: void sbi_set_timer(unsigned long long stime_value); */
+	li a7, SBI_ECALL_SET_TIMER
+	ecall
+	jr ra
+	.align 4
+
+	/* -1872: int sbi_mask_interrupt(int which); */
+	ebreak
+	.align 4
+
+	/* -1856: int sbi_unmask_interrupt(int which); */
+	ebreak
+	.align 4
+
+	/* -1840: void sbi_remote_sfence_vm(const uintptr_t* harts,
+			size_t asid); */
+	ebreak
+	.align 4
+
+	/* -1824: void sbi_remote_sfence_vm_range(const uintptr_t* harts,
+			size_t asid, uintptr_t start, uintptr_t size); */
+	ebreak
+	.align 4
+
+	/* -1808: void sbi_remote_fence_i(const uintptr_t* harts); */
+	ebreak
+	.align 4
+
+/* Fill the remainder of the page */
+.align RISCV_PGSHIFT