3 files changed, 94 insertions, 4 deletions

diff --git a/src/arch/riscv/include/arch/encoding.h b/src/arch/riscv/include/arch/encoding.h
index 9f9d8ca5a8..d40446b84f 100644
--- a/src/arch/riscv/include/arch/encoding.h
+++ b/src/arch/riscv/include/arch/encoding.h
@@ -48,6 +48,11 @@
 #define MSTATUS32_SD        0x80000000
 #define MSTATUS64_SD        0x8000000000000000
 
+#define MIE_UTIE        0x00000010
+#define MIE_STIE        0x00000020
+#define MIE_HTIE        0x00000040
+#define MIE_MTIE        0x00000080
+
 #define SSTATUS_UIE         0x00000001
 #define SSTATUS_SIE         0x00000002
 #define SSTATUS_UPIE        0x00000010
@@ -126,6 +131,7 @@
 
 #define SIP_SSIP MIP_SSIP
 #define SIP_STIP MIP_STIP
+#define SIE_STIE MIE_STIE
 
 #define PRV_U 0
 #define PRV_S 1
diff --git a/src/arch/riscv/trap_handler.c b/src/arch/riscv/trap_handler.c
index c7a11c6b9c..56812090c5 100644
--- a/src/arch/riscv/trap_handler.c
+++ b/src/arch/riscv/trap_handler.c
@@ -20,6 +20,10 @@
 #include <mcall.h>
 #include <string.h>
 #include <vm.h>
+#include <commonlib/configstring.h>
+
+static uint64_t *time;
+static uint64_t *timecmp;
 
 void handle_supervisor_call(trapframe *tf) {
 	uintptr_t call = tf->gpr[17]; /* a7 */
@@ -70,7 +74,7 @@ void handle_supervisor_call(trapframe *tf) {
 			returnValue = mcall_query_memory(arg0, (memory_block_info*) arg1);
 			break;
 		default:
-			printk(BIOS_DEBUG, "ERROR! Unrecognized system call\n");
+			printk(BIOS_DEBUG, "ERROR! Unrecognized SBI call\n");
 			returnValue = 0;
 			break; // note: system call we do not know how to handle
 	}
@@ -130,8 +134,76 @@ static void print_trap_information(const trapframe *tf)
 	printk(BIOS_DEBUG, "Stored sp:          %p\n", (void*) tf->gpr[2]);
 }
 
-void trap_handler(trapframe *tf) {
+static void gettimer(void)
+{
+	query_result res;
+	const char *config;
+
+	config = configstring();
+	query_rtc(config, (uintptr_t *)&time);
+	if (!time)
+		die("Got timer interrupt but found no timer.");
+	res = query_config_string(config, "core{0{0{timecmp");
+	timecmp = (void *)get_uint(res);
+	if (!timecmp)
+		die("Got a timer interrupt but found no timecmp.");
+}
+
+static void interrupt_handler(trapframe *tf)
+{
+	uint64_t cause = tf->cause & ~0x8000000000000000ULL;
+	uint32_t ssip, ssie;
+
+	switch (cause) {
+	case IRQ_M_TIMER:
+		// The only way to reset the timer interrupt is to
+		// write mtimecmp. But we also have to ensure the
+		// comparison fails, for a long time, to let
+		// supervisor interrupt handler compute a new value
+		// and set it. Finally, it fires if mtimecmp is <=
+		// mtime, not =, so setting mtimecmp to 0 won't work
+		// to clear the interrupt and disable a new one. We
+		// have to set the mtimecmp far into the future.
+		// Akward!
+		//
+		// Further, maybe the platform doesn't have the
+		// hardware or the payload never uses it. We hold off
+		// querying some things until we are sure we need
+		// them. What to do if we can not find them? There are
+		// no good options.
+
+		// This hart may have disabled timer interrupts.  If
+		// so, just return. Kernels should only enable timer
+		// interrupts on one hart, and that should be hart 0
+		// at present, as we only search for
+		// "core{0{0{timecmp" above.
+		ssie = read_csr(sie);
+		if (!(ssie & SIE_STIE))
+			break;
+
+		if (!timecmp)
+			gettimer();
+		*timecmp = (uint64_t) -1;
+		ssip = read_csr(sip);
+		ssip |= SIP_STIP;
+		write_csr(sip, ssip);
+		break;
+	default:
+		printk(BIOS_EMERG, "======================================\n");
+		printk(BIOS_EMERG, "Coreboot: Unknown machine interrupt: 0x%llx\n",
+		       cause);
+		printk(BIOS_EMERG, "======================================\n");
+		print_trap_information(tf);
+		break;
+	}
+}
+void trap_handler(trapframe *tf)
+{
 	write_csr(mscratch, tf);
+	if (tf->cause & 0x8000000000000000ULL) {
+		interrupt_handler(tf);
+		return;
+	}
 
 	switch(tf->cause) {
 		case CAUSE_MISALIGNED_FETCH:
@@ -159,6 +231,9 @@ void trap_handler(trapframe *tf) {
 			handle_supervisor_call(tf);
 			break;
 		default:
+			printk(BIOS_EMERG, "================================\n");
+			printk(BIOS_EMERG, "Coreboot: can not handle a trap:\n");
+			printk(BIOS_EMERG, "================================\n");
 			print_trap_information(tf);
 			break;
 	}
diff --git a/src/arch/riscv/virtual_memory.c b/src/arch/riscv/virtual_memory.c
index 26a0169335..aceb72eebd 100644
--- a/src/arch/riscv/virtual_memory.c
+++ b/src/arch/riscv/virtual_memory.c
@@ -292,12 +292,21 @@ void initVirtualMemory(void) {
 void mstatus_init(void)
 {
 	uintptr_t ms = 0;
+
 	ms = INSERT_FIELD(ms, MSTATUS_FS, 3);
 	ms = INSERT_FIELD(ms, MSTATUS_XS, 3);
 	write_csr(mstatus, ms);
 
-	clear_csr(mip, MIP_MSIP);
-	set_csr(mie, MIP_MSIP);
+	// clear any pending timer interrupts.
+	clear_csr(mip,  MIP_STIP | MIP_SSIP);
+
+	// enable machine and supervisor timer and
+	// all other supervisor interrupts.
+	set_csr(mie, MIP_MTIP | MIP_STIP | MIP_SSIP);
+
+	// Delegate supervisor timer and other interrupts
+	// to supervisor mode.
+	set_csr(mideleg,  MIP_STIP | MIP_SSIP);
 
 	set_csr(medeleg, delegate);