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riscv: simplify timer interrupt handling 

Just disable the timer interrupt and notify supervisor.
To receive another timer interrupt just set timecmp and
enable machine mode timer interrupt again.

TEST=Run linux on sifive unleashed

Change-Id: I5d693f872bd492c9d0017b514882a4cebd5ccadd
Signed-off-by: Philipp Hug <philipp@hug.cx>
Reviewed-on: https://review.coreboot.org/29340
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>
This commit is contained in:
Philipp Hug 2018-10-29 21:32:51 +01:00 committed by Ronald G. Minnich
parent d4ab5bbc82
commit 1ed082bc8b
1 changed files with 8 additions and 51 deletions
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59
src/arch/riscv/trap_handler.c
View File

@ -20,9 +20,6 @@
#include <string.h>
#include <vm.h>
static uint64_t *time;
static uint64_t *timecmp;
static const char *const exception_names[] = {
"Instruction address misaligned",
"Instruction access fault",
@ -78,62 +75,22 @@ static void print_trap_information(const trapframe *tf)
printk(BIOS_DEBUG, "Stored sp: %p\n", (void*) tf->gpr[2]);
}
static void gettimer(void)
{
/*
* FIXME: This hard-coded value (currently) works on spike, but we
* should really read it from the device tree.
*/
uintptr_t clint = 0x02000000;
time = (void *)(clint + 0xbff8);
timecmp = (void *)(clint + 0x4000);
if (!time)
die("Got timer interrupt but found no timer.");
if (!timecmp)
die("Got timer interrupt but found no timecmp.");
}
static void interrupt_handler(trapframe *tf)
{
uint64_t cause = tf->cause & ~0x8000000000000000ULL;
uint32_t msip, 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.
/*
* Set interrupt pending for supervisor mode and disable timer
* interrupt in machine mode.
* To receive another timer interrupt just set timecmp and
* enable machine mode timer interrupt again.
*/
// 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 & SIP_STIP))
break;
clear_csr(mie, MIP_MTIP);
set_csr(mip, MIP_STIP);
if (!timecmp)
gettimer();
//printk(BIOS_SPEW, "timer interrupt\n");
*timecmp = (uint64_t) -1;
msip = read_csr(mip);
msip |= SIP_STIP;
write_csr(mip, msip);
break;
default:
printk(BIOS_EMERG, "======================================\n");