The comment above the yield() function suggests that yield()
allows interrupts for a short time. But yield() only briefly
enables interrupts if SeaBIOS was built without CONFIG_THREADS
or if yield() is called from the main thread. In order to
guarantee that interrupts were enabled once before yield()
returns in a background thread, the main thread must call
check_irqs() before every thread switch. The function
run_thread() also switches threads, but the call to check_irqs()
was forgotten. Add the missing check_irqs() call.
This fixes PS/2 keyboard initialization failures.
The code in src/hw/ps2port.c relies on yield() to briefly enable
interrupts. There is a comment above the yield() function in
__ps2_command(), where the author left a remark why the call to
yield() is actually needed.
Here is one of the call sequences leading to a PS/2 keyboard
initialization failure.
ps2_keyboard_setup()
|
ret = i8042_command(I8042_CMD_KBD_DISABLE, NULL);
# This command will register an interrupt if the PS/2 device
# controller raises interrupts for replies to a controller
# command.
|
ret = ps2_kbd_command(ATKBD_CMD_RESET_BAT, param);
|
ps2_command(0, command, param);
|
ret = __ps2_command(aux, command, param);
|
// Flush any interrupts already pending.
yield();
# yield() doesn't flush interrupts if the main thread
# hasn't reached wait_threads().
|
ret = ps2_sendbyte(aux, command, 1000);
# Reset the PS/2 keyboard controller and wait for
# PS2_RET_ACK.
|
ret = ps2_recvbyte(aux, 0, 4000);
|
for (;;) {
|
status = inb(PORT_PS2_STATUS);
# I8042_STR_OBF isn't set because the keyboard self
# test reply is still on wire.
|
yield();
# After a few yield()s the keyboard interrupt fires
# and clears the I8042_STR_OBF status bit. If the
# keyboard self test reply arrives before the
# interrupt fires the keyboard reply is lost and
# ps2_recvbyte() returns after the timeout.
}
Suggested-by: Kevin O'Connor <[email protected]>
Signed-off-by: Volker Rümelin <[email protected]>
---
src/stacks.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/src/stacks.c b/src/stacks.c
index 2fe1bfb..641b13f 100644
--- a/src/stacks.c
+++ b/src/stacks.c
@@ -549,7 +549,10 @@ __end_thread(struct thread_info *old)
dprintf(1, "All threads complete.\n");
}
-// Create a new thread and start executing 'func' in it.
+void VISIBLE16 check_irqs(void);
+
+// Create a new thread. Briefly permit irqs to occur and start
+// executing 'func' in the new thread.
void
run_thread(void (*func)(void*), void *data)
{
@@ -565,6 +568,10 @@ run_thread(void (*func)(void*), void *data)
thread->stackpos = (void*)thread + THREADSTACKSIZE;
struct thread_info *cur = getCurThread();
hlist_add_after(&thread->node, &cur->node);
+ if (cur == &MainThread)
+ // Permit irqs to fire
+ check_irqs();
+
asm volatile(
// Start thread
" pushl $1f\n" // store return pc
--
2.26.2
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