[SeaBIOS] [PATCH 4/4] stacks: There is no need to disable NMI if it is already disabled
Kevin O'Connor
kevin at koconnor.net
Tue May 16 18:14:51 CEST 2017
Don't write to the cmos index port on a mode switch if NMI is already
disabled. This reduces the number of outb() calls.
Signed-off-by: Kevin O'Connor <kevin at koconnor.net>
---
src/stacks.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)
diff --git a/src/stacks.c b/src/stacks.c
index f4d15ce..2fe1bfb 100644
--- a/src/stacks.c
+++ b/src/stacks.c
@@ -66,8 +66,10 @@ call32_prep(u8 method)
// Backup cmos index register and disable nmi
u8 cmosindex = inb(PORT_CMOS_INDEX);
- outb(cmosindex | NMI_DISABLE_BIT, PORT_CMOS_INDEX);
- inb(PORT_CMOS_DATA);
+ if (!(cmosindex & NMI_DISABLE_BIT)) {
+ outb(cmosindex | NMI_DISABLE_BIT, PORT_CMOS_INDEX);
+ inb(PORT_CMOS_DATA);
+ }
SET_LOW(Call16Data.cmosindex, cmosindex);
SET_LOW(Call16Data.method, method);
@@ -103,8 +105,11 @@ call32_post(void)
}
// Restore cmos index register
- outb(GET_LOW(Call16Data.cmosindex), PORT_CMOS_INDEX);
- inb(PORT_CMOS_DATA);
+ u8 cmosindex = GET_LOW(Call16Data.cmosindex);
+ if (!(cmosindex & NMI_DISABLE_BIT)) {
+ outb(cmosindex, PORT_CMOS_INDEX);
+ inb(PORT_CMOS_DATA);
+ }
return method;
}
--
2.9.3
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