Skip to content
Browse files

dcdbas: force SMI to happen when expected

The dcdbas driver can do an I/O write to cause a SMI to occur.  The SMI handler
looks at certain registers and memory locations, so the SMI needs to happen
immediately.  On some systems I/O writes are posted, though, causing the SMI to
happen well after the "outb" occurred, which causes random failures.  Following
the "outb" with an "inb" forces the write to go through even if it is posted.

Signed-off-by: Stuart Hayes <>
Acked-by: Doug Warzecha <>
Signed-off-by: Jiri Kosina <>
  • Loading branch information...
1 parent 19f5252 commit dd65c736d1b5312c80c88a64bf521db4959eded5 Stuart Hayes committed with Jiri Kosina Mar 2, 2011
Showing with 3 additions and 1 deletion.
  1. +3 −1 drivers/firmware/dcdbas.c
4 drivers/firmware/dcdbas.c
@@ -268,8 +268,10 @@ int dcdbas_smi_request(struct smi_cmd *smi_cmd)
/* generate SMI */
+ /* inb to force posted write through and make SMI happen now */
asm volatile (
- "outb %b0,%w1"
+ "outb %b0,%w1\n"
+ "inb %w1"
: /* no output args */
: "a" (smi_cmd->command_code),
"d" (smi_cmd->command_address),

0 comments on commit dd65c73

Please sign in to comment.
Something went wrong with that request. Please try again.