[Skiboot] [PATCH v2 2/2] mbox: Reduce default BMC timeouts

[Cyril Bur]

Rebooting a BMC can take 70 seconds. Skiboot cannot possibly spin for
70 seconds waiting for a BMC to come back. This also makes the current
default of 30 seconds a bit pointless, is it far too short to be a
worse case wait time but too long to avoid hitting hardlockup detectors
and wrecking havoc inside host linux.

Just change it to three seconds so that host linux will survive and
that, reads and writes will fail but at least the host stays up.

Also refactored the waiting loop just a bit so that it's easier to read.

Reported-by: Pridhiviraj Paidipeddi <ppaidipe at linux.vnet.ibm.com>
Tested-by: Pridhiviraj Paidipeddi <ppaidipe at linux.vnet.ibm.com>
Signed-off-by: Cyril Bur <cyril.bur at au1.ibm.com>
---
v2: Split this patch out from the other one and lowered the default
    timeout.

 libflash/mbox-flash.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/libflash/mbox-flash.c b/libflash/mbox-flash.c
index 7bff34c4..dd1f11c2 100644
--- a/libflash/mbox-flash.c
+++ b/libflash/mbox-flash.c
@@ -42,7 +42,7 @@
 /* Same technique as BUILD_BUG_ON from linux */
 #define CHECK_HANDLER_SIZE(handlers) ((void)sizeof(char[1 - 2*!!(ARRAY_SIZE(handlers) != (MBOX_COMMAND_COUNT + 1))]))
 
-#define MBOX_DEFAULT_TIMEOUT 30
+#define MBOX_DEFAULT_TIMEOUT 3 /* seconds */
 
 #define MSG_CREATE(init_command) { .command = init_command }
 
@@ -334,15 +334,14 @@ static int wait_for_bmc(struct mbox_flash_data *mbox_flash, unsigned int timeout
 {
 	unsigned long last = 1, start = tb_to_secs(mftb());
 	prlog(PR_TRACE, "Waiting for BMC\n");
-	while (mbox_flash->busy && timeout_sec) {
+	while (mbox_flash->busy && timeout_sec > last) {
 		long now = tb_to_secs(mftb());
 		if (now - start > last) {
-			timeout_sec--;
-			last = now - start;
 			if (last < timeout_sec / 2)
 				prlog(PR_TRACE, "Been waiting for the BMC for %lu secs\n", last);
 			else
 				prlog(PR_ERR, "BMC NOT RESPONDING %lu second wait\n", last);
+			last++;
 		}
 		/*
 		 * Both functions are important.
-- 
2.16.2