[PATCH] powerpc/powernv: Fallback to old HMI handling behavior for old firmware

2014-10-06 Thread Mahesh J Salgaonkar 
From: Mahesh Salgaonkar mah...@linux.vnet.ibm.com

Recently we moved HMI handling into Linux kernel instead of taking
HMI directly in OPAL. This new change is dependent on new OPAL call
for HMI recovery which was introduced in newer firmware. While this new
change works fine with latest OPAL firmware, we broke the HMI handling
if we run newer kernel on old OPAL firmware that results in system hang.

This patch fixes this issue by falling back to old HMI behavior on older
OPAL firmware.

This patch introduces a check for opal token OPAL_HANDLE_HMI to see
if we are running on newer firmware or old firmware. On newer firmware
this check would return OPAL_TOKEN_PRESENT, otherwise we are running on
old firmware and fallback to old HMI behavior.

This patch depends on opal check token patch posted at ppc-devel
https://lists.ozlabs.org/pipermail/linuxppc-dev/2014-August/120224.html

Signed-off-by: Mahesh Salgaonkar mah...@linux.vnet.ibm.com
---
 arch/powerpc/platforms/powernv/opal.c |   18 ++
 1 file changed, 18 insertions(+)

diff --git a/arch/powerpc/platforms/powernv/opal.c 
b/arch/powerpc/platforms/powernv/opal.c
index b44eec3..2768cd3 100644
--- a/arch/powerpc/platforms/powernv/opal.c
+++ b/arch/powerpc/platforms/powernv/opal.c
@@ -194,6 +194,24 @@ static int __init opal_register_exception_handlers(void)
 * fwnmi area at 0x7000 to provide the glue space to OPAL
 */
glue = 0x7000;
+
+   /* Check if we are running on newer firmware that exports
+* OPAL_HANDLE_HMI token. If yes, then don't ask opal to patch
+* HMI interrupt and we catch it directly in Linux kernel.
+*
+* For older firmware we will fallback to old behavior and
+* let OPAL patch the HMI vector and handle it inside OPAL
+* firmware.
+*/
+   if (opal_check_token(OPAL_HANDLE_HMI) != OPAL_TOKEN_PRESENT) {
+   /* We are on old firmware. fallback to old behavior. */
+   pr_info(%s: Falling back to old HMI handling behavior.\n,
+   __func__);
+   opal_register_exception_handler(
+   OPAL_HYPERVISOR_MAINTENANCE_HANDLER,
+   0, glue);
+   glue += 128;
+   }
opal_register_exception_handler(OPAL_SOFTPATCH_HANDLER, 0, glue);
 #endif
 

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Re: [PATCH] powerpc/powernv: Fallback to old HMI handling behavior for old firmware

2014-10-06 Thread Stewart Smith 
Mahesh J Salgaonkar mah...@linux.vnet.ibm.com writes:
 From: Mahesh Salgaonkar mah...@linux.vnet.ibm.com

 Recently we moved HMI handling into Linux kernel instead of taking
 HMI directly in OPAL. This new change is dependent on new OPAL call
 for HMI recovery which was introduced in newer firmware. While this new
 change works fine with latest OPAL firmware, we broke the HMI handling
 if we run newer kernel on old OPAL firmware that results in system hang.

 This patch fixes this issue by falling back to old HMI behavior on older
 OPAL firmware.

 This patch introduces a check for opal token OPAL_HANDLE_HMI to see
 if we are running on newer firmware or old firmware. On newer firmware
 this check would return OPAL_TOKEN_PRESENT, otherwise we are running on
 old firmware and fallback to old HMI behavior.

 This patch depends on opal check token patch posted at ppc-devel
 https://lists.ozlabs.org/pipermail/linuxppc-dev/2014-August/120224.html

(just reviewed that patch before this one...)

 diff --git a/arch/powerpc/platforms/powernv/opal.c 
 b/arch/powerpc/platforms/powernv/opal.c
 index b44eec3..2768cd3 100644
 --- a/arch/powerpc/platforms/powernv/opal.c
 +++ b/arch/powerpc/platforms/powernv/opal.c
 @@ -194,6 +194,24 @@ static int __init opal_register_exception_handlers(void)
* fwnmi area at 0x7000 to provide the glue space to OPAL
*/
   glue = 0x7000;
 +
 + /* Check if we are running on newer firmware that exports
 +  * OPAL_HANDLE_HMI token. If yes, then don't ask opal to patch
 +  * HMI interrupt and we catch it directly in Linux kernel.
 +  *
 +  * For older firmware we will fallback to old behavior and
 +  * let OPAL patch the HMI vector and handle it inside OPAL
 +  * firmware.
 +  */
 + if (opal_check_token(OPAL_HANDLE_HMI) != OPAL_TOKEN_PRESENT) {
 + /* We are on old firmware. fallback to old behavior. */
 + pr_info(%s: Falling back to old HMI handling behavior.\n,
 + __func__);
 + opal_register_exception_handler(
 + OPAL_HYPERVISOR_MAINTENANCE_HANDLER,
 + 0, glue);
 + glue += 128;
 + }
   opal_register_exception_handler(OPAL_SOFTPATCH_HANDLER, 0,
 glue);

So.. that all looks fine, but another note: why are we doing the
OPAL_SOFTPATCH_HANDLER and why is it all #if 0 out in skiboot?

for this patch:

Reviewed-by: Stewart Smith stew...@linux.vnet.ibm.com

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