fsp: return OPAL_BUSY_EVENT on failure sending FSP_CMD_POWERDOWN_NORM

We had a race condition between FSP Reset/Reload and powering down
the system from the host:

Roughly:

  FSP                Host
  ---                ----
  Power on
                     Power on
  (inject EPOW)
  (trigger FSP R/R)
                     Processes EPOW event, starts shutting down
                     calls OPAL_CEC_POWER_DOWN
  (is still in R/R)
                     gets OPAL_INTERNAL_ERROR, spins in opal_poll_events
  (FSP comes back)
                     spinning in opal_poll_events
  (thinks host is running)

The call to OPAL_CEC_POWER_DOWN is only made once as the reset/reload
error path for fsp_sync_msg() is to return -1, which means we give
the OS OPAL_INTERNAL_ERROR, which is fine, except that our own API
docs give us the opportunity to return OPAL_BUSY when trying again
later may be successful, and we're ambiguous as to if you should retry
on OPAL_INTERNAL_ERROR.

For reference, the linux code looks like this:
>static void __noreturn pnv_power_off(void)
>{
>        long rc = OPAL_BUSY;
>
>        pnv_prepare_going_down();
>
>        while (rc == OPAL_BUSY || rc == OPAL_BUSY_EVENT) {
>                rc = opal_cec_power_down(0);
>                if (rc == OPAL_BUSY_EVENT)
>                        opal_poll_events(NULL);
>                else
>                        mdelay(10);
>        }
>        for (;;)
>                opal_poll_events(NULL);
>}

Which means that *practically* our only option is to return OPAL_BUSY
or OPAL_BUSY_EVENT.

We choose OPAL_BUSY_EVENT for FSP systems as we do want to ensure we're
running pollers to communicate with the FSP and do the final bits of
Reset/Reload handling before we power off the system.

Additionally, we really should update our documentation to point all
of these return codes and what action an OS should take.

CC: stable
Reported-by: Pridhiviraj Paidipeddi <ppaidipe@linux.vnet.ibm.com>
Signed-off-by: Stewart Smith <stewart@linux.vnet.ibm.com>
Reviewed-by: Vasant Hegde <hegdevasant@linux.vnet.ibm.com>
Acked-by: Ananth N Mavinakayanahalli <ananth@linux.vnet.ibm.com>
Signed-off-by: Stewart Smith <stewart@linux.vnet.ibm.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/platforms/ibm-fsp/common.c b/platforms/ibm-fsp/common.c
index 237b63f..0a9b06f 100644
--- a/platforms/ibm-fsp/common.c
+++ b/platforms/ibm-fsp/common.c
@@ -223,7 +223,7 @@ int64_t ibm_fsp_cec_power_down(uint64_t request)
 	printf("FSP: Sending shutdown command to FSP...\n");
 
 	if (fsp_sync_msg(fsp_mkmsg(FSP_CMD_POWERDOWN_NORM, 1, request), true))
-		return OPAL_INTERNAL_ERROR;
+		return OPAL_BUSY_EVENT;
 
 	fsp_reset_links();
 	return OPAL_SUCCESS;