megaraid_sas: Do not fire MR_DCMD_PD_LIST_QUERY to controllers which do not support it

There was an issue reported by Lucz Geza on Dell Perc 6i. As per issue
reported, megaraid_sas driver goes into an infinite error reporting loop
as soon as there is a change in the status of one of the
arrays (degrade, resync online etc ).  Below are the error logs reported
continuously-

Jun 25 08:49:30 ns8 kernel: [  757.757017] megaraid_sas 0000:02:00.0: DCMD failed/not supported by firmware: megasas_get_pd_list 4115
Jun 25 08:49:30 ns8 kernel: [  757.778017] megaraid_sas 0000:02:00.0: DCMD failed/not supported by firmware: megasas_get_pd_list 4115
Jun 25 08:49:30 ns8 kernel: [  757.799017] megaraid_sas 0000:02:00.0: DCMD failed/not supported by firmware: megasas_get_pd_list 4115
Jun 25 08:49:30 ns8 kernel: [  757.820018] megaraid_sas 0000:02:00.0: DCMD failed/not supported by firmware: megasas_get_pd_list 4115
Jun 25 08:49:30 ns8 kernel: [  757.841018] megaraid_sas 0000:02:00.0: DCMD failed/not supported by firmware: megasas_get_pd_list 4115

This issue is very much specific to controllers which do not support
DCMD- MR_DCMD_PD_LIST_QUERY.  In case of any hotplugging/rescanning of
drives, AEN thread will be scheduled by driver and fire DCMD-
MR_DCMD_PD_LIST_QUERY and if this DCMD is failed then driver will fail
this event processing and will not go ahead for further events. This
will cause infinite loop of same event getting retried infinitely and
causing above mentioned logs.

Fix for this problem is: not to fire DCMD MR_DCMD_PD_LIST_QUERY for
controllers which do not support it and send DCMD SUCCESS status to AEN
function so that it can go ahead with other event processing.
Reported-by: Lucz Geza <geza@lucz.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Sumit Saxena <sumit.saxena@broadcom.com>
Reviewed-by: Tomas Henzl <thenzl@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/megaraid/megaraid_sas_base.c

@@ -4079,6 +4079,12 @@ megasas_get_pd_list(struct megasas_instance *instance)
 	struct MR_PD_ADDRESS *pd_addr;
 	dma_addr_t ci_h = 0;
 
+	if (instance->pd_list_not_supported) {
+		dev_info(&instance->pdev->dev, "MR_DCMD_PD_LIST_QUERY "
+		"not supported by firmware\n");
+		return ret;
+	}
+
 	cmd = megasas_get_cmd(instance);
 
 	if (!cmd) {