scsi: qla2xxx: Fix setting lower transfer speed if GPSC fails

commit 413c2f3 upstream.

This patch prevents driver from setting lower default speed of 1 GB/sec,
if the switch does not support Get Port Speed Capabilities (GPSC)
command. Setting this default speed results into much lower write
performance for large sequential WRITE.  This patch modifies driver to
check for gpsc_supported flags and prevents driver from issuing
MBC_SET_PORT_PARAM (001Ah) to set default speed of 1 GB/sec. If driver
does not send this mailbox command, firmware assumes maximum supported
link speed and will operate at the max speed.

Cc: [email protected]
Signed-off-by: Himanshu Madhani <[email protected]>
Reported-by: Eda Zhou <[email protected]>
Reviewed-by: Ewan D. Milne <[email protected]>
Tested-by: Ewan D. Milne <[email protected]>
Signed-off-by: Martin K. Petersen <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: Himanshu Madhani

drivers/scsi/qla2xxx/qla_init.c

@@ -4627,7 +4627,8 @@ qla2x00_iidma_fcport(scsi_qla_host_t *vha, fc_port_t *fcport)
 		return;
 
 	if (fcport->fp_speed == PORT_SPEED_UNKNOWN ||
-	    fcport->fp_speed > ha->link_data_rate)
+	    fcport->fp_speed > ha->link_data_rate ||
+	    !ha->flags.gpsc_supported)
 		return;
 
 	rval = qla2x00_set_idma_speed(vha, fcport->loop_id, fcport->fp_speed,