libata: Check log page directory before accessing pages

When reading the NCQ Send/Recv log it might actually not
supported, thereby causing irritating messages
'READ LOG DMA EXT failed'.
Instead we should be reading the log directory first to
figure out if the log is actually supported before trying
to access it.
Signed-off-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

drivers/ata/libata-core.c

@@ -66,6 +66,7 @@
 #include <scsi/scsi_host.h>
 #include <linux/libata.h>
 #include <asm/byteorder.h>
+#include <asm/unaligned.h>
 #include <linux/cdrom.h>
 #include <linux/ratelimit.h>
 #include <linux/pm_runtime.h>
@@ -2083,7 +2084,23 @@ static void ata_dev_config_ncq_send_recv(struct ata_device *dev)
 {
 	struct ata_port *ap = dev->link->ap;
 	unsigned int err_mask;
+	int log_index = ATA_LOG_NCQ_SEND_RECV * 2;
+	u16 log_pages;
 
+	err_mask = ata_read_log_page(dev, ATA_LOG_DIRECTORY,
+				     0, ap->sector_buf, 1);
+	if (err_mask) {
+		ata_dev_dbg(dev,
+			    "failed to get Log Directory Emask 0x%x\n",
+			    err_mask);
+		return;
+	}
+	log_pages = get_unaligned_le16(&ap->sector_buf[log_index]);
+	if (!log_pages) {
+		ata_dev_warn(dev,
+			     "NCQ Send/Recv Log not supported\n");
+		return;
+	}
 	err_mask = ata_read_log_page(dev, ATA_LOG_NCQ_SEND_RECV,
 				     0, ap->sector_buf, 1);
 	if (err_mask) {

include/linux/ata.h

@@ -314,6 +314,7 @@ enum {
 	ATA_SUBCMD_FPDMA_SEND_WR_LOG_DMA_EXT = 0x02,
 
 	/* READ_LOG_EXT pages */
+	ATA_LOG_DIRECTORY	= 0x0,
 	ATA_LOG_SATA_NCQ	= 0x10,
 	ATA_LOG_NCQ_SEND_RECV	  = 0x13,
 	ATA_LOG_SATA_ID_DEV_DATA  = 0x30,