ahci: disable MSI instead of NCQ on Samsung pci-e SSDs on macbooks

Samsung pci-e SSDs on macbooks failed miserably on NCQ commands, so
67809f85d31e ("ahci: disable NCQ on Samsung pci-e SSDs on macbooks")
disabled NCQ on them.  It turns out that NCQ is fine as long as MSI is
not used, so let's turn off MSI and leave NCQ on.

Signed-off-by: Tejun Heo <tj@kernel.org>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=60731
Tested-by: <dorin@i51.org>
Tested-by: Imre Kaloz <kaloz@openwrt.org>
Cc: stable@vger.kernel.org
Fixes: 67809f85d31e ("ahci: disable NCQ on Samsung pci-e SSDs on macbooks")
diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
index 5f039f1..ef4b647 100644
--- a/drivers/ata/ahci.c
+++ b/drivers/ata/ahci.c
@@ -60,6 +60,7 @@
 	/* board IDs by feature in alphabetical order */
 	board_ahci,
 	board_ahci_ign_iferr,
+	board_ahci_nomsi,
 	board_ahci_noncq,
 	board_ahci_nosntf,
 	board_ahci_yes_fbs,
@@ -121,6 +122,13 @@
 		.udma_mask	= ATA_UDMA6,
 		.port_ops	= &ahci_ops,
 	},
+	[board_ahci_nomsi] = {
+		AHCI_HFLAGS	(AHCI_HFLAG_NO_MSI),
+		.flags		= AHCI_FLAG_COMMON,
+		.pio_mask	= ATA_PIO4,
+		.udma_mask	= ATA_UDMA6,
+		.port_ops	= &ahci_ops,
+	},
 	[board_ahci_noncq] = {
 		AHCI_HFLAGS	(AHCI_HFLAG_NO_NCQ),
 		.flags		= AHCI_FLAG_COMMON,
@@ -475,10 +483,10 @@
 	{ PCI_VDEVICE(ASMEDIA, 0x0612), board_ahci },	/* ASM1062 */
 
 	/*
-	 * Samsung SSDs found on some macbooks.  NCQ times out.
-	 * https://bugzilla.kernel.org/show_bug.cgi?id=60731
+	 * Samsung SSDs found on some macbooks.  NCQ times out if MSI is
+	 * enabled.  https://bugzilla.kernel.org/show_bug.cgi?id=60731
 	 */
-	{ PCI_VDEVICE(SAMSUNG, 0x1600), board_ahci_noncq },
+	{ PCI_VDEVICE(SAMSUNG, 0x1600), board_ahci_nomsi },
 
 	/* Enmotus */
 	{ PCI_DEVICE(0x1c44, 0x8000), board_ahci },