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

commit 66a7cbc3 upstream.

Samsung pci-e SSDs on macbooks failed miserably on NCQ commands, so
67809f85 ("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>
Fixes: 67809f85 ("ahci: disable NCQ on Samsung pci-e SSDs on macbooks")
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

drivers/ata/ahci.c

@@ -60,6 +60,7 @@ enum board_ids {
 	/* 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 @@ static const struct ata_port_info ahci_port_info[] = {
 		.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 @@ static const struct pci_device_id ahci_pci_tbl[] = {
 	{ 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 },