[PATCH 3.16.y-ckt 058/129] libata: disable forced PORTS_IMPL for >= AHCI 1.3

[Luis Henriques]

3.16.7-ckt25 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Tejun Heo <tj@xxxxxxxxxx>

commit 566d1827df2ef0cbe921d3d6946ac3007b1a6938 upstream.

Some early controllers incorrectly reported zero ports in PORTS_IMPL
register and the ahci driver fabricates PORTS_IMPL from the number of
ports in those cases.  This hasn't mattered but with the new nvme
controllers there are cases where zero PORTS_IMPL is valid and should
be honored.

Disable the workaround for >= AHCI 1.3.

Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Reported-by: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Link: http://lkml.kernel.org/g/CALCETrU7yMvXEDhjAUShoHEhDwifJGapdw--BKxsP0jmjKGmRw@xxxxxxxxxxxxxx
Cc: Sergei Shtylyov <sergei.shtylyov@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Luis Henriques <luis.henriques@xxxxxxxxxxxxx>
---
 drivers/ata/libahci.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/ata/libahci.c b/drivers/ata/libahci.c
index a0bfdcfafd92..9b82d2b1afdf 100644
--- a/drivers/ata/libahci.c
+++ b/drivers/ata/libahci.c
@@ -500,8 +500,8 @@ void ahci_save_initial_config(struct device *dev,
 		}
 	}
 
-	/* fabricate port_map from cap.nr_ports */
-	if (!port_map) {
+	/* fabricate port_map from cap.nr_ports for < AHCI 1.3 */
+	if (!port_map && vers < 0x10300) {
 		port_map = (1 << ahci_nr_ports(cap)) - 1;
 		dev_warn(dev, "forcing PORTS_IMPL to 0x%x\n", port_map);