[PATCH v2] libata: disable forced PORTS_IMPL for >= AHCI 1.3

[Tejun Heo]

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
---
Hello, Andy.

Can you please see whether this one works?

Thanks.

 drivers/ata/libahci.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/ata/libahci.c b/drivers/ata/libahci.c
index d61740e..a91432a 100644
--- a/drivers/ata/libahci.c
+++ b/drivers/ata/libahci.c
@@ -496,8 +496,9 @@ void ahci_save_initial_config(struct device *dev, struct ahci_host_priv *hpriv)
 		}
 	}
 
-	/* 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 >> 16) ||
+			  ((vers >> 16) == 1 && (vers & 0xFFFF) < 0x300))) {
 		port_map = (1 << ahci_nr_ports(cap)) - 1;
 		dev_warn(dev, "forcing PORTS_IMPL to 0x%x\n", port_map);