isci: Manage the link layer hang detect timer for RNC suspensions.

For STP devices under certain protocol conditions, an RNC will not
suspend until the current transfer state is broken with a SYNC/ESC
sequence from the SCU.  The SYNC/ESC driven by expiration of the
SCU link layer hang detect timer, which has too small a dynamic
range to support slow SATA devices, so normally it is disabled.

This change enables the timer with the minimum period at the point
when the suspension is requested.

Note that there is potential collateral damage to other open
connections to slow SATA devices on the same port, since there
is no alternative but to enable the LLHANG timer on every phy in
the port for the current suspension request - there is no way to
tell on which phy the RNC in question is currently active.

Signed-off-by: Jeff Skirvin <jeffrey.d.skirvin@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 25 insertions, 1 deletions

diff --git a/drivers/scsi/isci/port.c b/drivers/scsi/isci/port.c
index 0a3aec118097..ed206c5a00a6 100644
--- a/drivers/scsi/isci/port.c
+++ b/drivers/scsi/isci/port.c
@@ -1548,6 +1548,29 @@ static void sci_port_failed_state_enter(struct sci_base_state_machine *sm)
 	isci_port_hard_reset_complete(iport, SCI_FAILURE_TIMEOUT);
 }
 
+void sci_port_set_hang_detection_timeout(struct isci_port *iport, u32 timeout)
+{
+	int phy_index;
+	u32 phy_mask = iport->active_phy_mask;
+
+	if (timeout)
+		++iport->hang_detect_users;
+	else if (iport->hang_detect_users > 1)
+		--iport->hang_detect_users;
+	else
+		iport->hang_detect_users = 0;
+
+	if (timeout || (iport->hang_detect_users == 0)) {
+		for (phy_index = 0; phy_index < SCI_MAX_PHYS; phy_index++) {
+			if ((phy_mask >> phy_index) & 1) {
+				writel(timeout,
+				       &iport->phy_table[phy_index]
+					  ->link_layer_registers
+					  ->link_layer_hang_detection_timeout);
+			}
+		}
+	}
+}
 /* --------------------------------------------------------------------------- */
 
 static const struct sci_base_state sci_port_state_table[] = {
@@ -1596,6 +1619,7 @@ void sci_port_construct(struct isci_port *iport, u8 index,
 
 	iport->started_request_count = 0;
 	iport->assigned_device_count = 0;
+	iport->hang_detect_users = 0;
 
 	iport->reserved_rni = SCU_DUMMY_INDEX;
 	iport->reserved_tag = SCI_CONTROLLER_INVALID_IO_TAG;
@@ -1733,7 +1757,7 @@ void isci_port_formed(struct asd_sas_phy *phy)
 	struct isci_host *ihost = phy->ha->lldd_ha;
 	struct isci_phy *iphy = to_iphy(phy);
 	struct asd_sas_port *port = phy->port;
-	struct isci_port *iport;
+	struct isci_port *iport = NULL;
 	unsigned long flags;
 	int i;