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, 5 insertions, 0 deletions

diff --git a/drivers/scsi/isci/port.h b/drivers/scsi/isci/port.h
index f8bd1e8dbfea..861e8f72811b 100644
--- a/drivers/scsi/isci/port.h
+++ b/drivers/scsi/isci/port.h
@@ -111,6 +111,7 @@ struct isci_port {
 	u16 reserved_tag;
 	u32 started_request_count;
 	u32 assigned_device_count;
+	u32 hang_detect_users;
 	u32 not_ready_reason;
 	struct isci_phy *phy_table[SCI_MAX_PHYS];
 	struct isci_host *owning_controller;
@@ -269,6 +270,10 @@ void sci_port_get_attached_sas_address(
 	struct isci_port *iport,
 	struct sci_sas_address *sas_address);
 
+void sci_port_set_hang_detection_timeout(
+	struct isci_port *isci_port,
+	u32 timeout);
+
 void isci_port_formed(struct asd_sas_phy *);
 void isci_port_deformed(struct asd_sas_phy *);