[PATCH 4/5] ata: ahci: do not enable LPM on external ports

[Niklas Cassel <cassel@kernel.org>]

The SATA specification contains a known incompatibility between LPM and
hot-plug events, thus do not enable LPM if the port advertises itself as
being an external SATA port (i.e. either hot-plug capable or eSATA).

This matches the power policy used in Microsoft Windows, which disables
LPM for external SATA ports, such that hot-plug events can be received.

Signed-off-by: Niklas Cassel <cassel@kernel.org>
---
 drivers/ata/ahci.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
index 19b605c98d42..d50d1ae44e7f 100644
--- a/drivers/ata/ahci.c
+++ b/drivers/ata/ahci.c
@@ -1664,6 +1664,14 @@ static void ahci_update_initial_lpm_policy(struct ata_port *ap)
 	if (!(hpriv->flags & AHCI_HFLAG_USE_LPM_POLICY))
 		return;
 
+	/*
+	 * The SATA specification contains a known incompatibility between LPM
+	 * and hot-plug events, thus do not enable LPM if the port advertises
+	 * itself as an external port (i.e. either hot-plug capable or eSATA).
+	 */
+	if (ap->pflags & ATA_PFLAG_EXTERNAL)
+		return;
+
 	/* user modified policy via module param */
 	if (mobile_lpm_policy != -1) {
 		policy = mobile_lpm_policy;
-- 
2.43.0