[PATCH 06/10] ata: ahci: Disable DIPM if host lacks support

[Damien Le Moal <dlemoal@kernel.org>]

The AHCI specification version 1.3.1 section 8.3.1.4 (Software
Requirements and Precedence) states that:

If CAP.SSC or CAP.PSC is cleared to ‘0’, software should disable
device-initiated power management by issuing the appropriate SET
FEATURES command to the device.

To satisfy this constraint and force ata_dev_configure to disable the
device DIPM feature, modify ahci_update_initial_lpm_policy() to set the
ATA_FLAG_NO_DIPM flag on ports that have a host with either the
ATA_HOST_NO_PART flag set or the ATA_HOST_NO_SSC flag set.

Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
---
 drivers/ata/ahci.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
index 1b4151d95888..0760fa47d90e 100644
--- a/drivers/ata/ahci.c
+++ b/drivers/ata/ahci.c
@@ -1780,6 +1780,13 @@ static void ahci_update_initial_lpm_policy(struct ata_port *ap)
 		return;
 	}
 
+	/* If no Partial or no Slumber, we cannot support DIPM. */
+	if ((ap->host->flags & ATA_HOST_NO_PART) ||
+	    (ap->host->flags & ATA_HOST_NO_SSC)) {
+		ata_port_dbg(ap, "Host does not support DIPM\n");
+		ap->flags |= ATA_FLAG_NO_DIPM;
+	}
+
 	/* If no LPM states are supported by the HBA, do not bother with LPM */
 	if ((ap->host->flags & ATA_HOST_NO_PART) &&
 	    (ap->host->flags & ATA_HOST_NO_SSC) &&
-- 
2.50.0