ata: libata: disallow dev-initiated LPM transitions to unsupported states

In AHCI 1.3.1, the register description for CAP.SSC:
"When cleared to ‘0’, software must not allow the HBA to initiate
transitions to the Slumber state via agressive link power management nor
the PxCMD.ICC field in each port, and the PxSCTL.IPM field in each port
must be programmed to disallow device initiated Slumber requests."

In AHCI 1.3.1, the register description for CAP.PSC:
"When cleared to ‘0’, software must not allow the HBA to initiate
transitions to the Partial state via agressive link power management nor
the PxCMD.ICC field in each port, and the PxSCTL.IPM field in each port
must be programmed to disallow device initiated Partial requests."

Ensure that we always set the corresponding bits in PxSCTL.IPM, such that
a device is not allowed to initiate transitions to power states which are
unsupported by the HBA.

DevSleep is always initiated by the HBA, however, for completeness, set the
corresponding bit in PxSCTL.IPM such that agressive link power management
cannot transition to DevSleep if DevSleep is not supported.

sata_link_scr_lpm() is used by libahci, ata_piix and libata-pmp.
However, only libahci has the ability to read the CAP/CAP2 register to see
if these features are supported. Therefore, in order to not introduce any
regressions on ata_piix or libata-pmp, create flags that indicate that the
respective feature is NOT supported. This way, the behavior for ata_piix
and libata-pmp should remain unchanged.

This change is based on a patch originally submitted by Runa Guo-oc.

Signed-off-by: Niklas Cassel <niklas.cassel@wdc.com>
Fixes: 1152b2617a6e ("libata: implement sata_link_scr_lpm() and make ata_dev_set_feature() global")
Cc: stable@vger.kernel.org
Signed-off-by: Damien Le Moal <dlemoal@kernel.org>

2 files changed, 25 insertions, 3 deletions

diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
index abb5911c9d09..08745e7db820 100644
--- a/drivers/ata/ahci.c
+++ b/drivers/ata/ahci.c
@@ -1883,6 +1883,15 @@ static int ahci_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
 	else
 		dev_info(&pdev->dev, "SSS flag set, parallel bus scan disabled\n");
 
+	if (!(hpriv->cap & HOST_CAP_PART))
+		host->flags |= ATA_HOST_NO_PART;
+
+	if (!(hpriv->cap & HOST_CAP_SSC))
+		host->flags |= ATA_HOST_NO_SSC;
+
+	if (!(hpriv->cap2 & HOST_CAP2_SDS))
+		host->flags |= ATA_HOST_NO_DEVSLP;
+
 	if (pi.flags & ATA_FLAG_EM)
 		ahci_reset_em(host);
 
diff --git a/drivers/ata/libata-sata.c b/drivers/ata/libata-sata.c
index 5d31c08be013..a701e1538482 100644
--- a/drivers/ata/libata-sata.c
+++ b/drivers/ata/libata-sata.c
@@ -396,10 +396,23 @@ int sata_link_scr_lpm(struct ata_link *link, enum ata_lpm_policy policy,
 	case ATA_LPM_MED_POWER_WITH_DIPM:
 	case ATA_LPM_MIN_POWER_WITH_PARTIAL:
 	case ATA_LPM_MIN_POWER:
-		if (ata_link_nr_enabled(link) > 0)
-			/* no restrictions on LPM transitions */
+		if (ata_link_nr_enabled(link) > 0) {
+			/* assume no restrictions on LPM transitions */
 			scontrol &= ~(0x7 << 8);
-		else {
+
+			/*
+			 * If the controller does not support partial, slumber,
+			 * or devsleep, then disallow these transitions.
+			 */
+			if (link->ap->host->flags & ATA_HOST_NO_PART)
+				scontrol |= (0x1 << 8);
+
+			if (link->ap->host->flags & ATA_HOST_NO_SSC)
+				scontrol |= (0x2 << 8);
+
+			if (link->ap->host->flags & ATA_HOST_NO_DEVSLP)
+				scontrol |= (0x4 << 8);
+		} else {
 			/* empty port, power off */
 			scontrol &= ~0xf;
 			scontrol |= (0x1 << 2);