[PATCH 2/2] ata: ahci: Protect users from setting policies their drives don't support

[Mario Limonciello]

As the default low power policy applies to more chipsets and drives, it's
important to make sure that drives actually support the policy that a user
selected in their kernel configuration.

If the drive doesn't support slumber, don't let the default policies
dependent upon slumber (`min_power` or `min_power_with_partial`) affect the
disk.

Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxx>
---
Changes from RFC v1 -> PATCH v1:
* Move the warning and protection from drives that don't support slumber further
  into the calling path.
 drivers/ata/libahci.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/ata/libahci.c b/drivers/ata/libahci.c
index 0ed484e04fd6..9dee721ed1fe 100644
--- a/drivers/ata/libahci.c
+++ b/drivers/ata/libahci.c
@@ -785,7 +785,15 @@ static int ahci_set_lpm(struct ata_link *link, enum ata_lpm_policy policy,
 		pp->intr_mask &= ~PORT_IRQ_PHYRDY;
 		writel(pp->intr_mask, port_mmio + PORT_IRQ_MASK);
 
-		sata_link_scr_lpm(link, policy, false);
+		if (policy >= ATA_LPM_MIN_POWER_WITH_PARTIAL &&
+		   !(hpriv->cap & HOST_CAP_SSC)) {
+			struct pci_dev *pdev = to_pci_dev(ap->host->dev);
+
+			dev_warn(&pdev->dev,
+				 "This drive doesn't support slumber; ignoring SATA policy\n");
+		} else {
+			sata_link_scr_lpm(link, policy, false);
+		}
 	}
 
 	if (hpriv->cap & HOST_CAP_ALPM) {
-- 
2.34.1