linux-kernel - [PATCH v2 2/2] ata: ahci: Protect users from setting policies their drives don't support

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Date:   Wed, 2 Mar 2022 21:49:12 -0600
From:   Mario Limonciello <mario.limonciello@....com>
To:     Damien Le Moal <damien.lemoal@...nsource.wdc.com>
CC:     "open list:LIBATA SUBSYSTEM (Serial and Parallel ATA drivers)" 
        <linux-ide@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        <hdegoede@...hat.com>,
        Mario Limonciello <mario.limonciello@....com>
Subject: [PATCH v2 2/2] ata: ahci: Protect users from setting policies their drives don't support

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@....com>
---
Changes from v1->v2:
* Move deeper into codepaths
* Reset to MED_POWER rather than ignore
 drivers/ata/libata-sata.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/ata/libata-sata.c b/drivers/ata/libata-sata.c
index 071158c0c44c..0dc03888c62b 100644
--- a/drivers/ata/libata-sata.c
+++ b/drivers/ata/libata-sata.c
@@ -13,6 +13,7 @@
 #include <scsi/scsi_device.h>
 #include <linux/libata.h>
 
+#include "ahci.h"
 #include "libata.h"
 #include "libata-transport.h"
 
@@ -368,10 +369,20 @@ int sata_link_scr_lpm(struct ata_link *link, enum ata_lpm_policy policy,
 		      bool spm_wakeup)
 {
 	struct ata_eh_context *ehc = &link->eh_context;
+	struct ata_port *ap = link->ap;
+	struct ahci_host_priv *hpriv;
 	bool woken_up = false;
 	u32 scontrol;
 	int rc;
 
+	hpriv = ap->host->private_data;
+	if (policy >= ATA_LPM_MIN_POWER_WITH_PARTIAL &&
+	  !(hpriv->cap & HOST_CAP_SSC)) {
+		dev_warn(ap->host->dev,
+			"This drive doesn't support slumber; restting policy to MED_POWER\n");
+		policy = ATA_LPM_MED_POWER;
+	}
+
 	rc = sata_scr_read(link, SCR_CONTROL, &scontrol);
 	if (rc)
 		return rc;
-- 
2.34.1