linux-kernel - [PATCH v3 2/2] ata: ahci: Protect users from setting policies their drives don't support

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Date:   Mon, 4 Apr 2022 14:45:10 -0500
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 v3 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 policy for the
ATA port be `min_power` or `min_power_with_partial`.

Signed-off-by: Mario Limonciello <mario.limonciello@....com>
---
v2->v3:
 * Fix typo
 * Try to reset to CONFIG_SATA_LPM_POLICY unless that's too aggressive
   then take MED_POWER.
 drivers/ata/libata-sata.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/ata/libata-sata.c b/drivers/ata/libata-sata.c
index 044a16daa2d4..b41de7e03dce 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 +369,21 @@ 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)) {
+		policy = (CONFIG_SATA_LPM_POLICY < ATA_LPM_MIN_POWER_WITH_PARTIAL) ?
+			 CONFIG_SATA_LPM_POLICY : ATA_LPM_MED_POWER;
+		dev_warn(ap->host->dev,
+			"This drive doesn't support slumber; resetting policy to %d\n", policy);
+	}
+
 	rc = sata_scr_read(link, SCR_CONTROL, &scontrol);
 	if (rc)
 		return rc;
-- 
2.34.1