scsi: sd: Fix system start for ATA devices

It is not always possible to keep a device in the runtime suspended state
when a system level suspend/resume cycle is executed. E.g. for ATA devices
connected to AHCI adapters, system resume resets the ATA ports, which
causes connected devices to spin up. In such case, a runtime suspended disk
will incorrectly be seen with a suspended runtime state because the device
is not resumed by sd_resume_system(). The power state seen by the user is
different than the actual device physical power state.

Fix this issue by introducing the struct scsi_device flag
force_runtime_start_on_system_start. When set, this flag causes
sd_resume_system() to request a runtime resume operation for runtime
suspended devices. This results in the user seeing the device runtime_state
as active after a system resume, thus correctly reflecting the device
physical power state.

Fixes: 9131bff ("scsi: core: pm: Only runtime resume if necessary")
Cc: <[email protected]>
Signed-off-by: Damien Le Moal <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Martin K. Petersen <[email protected]>

Author: damien-lemoal

drivers/ata/libata-scsi.c

@@ -1055,9 +1055,14 @@ int ata_scsi_dev_config(struct scsi_device *sdev, struct ata_device *dev)
 		 * Ask the sd driver to issue START STOP UNIT on runtime suspend
 		 * and resume and shutdown only. For system level suspend/resume,
 		 * devices power state is handled directly by libata EH.
+		 * Given that disks are always spun up on system resume, also
+		 * make sure that the sd driver forces runtime suspended disks
+		 * to be resumed to correctly reflect the power state of the
+		 * device.
 		 */
 		sdev->manage_runtime_start_stop = 1;
 		sdev->manage_shutdown = 1;
+		sdev->force_runtime_start_on_system_start = 1;
 	}
 
 	/*

drivers/scsi/sd.c

@@ -3949,8 +3949,15 @@ static int sd_resume(struct device *dev, bool runtime)
 
 static int sd_resume_system(struct device *dev)
 {
-	if (pm_runtime_suspended(dev))
+	if (pm_runtime_suspended(dev)) {
+		struct scsi_disk *sdkp = dev_get_drvdata(dev);
+		struct scsi_device *sdp = sdkp ? sdkp->device : NULL;
+
+		if (sdp && sdp->force_runtime_start_on_system_start)
+			pm_request_resume(dev);
+
 		return 0;
+	}
 
 	return sd_resume(dev, false);
 }

include/scsi/scsi_device.h

@@ -181,6 +181,12 @@ struct scsi_device {
 	 */
 	unsigned manage_shutdown:1;
 
+	/*
+	 * If set and if the device is runtime suspended, ask the high-level
+	 * device driver (sd) to force a runtime resume of the device.
+	 */
+	unsigned force_runtime_start_on_system_start:1;
+
 	unsigned removable:1;
 	unsigned changed:1;	/* Data invalid due to media change */
 	unsigned busy:1;	/* Used to prevent races */