[PATCH v1 2/9] scsi: Allow auto suspend override by low-level driver

[Asutosh Das]

From: Sujit Reddy Thumma <sthumma@xxxxxxxxxxxxxx>

Until now the scsi mid-layer forbids runtime suspend till userspace
enables it. This is mainly to quarantine some disks with broken
runtime power management or have high latencies executing suspend
resume callbacks. If the userspace doesn't enable the runtime suspend
the underlying hardware will be always on even when it is not doing
any useful work and thus wasting power.

Some low-level drivers for the controllers can efficiently use runtime
power management to reduce power consumption and improve battery life.
Allow runtime suspend parameters override within the LLD itself
instead of waiting for userspace to control the power management.

Signed-off-by: Sujit Reddy Thumma <sthumma@xxxxxxxxxxxxxx>
Signed-off-by: Subhash Jadavani <subhashj@xxxxxxxxxxxxxx>
Signed-off-by: Asutosh Das <asutoshd@xxxxxxxxxxxxxx>
---
 drivers/scsi/scsi_scan.c   | 4 ++++
 drivers/scsi/scsi_sysfs.c  | 3 ++-
 drivers/scsi/sd.c          | 2 ++
 include/scsi/scsi_device.h | 3 +++
 4 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
index 0880d97..5b7232a 100644
--- a/drivers/scsi/scsi_scan.c
+++ b/drivers/scsi/scsi_scan.c
@@ -969,6 +969,10 @@ static int scsi_add_lun(struct scsi_device *sdev, unsigned char *inq_result,
 
 	transport_configure_device(&sdev->sdev_gendev);
 
+	/* The LLD can override auto suspend tunables in ->slave_configure() */
+	sdev->use_rpm_auto = 0;
+	sdev->autosuspend_delay = SCSI_DEFAULT_AUTOSUSPEND_DELAY;
+
 	if (sdev->host->hostt->slave_configure) {
 		ret = sdev->host->hostt->slave_configure(sdev);
 		if (ret) {
diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index 7943b76..706e778 100644
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -1266,7 +1266,8 @@ int scsi_sysfs_add_sdev(struct scsi_device *sdev)
 	device_enable_async_suspend(&sdev->sdev_gendev);
 	scsi_autopm_get_target(starget);
 	pm_runtime_set_active(&sdev->sdev_gendev);
-	pm_runtime_forbid(&sdev->sdev_gendev);
+	if (!sdev->use_rpm_auto)
+		pm_runtime_forbid(&sdev->sdev_gendev);
 	pm_runtime_enable(&sdev->sdev_gendev);
 	scsi_autopm_put_target(starget);
 
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index a6201e6..205624f 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -3269,6 +3269,8 @@ static void sd_probe_async(void *data, async_cookie_t cookie)
 	}
 
 	blk_pm_runtime_init(sdp->request_queue, dev);
+	if (sdp->autosuspend_delay >= 0)
+		pm_runtime_set_autosuspend_delay(dev, sdp->autosuspend_delay);
 	device_add_disk(dev, gd);
 	if (sdkp->capacity)
 		sd_dif_config_host(sdkp);
diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index 4c36af6..1d5ae90 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -197,7 +197,10 @@ struct scsi_device {
 	unsigned broken_fua:1;		/* Don't set FUA bit */
 	unsigned lun_in_cdb:1;		/* Store LUN bits in CDB[1] */
 	unsigned unmap_limit_for_ws:1;	/* Use the UNMAP limit for WRITE SAME */
+	unsigned use_rpm_auto:1; /* Enable runtime PM auto suspend */
 
+#define SCSI_DEFAULT_AUTOSUSPEND_DELAY  -1
+	int autosuspend_delay;
 	atomic_t disk_events_disable_depth; /* disable depth for disk events */
 
 	DECLARE_BITMAP(supported_events, SDEV_EVT_MAXBITS); /* supported events */
-- 
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