scsi: sd: REQUEST SENSE for BLIST_IGN_MEDIA_CHANGE devices in runtime_resume()

For SD card reader devices that have the BLIST_IGN_MEDIA_CHANGE flag
set, a MEDIUM MAY HAVE CHANGED unit attention is established after
resuming from runtime suspend. Send a REQUEST SENSE to consume the UA.

The "downside" is that for these devices we now rely on users to not
change the medium (SD card) *during* a runtime suspend/resume cycle,
i.e. when not unmounting.

To enable runtime PM for an SD cardreader (device number 0:0:0:0), do:

echo 0 > /sys/module/block/parameters/events_dfl_poll_msecs
echo 1000 > /sys/bus/scsi/devices/0:0:0:0/power/autosuspend_delay_ms
echo auto > /sys/bus/scsi/devices/0:0:0:0/power/control

[mkp: use scsi_device flag instead of poking at BLIST]

Link: https://lore.kernel.org/r/20210704075403.147114-3-martin.kepplinger@puri.sm
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin Kepplinger <martin.kepplinger@puri.sm>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index b8d55af763f92ddc62f0ca5d546dd03801a6fc1e..e7ef4728d5eb86bd546f602e021f0d1185a2ccb2 100644 (file)
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -110,6 +110,7 @@ static void sd_shutdown(struct device *);
 static int sd_suspend_system(struct device *);
 static int sd_suspend_runtime(struct device *);
 static int sd_resume(struct device *);
+static int sd_resume_runtime(struct device *);
 static void sd_rescan(struct device *);
 static blk_status_t sd_init_command(struct scsi_cmnd *SCpnt);
 static void sd_uninit_command(struct scsi_cmnd *SCpnt);
@@ -604,7 +605,7 @@ static const struct dev_pm_ops sd_pm_ops = {
        .poweroff               = sd_suspend_system,
        .restore                = sd_resume,
        .runtime_suspend        = sd_suspend_runtime,
-       .runtime_resume         = sd_resume,
+       .runtime_resume         = sd_resume_runtime,
 };
 
 static struct scsi_driver sd_template = {
@@ -3716,6 +3717,25 @@ static int sd_resume(struct device *dev)
        return ret;
 }
 
+static int sd_resume_runtime(struct device *dev)
+{
+       struct scsi_disk *sdkp = dev_get_drvdata(dev);
+       struct scsi_device *sdp = sdkp->device;
+
+       if (sdp->ignore_media_change) {
+               /* clear the device's sense data */
+               static const u8 cmd[10] = { REQUEST_SENSE };
+
+               if (scsi_execute(sdp, cmd, DMA_NONE, NULL, 0, NULL,
+                                NULL, sdp->request_queue->rq_timeout, 1, 0,
+                                RQF_PM, NULL))
+                       sd_printk(KERN_NOTICE, sdkp,
+                                 "Failed to clear sense data\n");
+       }
+
+       return sd_resume(dev);
+}
+
 /**
  *     init_sd - entry point for this driver (both when built in or when
  *     a module).