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Subject[PATCH v6 2/3] scsi: sd: send REQUEST SENSE for BLIST_MEDIA_CHANGE devices in runtime_resume()
Date
For SD cardreader devices that have the BLIST_MEDIA_CHANGE flag set,
a MEDIA CHANGE unit attention is received after resuming from runtime
suspend. Send a REQUEST SENSE to avoid that.

The "downside" is that for these devices we now rely on users not to
really 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

Signed-off-by: Martin Kepplinger <martin.kepplinger@puri.sm>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
---
drivers/scsi/sd.c | 23 ++++++++++++++++++++++-
1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 6d2d63629a90..34554224b89a 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -63,6 +63,7 @@
#include <scsi/scsi_cmnd.h>
#include <scsi/scsi_dbg.h>
#include <scsi/scsi_device.h>
+#include <scsi/scsi_devinfo.h>
#include <scsi/scsi_driver.h>
#include <scsi/scsi_eh.h>
#include <scsi/scsi_host.h>
@@ -114,6 +115,7 @@ 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);
@@ -608,7 +610,7 @@ 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 = {
@@ -3720,6 +3722,25 @@ 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->sdev_bflags & BLIST_MEDIA_CHANGE) {
+ /* clear the devices' 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).
--
2.30.2
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