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 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 <[email protected]>
---
drivers/scsi/sd.c | 37 ++++++++++++++++++++++++++++++++++++-
1 file changed, 36 insertions(+), 1 deletion(-)
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 6d2d63629a90..0acc732f1933 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 +3722,39 @@ 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;
+ int timeout, retries, res;
+ struct scsi_sense_hdr my_sshdr;
+
+ if (!sdkp) /* E.g.: runtime resume at the start of sd_probe() */
+ return 0;
+
+ sdp = sdkp->device;
+ timeout = sdp->request_queue->rq_timeout * SD_FLUSH_TIMEOUT_MULTIPLIER;
+
+ if (sdp->sdev_bflags & BLIST_MEDIA_CHANGE) {
+ for (retries = 3; retries > 0; --retries) {
+ unsigned char cmd[10] = { 0 };
+
+ cmd[0] = REQUEST_SENSE;
+ /*
+ * Leave the rest of the command zero to indicate
+ * flush everything.
+ */
+ res = scsi_execute(sdp, cmd, DMA_NONE, NULL, 0, NULL,
+ &my_sshdr, timeout,
+ sdkp->max_retries, 0, RQF_PM, NULL);
+ if (res == 0)
+ break;
+ }
+ }
+
+ return sd_resume(dev);
+}
+
/**
* init_sd - entry point for this driver (both when built in or when
* a module).
--
2.30.2
On 6/28/21 6:34 AM, Martin Kepplinger wrote:
> +static int sd_resume_runtime(struct device *dev)
> +{
> + struct scsi_disk *sdkp = dev_get_drvdata(dev);
> + struct scsi_device *sdp;
> + int timeout, retries, res;
> + struct scsi_sense_hdr my_sshdr;
Since the sense data is ignored, consider removing the "my_sshdr"
declaration and passing NULL as sense pointer to scsi_execute().
> + if (!sdkp) /* E.g.: runtime resume at the start of sd_probe() */
> + return 0;
Are you sure that this code is necessary? There is an
scsi_autopm_get_device(sdp) call at the start of sd_probe() and
scsi_autopm_put_device(sdp) call at the end of sd_probe(). In other
words, no runtime suspend will happen between the
device_initialize(&sdkp->dev) call in sd_probe() and the
dev_set_drvdata(dev, sdkp) call in the same function.
> + if (sdp->sdev_bflags & BLIST_MEDIA_CHANGE) {
> + for (retries = 3; retries > 0; --retries) {
> + unsigned char cmd[10] = { 0 };
> +
> + cmd[0] = REQUEST_SENSE;
Please define the CDB as follows:
static const u8 cmd[10] = { REQUEST_SENSE };
> + /*
> + * Leave the rest of the command zero to indicate
> + * flush everything.
> + */
Shouldn't this comment appear above the CDB definition? Also, what does
"flush everything" mean? According to SPC sense data is discarded from
the device while processing REQUEST SENSE, no matter what the value of
the ALLOCATION LENGTH parameter in that command is. From SPC-6: "the
REQUEST SENSE command with any allocation length clears the sense data."
> + res = scsi_execute(sdp, cmd, DMA_NONE, NULL, 0, NULL,
> + &my_sshdr, timeout,
> + sdkp->max_retries, 0, RQF_PM, NULL);
Only one level of retries please. Can sdkp->max_retries be changed into 1?
Thanks,
Bart.