Add notes about the new sd sysfs knob that works around problems with runtime PM for certain types of SD cardreaders. Signed-off-by: Martin Kepplinger <martin.kepplinger@xxxxxxx> --- Documentation/scsi/sd-parameters.rst | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/Documentation/scsi/sd-parameters.rst b/Documentation/scsi/sd-parameters.rst index 87d554008bfb..a77b9fdffddf 100644 --- a/Documentation/scsi/sd-parameters.rst +++ b/Documentation/scsi/sd-parameters.rst @@ -25,3 +25,17 @@ To modify the caching mode without making the change persistent, prepend "temporary " to the cache type string. E.g.:: # echo "temporary write back" > cache_type + +ignore_resume_medium_changed (RW) +--------------------------------- +Some SD cardreaders deliver a "media changed" unit attention (that results +in I/O error) when they are resumed from suspend. This prevents users +to use runtime PM with these devices. To enable runtime PM for an SD +cardreader (here, device number 0:0:0:0), do something like: + +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 + +And if using the mounted disk filesystem causes trouble, try setting +ignore_resume_medium_changed to 1. -- 2.20.1
