On Fri, May 18, 2012 at 2:29 AM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > On Thu, 17 May 2012, Lin Ming wrote: > >> Add runtime pm suspend/resume callbacks to request queue. >> As an example, implement these callbacks in sd driver. > > This is not the way to do it. The block subsystem should not use > suspend/resume callbacks. > > Instead, there should be block functions that can be called by client > drivers: block_pre_runtime_suspend, block_post_runtime_suspend, > bock_pre_runtime_resume, and block_post_runtime_resume. > > They should do something like this: > > block_pre_runtime_suspend: > If any requests are in the queue, return -EBUSY. > Otherwise set q->rpm_status to RPM_SUSPENDING and > return 0. > > block_post_runtime_suspend: > If the suspend succeeded then set q->rpm_status to > RPM_SUSPENDED. Otherwise set it to RPM_ACTIVE and > call pm_runtime_mark_last_busy(). > > block_pre_runtime_resume: > Set q->rpm_status to RPM_RESUMING. > > block_post_runtime_resume: > If the resume succeeded then set q->rpm_status to > RPM_ACTIVE and call pm_runtime_mark_last_busy() and > pm_runtime_request_autosuspend(). > Otherwise set q->rpm_status to RPM_SUSPENDED. > > There should also be an initialization function for client drivers to > call. block_runtime_pm_init() should call pm_runtime_mark_last_busy(), > pm_runtime_use_autosuspend(), and pm_runtime_autosuspend(). > > Next, you have to modify the parts of the block layer that run when a > new request is added to the queue or a request is removed. > > When a request is added: > If q->rpm_status is RPM_SUSPENDED, or if q->rpm_status > is RPM_SUSPENDING and the REQ_PM flag isn't set, call > pm_runtime_request_resume(). > > When a request finishes: > Call pm_runtime_mark_last_busy(). > > Next, you have to change the parts of the block layer responsible for > taking a request from the queue and handing it to the lower-level > driver (both peek and get). If q->rpm_status is RPM_SUSPENDED, they > shouldn't do anything -- act as though the queue is empty. If > q->rpm_status is RPM_SUSPENDING or RPM_RESUMING, they should hand over > the request only if it has the REQ_PM flag set. > > For this to work, the block layer has to know what struct device > pointer to pass to the pm_runtime_* routines. You'll have to add that > information to the request_queue structure; I guess q->dev can get set > by block_pm_runtime_init(). In fact, when that's done you won't need > q->rpm_status any more. You'll be able to use c > directly, and you won't have to update it because the PM core does that > for you. > > (Or maybe it would be easier to make q->rpm_status be a pointer to > q->dev->power.rpm_status. That way, if CONFIG_PM_RUNTIME isn't enabled > or block_runtime_pm_init() hasn't been called, you can have > q->rpm_status simply point to a static value that is permanently set to > RPM_ACTIVE.) I think we need q->rpm_status. Block layer check ->rpm_status and client driver set this status. And the status is synchronized with queue's spin lock. If we use q->dev->power.rpm_status then how to sync it between block layer and client driver? Do you mean block layer will need to acquire q->dev->power.lock? Lin Ming > > I may have left some parts out from this brief description. Hopefully > you'll be able to figure out the general idea and get it to work. > > Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
