On Thu, 2012-07-05 at 15:11 +0200, Rafael J. Wysocki wrote: > On Thursday, July 05, 2012, Lin Ming wrote: > > Add runtime pm helper functions: > > > > blk_pm_runtime_init() > > blk_pre_runtime_suspend() > > blk_post_runtime_suspend() > > blk_pre_runtime_resume() > > blk_post_runtime_suspend() > > What exactly do you need these things for? Please be specific. Alan described these functions nicely, copied here. http://marc.info/?l=linux-kernel&m=133727953025955&w=2 I'll add these function descriptions to the patch log. ==== 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 q->dev->power.rpm_status 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 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. ==== Thanks, Lin Ming -- 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
