On 8/17/23 17:19, Bao D. Nguyen wrote:
For example, in SDB mode, after the probe and you want to enable auto-hibern8, you would call ufshcd_auto_hibern8_update() which then calls ufshcd_update_preserves_write_order(). Before auto-hibern8 is enabled, you would check this condition: if (blk_queue_is_zoned(q) && !q->elevator) In other words, auto-hibern8 is enabled only if the above condition false. However, the during a normal operation, the ufshcd_auto_hibern8_update() may not get called at all, and auto-hibern8 can be enabled in SDB mode as part of ufs init. Would that be a problem to have auto-hibern8 enabled without checking whether the above condition is false?
Hi Bao, Probing the host controller happens as follows: * The host controller probing function is called, e.g. ufs_qcom_probe(). * ufshcd_alloc_host() and ufshcd_init() are called directly or indirectly by the host controller probe function. * ufshcd_init() calls scsi_add_host() and async_schedule(ufshcd_async_scan, hba). Once ufshcd_async_scan() is called asynchronously, it performs the following actions: * ufs_probe_hba() is called. This function calls ufshcd_link_startup() indirectly. That function invokes the link_startup_notify vop if it has been defined. Some host drivers set hba->ahit from inside that vop. * scsi_scan_host() is called and calls scsi_alloc_sdev() indirectly. * scsi_alloc_sdev() calls blk_mq_init_queue() and shost->hostt->slave_alloc(). * scsi_add_lun() calls sdev->host->hostt->slave_configure(). * scsi_add_lun() calls scsi_sysfs_add_sdev(). This indirectly causes sd_probe() to be called asynchronously. * sd_probe() calls sd_revalidate_disk(). This results in an indirect call of disk_set_zoned(). Additionally, the ELEVATOR_F_ZBD_SEQ_WRITE flag is set by the sd driver if q->limits.driver_preserves_write_order has not been set. * Still from inside sd_probe(), device_add_disk() is called and a scheduler is selected based on the value of q->required_elevator_features. There are two ways in which host drivers initialize auto-hibernation: * Either by setting hba->ahit before ufshcd_init() is called. * Or by calling ufshcd_auto_hibern8_update() from the link_startup_notify vop. I think the above shows that the zoned model is queried *after* the above methods for enabling auto-hibernation have completed and hence that blk_queue_is_zoned() evaluates to false if a host driver calls ufshcd_auto_hibern8_update() from inside the link_startup_notify vop. If auto-hibernation is enabled from inside the host driver then that should happen before sd_probe() is called. sd_probe() will use the value of q->limits.driver_preserves_write_order that has been set by ufshcd_slave_configure() so there is no risk for inconsistencies between the auto-hibernation configuration and the request queue configuration. Bart.
