NAND flash-based storage devices, needs to translate the logical addresses of the IO requests to its corresponding physical addresses of the flash storage. As the internal SRAM of the storage device cannot accommodate the entire L2P mapping table, the device can only partially load the L2P data it needs based on the incoming LBAs. As a result, cache misses - which are more frequent in random read access, can result in serious performance degradation. To remedy the above, UFS3.1 offers the Host Performance Booster (HPB) feature, which uses the host’s system memory as a cache for L2P map data. The basic concept of HPB is to cache L2P mapping entries in host system memory so that both physical block address (PBA) and logical block address (LBA) can be delivered in HPB read command. Not to be confused with host-managed-FTL, HPB is merely about NAND flash cost reduction. HPB, by its nature, imposes an interesting question regarding the proper location of its components across the storage stack. On Init it requires to detect the HPB capabilities and parameters, which can be only done from the LLD level. On the other hand, it requires to send scsi commands as part of its cache management, which preferably should be done from scsi mid-layer, and compose the "HPB_READ" command, which should be done as part of scsi command setup path. Therefore, we came up with a 2 module layout: ufshpb in the ufs driver, and scsi_dh_ufshpb under scsi device handler. The ufshpb module bear 2 main duties. During initialization, it reads the hpb configuration from the device. Later on, during the scan host phase, it attaches the scsi device and activates the scsi hpb device handler. The second duty mainly concern supporting the HPB cache management. The scsi hpb device handler will perform the cache management and send the HPB_READ command. The modules will communicate via the standard device handler API: the handler_data opaque pointer, and the set_params op-mode. This series has borrowed heavily from a HPB implementation that was published as part of the pixel3 code, authored by: Yongmyung Lee <ymhungry.lee@xxxxxxxxxxx> and Jinyoung Choi <j-young.choi@xxxxxxxxxxx>. We kept some of its design and implementation details. We made some minor modifications to adopt the latest spec changes (HPB1.0 was not close when the driver initially published), and also divide the implementation between the scsi handler and the ufs modules, instead of a single module in the original driver, which simplified the implementation to a great deal and resulted in far less code. One more big difference is that the Pixel3 driver support device managed mode, while we are supporting host managed mode, which reflect heavily on the cache management decision process. Many thanks to Damien Le Moal for his insightful comments. Avri Altman (13): scsi: ufs: Add HPB parameters scsi: ufshpb: Init part I - Read HPB config scsi: scsi_dh: Introduce scsi_dh_ufshpb scsi: ufs: ufshpb: Init part II - Attach scsi device scsi: ufs: ufshpb: Disable HPB if no HPB-enabled luns scsi: scsi_dh: ufshpb: Prepare for L2P cache management scsi: scsi_dh: ufshpb: Add ufshpb state machine scsi: dh: ufshpb: Activate pinned regions scsi: ufshpb: Add response API scsi: dh: ufshpb: Add ufshpb_set_params scsi: Allow device handler set their own CDB scsi: dh: ufshpb: Add prep_fn handler scsi: scsi_dh: ufshpb: Add "Cold" subregions timer drivers/scsi/device_handler/Makefile | 1 + drivers/scsi/device_handler/scsi_dh_ufshpb.c | 1480 ++++++++++++++++++++++++++ drivers/scsi/scsi_lib.c | 5 +- drivers/scsi/sd.c | 9 + drivers/scsi/ufs/Kconfig | 13 + drivers/scsi/ufs/Makefile | 1 + drivers/scsi/ufs/ufs.h | 16 + drivers/scsi/ufs/ufshcd.c | 12 + drivers/scsi/ufs/ufshcd.h | 11 + drivers/scsi/ufs/ufshpb.c | 610 +++++++++++ drivers/scsi/ufs/ufshpb.h | 28 + include/scsi/scsi_dh_ufshpb.h | 67 ++ 12 files changed, 2251 insertions(+), 2 deletions(-) create mode 100644 drivers/scsi/device_handler/scsi_dh_ufshpb.c create mode 100644 drivers/scsi/ufs/ufshpb.c create mode 100644 drivers/scsi/ufs/ufshpb.h create mode 100644 include/scsi/scsi_dh_ufshpb.h -- 2.7.4
