On Thu, 2020-05-07 at 18:34 -0700, Randy Dunlap wrote: > Hi, > > On 5/4/20 7:20 AM, [email protected] wrote: > > diff --git a/drivers/scsi/ufs/Kconfig b/drivers/scsi/ufs/Kconfig > > index e2005aeddc2d..0224f224a641 100644 > > --- a/drivers/scsi/ufs/Kconfig > > +++ b/drivers/scsi/ufs/Kconfig > > @@ -160,3 +160,65 @@ config SCSI_UFS_BSG > > > > Select this if you need a bsg device node for your UFS > > controller. > > If unsure, say N. > > + > > +config SCSI_UFSHPB > > + bool "UFS Host Performance Booster (EXPERIMENTAL)" > > + depends on SCSI_UFSHCD > > + help > > + NAND flash-based storage devices, including UFS, have > > mechanisms to > > + translate logical addresses of the IO requests to the > > corresponding > > + physical addresses of the flash storage. Traditionally, this > > L2P > > + mapping data is loaded to the internal SRAM in the storage > > controller. > > + When the capacity of storage is larger, a larger size of SRAM > > for the > > + L2P map data is required. Since increased SRAM size affects > > the > > + manufacturing cost significantly, it is not cost-effective to > > allocate > > + all the amount of SRAM needed to keep all the Logical-address > > to > > + Physical-address (L2P) map data. Therefore, L2P map data, > > which is > > + required to identify the physical address for the requested > > IOs, can > > + only be partially stored in SRAM from NAND flash. Due to this > > partial > > + loading, accessing the flash address area where the L2P > > information > > + for that address is not loaded in the SRAM can result in > > serious > > + performance degradation. > > + > > + UFS Host Performance Booster (HPB) is a software solution for > > the > > + above problem, which uses the host side system memory as a > > cache for > > + the FTL L2P mapping table. It does not need additional > > hardware > > + support from the host side. By using HPB, the L2P mapping > > table can be > > + read from host memory and stored in host-side memory. when > > performing > > Should that be: from device memory and stored in host-side memory. > ? > > Also, s/when/When/ > > > > + the read operation, the corresponding L2P information will be > > sent to > > + the UFS device along with the reading request. Since the L2P > > entry is > > s/reading/read/ > > > + provided in the read request, UFS device does not have to > > load L2P > > + entry from flash memory to UFS internal SRAM. This will > > significantly > > + improve the read performance. > > + > > + When selected, this feature will be built in the UFS driver. > > + > > + If in doubt, say N. > > + > > +config UFSHPB_MAX_MEM_SIZE > > + int "UFS HPB maximum memory size per controller (in MiB)" > > + depends on SCSI_UFSHPB > > + default 128 > > + range 0 65536 > > + help > > + This parameter defines the maximum UFS HPB memory/cache size > > in the > > + host system. The recommended HPB cache size by the UFS device > > can be > > + calculated from bHPBRegionSize and > > wDeviceMaxActiveHPBRegions. The > > + reference formula can be > > s/can be/is/ > > > + > > + (bHPBRegionSize(in KB) / 4KB) * 8 * > > wDeviceMaxActiveHPBRegions. > > + > > + The HPB cache in the host system is used to contain L2P > > mapping > > + entries. If the allocated HPB cache size is lower than what > > calculated > > than that > > > + by the above formula, the use of HPB feature may provide > > lower > > + performance advantage. But the system memory resource has the > > + limitation, we can not let HPB driver allocate its cache at > > will > > + according to the UFS device recommendation, so an appropriate > > size of > > + the cache for HPB should be specified before you choose to > > use HPB, > > + then please enter a non-zero positive integer value. > > + > > + Nevertheless, if you want to leave this to the HPB driver, > > and let the > > + HPB driver allocate the HPB cache based on the recommendation > > of the > > + UFS device. Just give 0 value to this parameter. > > + > > + Leave the default value if unsure. > > thanks.
Hi Randy Thanks for your review. I will change them based on your comments. thanks, Bean
