Implement Host Performance Buffer (HPB) initialization and add function
calls to UFS core driver.

NAND flash-based storage devices, including UFS, have mechanisms to
translate logical addresses of I/O requests to the corresponding physical
addresses of the flash storage.  In UFS, logical-to-physical-address (L2P)
map data, which is required to identify the physical address for the
requested I/Os, 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.

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. The HPB read command allows to
read data faster than a regular read command in UFS since it provides the
physical address (HPB Entry) of the desired logical block in addition to
its logical address. The UFS device can access the physical block in NAND
directly without searching and uploading L2P mapping table. This improves
read performance because the NAND read operation for uploading L2P mapping
table is removed.

In HPB initialization, the host checks if the UFS device supports HPB
feature and retrieves related device capabilities. Then, HPB parameters are
configured in the device.

Total start-up time of popular applications was measured and the difference
observed between HPB being enabled and disabled. Popular applications are
12 game apps and 24 non-game apps. Each test cycle consists of running 36
applications in sequence. We repeated the cycle for observing performance
improvement by L2P mapping cache hit in HPB.

The following is the test environment:

 - kernel version: 4.4.0
 - RAM: 8GB
 - UFS 2.1 (64GB)

Results:

   +-------+----------+----------+-------+
   | cycle | baseline | with HPB | diff  |
   +-------+----------+----------+-------+
   | 1     | 272.4    | 264.9    | -7.5  |
   | 2     | 250.4    | 248.2    | -2.2  |
   | 3     | 226.2    | 215.6    | -10.6 |
   | 4     | 230.6    | 214.8    | -15.8 |
   | 5     | 232.0    | 218.1    | -13.9 |
   | 6     | 231.9    | 212.6    | -19.3 |
   +-------+----------+----------+-------+

We also measured HPB performance using iozone:

   $ iozone -r 4k -+n -i2 -ecI -t 16 -l 16 -u 16 -s $IO_RANGE/16 -F \
   mnt/tmp_1 mnt/tmp_2 mnt/tmp_3 mnt/tmp_4 mnt/tmp_5 mnt/tmp_6 mnt/tmp_7 \
   mnt/tmp_8 mnt/tmp_9 mnt/tmp_10 mnt/tmp_11 mnt/tmp_12 mnt/tmp_13 \
   mnt/tmp_14 mnt/tmp_15 mnt/tmp_16

Results:

   +----------+--------+---------+
   | IO range | HPB on | HPB off |
   +----------+--------+---------+
   |   1 GB   | 294.8  | 300.87  |
   |   4 GB   | 293.51 | 179.35  |
   |   8 GB   | 294.85 | 162.52  |
   |  16 GB   | 293.45 | 156.26  |
   |  32 GB   | 277.4  | 153.25  |
   +----------+--------+---------+

Link: https://lore.kernel.org/r/20210712085830epcms2p8c1288b7f7a81b044158a18232617b572@epcms2p8Reported-by: kernel test robot <lkp@intel.com>
Tested-by: Bean Huo <beanhuo@micron.com>
Tested-by: Can Guo <cang@codeaurora.org>
Tested-by: Stanley Chu <stanley.chu@mediatek.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Can Guo <cang@codeaurora.org>
Reviewed-by: Bean Huo <beanhuo@micron.com>
Reviewed-by: Stanley Chu <stanley.chu@mediatek.com>
Acked-by: Avri Altman <Avri.Altman@wdc.com>
Signed-off-by: Daejun Park <daejun7.park@samsung.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>