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Uenal Mutlu
120357ea17
Increasing the SATA/AHCI DMA TX/RX FIFOs (P0DMACR.TXTS and .RXTS, ie. TX_TRANSACTION_SIZE and RX_TRANSACTION_SIZE) from default 0x0 each to 0x3 each, gives a write performance boost of 120 MiB/s to 132 MiB/s from lame 36 MiB/s to 45 MiB/s previously. Read performance is above 200 MiB/s. [tested on SSD using dd bs=4K/8K/12K/16K/20K/24K/32K: peak-perf at 12K] Tested on the SBCs Banana Pi R1 (aka Lamobo R1) and Banana Pi M1 which are based on the Allwinner A20 32bit-SoC (ARMv7-a / arm-linux-gnueabihf). These devices are RaspberryPi-like small devices. This problem of slow SATA write-speed with these small devices lasts for about 7 years now (beginning with the A10 SoC). Many commentators throughout the years wrongly assumed the slow write speed was a hardware limitation. This patch finally solves the problem, which in fact was just a hard-to-find software problem due to lack of SATA/AHCI documentation by the SoC-maker Allwinner Technology. Lists of the affected sunxi and other boards and SoCs with SATA using the ahci_sunxi driver: $ grep -i -e "^&ahci" arch/arm/boot/dts/sun*dts and http://linux-sunxi.org/SATA#Devices_with_SATA_ports See also http://linux-sunxi.org/Category:Devices_with_SATA_port Tested-by: Chen-Yu Tsai <wens@csie.org> Acked-by: Maxime Ripard <maxime.ripard@bootlin.com> Reviewed-by: Hans de Goede <hdegoede@redhat.com> Signed-off-by: Uenal Mutlu <um@mutluit.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.