Re: [RFC PATCH v2 RESEND] drivers: ata: ahci_sunxi: Increased SATA/AHCI DMA TX/RX FIFOs

[U.Mutlu]

Maxime Ripard wrote on 05/13/2019 11:59 AM:
> On Sun, May 12, 2019 at 10:59:54PM +0200, Uenal Mutlu wrote:
> > 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 about 200 MiB/s.
> > [tested on SSD using dd bs=2K/4K/8K/12K/16K/24K/32K: peak-perf at 12K].
> >
> > Tested on the Banana Pi R1 (aka Lamobo R1) and Banana Pi M1 SBCs
> > with Allwinner A20 32bit-SoCs (ARMv7-a / arm-linux-gnueabihf).
> > These devices are RaspberryPi-like small devices.
> >
> > This problem of slow SATA write-speed with these small devices lasts now
> > for more than 5 years. 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-fix software problem
> > (b/c of lack of documentation by the SoC-maker Allwinner Technology).
> >
> > RFC: Since more than about 25 similar SBC/SoC models do use the
> > ahci_sunxi driver, users are encouraged to test it on all the
> > affected boards and give feedback.
> >
> > 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
> >
> > Patch v2:
> >    - Commented the patch in-place in ahci_sunxi.c
> >    - With bs=12K and no conv=... passed to dd, the write performance
> >      rises further to 132 MiB/s
> >    - Changed MB/s to MiB/s
> >    - Posted the story behind the patch:
> >      http://lkml.iu.edu/hypermail/linux/kernel/1905.1/03506.html
> >    - Posted a dd test script to find optimal bs, and some results:
> >      https://bit.ly/2YoOzEM
> >
> > Patch v1:
> >    - States bs=4K for dd and a write performance of 120 MiB/s
> >
> > Signed-off-by: Uenal Mutlu <um@xxxxxxxxxxx>
>
> Acked-by: Maxime Ripard <maxime.ripard@xxxxxxxxxxx>

Thx!

> Just a minor nitpick though, the part starting with RFC: and with the
> version changelog should be after the --- below so that it doesn't get
> applied as part of the commit log.

Ok, I'll do it better in the future.
Thx again.


> Maxime
>
> --
> Maxime Ripard, Bootlin
> Embedded Linux and Kernel engineering
> https://bootlin.com