linux-kernel - Re: [PATCH v3] drivers: ata: ahci_sunxi: Increased SATA/AHCI DMA TX/RX FIFOs

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Message-ID: <95b399ff-86ef-134b-7c55-d4205cbe9eed@kernel.dk>
Date:   Fri, 5 Jul 2019 10:17:48 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Uenal Mutlu <um@...luit.com>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Chen-Yu Tsai <wens@...e.org>, linux-ide@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:     linux-sunxi@...glegroups.com, linux-amarula@...rulasolutions.com,
        Jagan Teki <jagan@...rulasolutions.com>,
        Pablo Greco <pgreco@...tosproject.org>,
        Mark Rutland <mark.rutland@....com>,
        Oliver Schinagl <oliver@...inagl.nl>,
        Linus Walleij <linus.walleij@...aro.org>,
        Hans de Goede <hdegoede@...hat.com>,
        FUKAUMI Naoki <naobsd@...il.com>,
        Andre Przywara <andre.przywara@....com>,
        Stefan Monnier <monnier@....umontreal.ca>
Subject: Re: [PATCH v3] drivers: ata: ahci_sunxi: Increased SATA/AHCI DMA
 TX/RX FIFOs

On 5/13/19 8:24 AM, 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 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

Applied for 5.3, thanks.

-- 
Jens Axboe