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authorUenal Mutlu <um@mutluit.com>2019-05-13 16:24:10 +0200
committerJens Axboe <axboe@kernel.dk>2019-07-05 10:17:18 -0600
commit120357ea176e420d313cf8cf2ff35fbe233d3bab (patch)
tree070548efa3eef6a71d91eff1f26c9b3f16815b31 /drivers/ata
parent8756a25b07e6fe878c1a3a40e71a322b18ba57af (diff)
downloadlinux-120357ea176e420d313cf8cf2ff35fbe233d3bab.tar.bz2
drivers: ata: ahci_sunxi: Increased SATA/AHCI DMA TX/RX FIFOs
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>
Diffstat (limited to 'drivers/ata')
-rw-r--r--drivers/ata/ahci_sunxi.c47
1 files changed, 45 insertions, 2 deletions
diff --git a/drivers/ata/ahci_sunxi.c b/drivers/ata/ahci_sunxi.c
index 4100e904376b..cb69b737cb49 100644
--- a/drivers/ata/ahci_sunxi.c
+++ b/drivers/ata/ahci_sunxi.c
@@ -149,8 +149,51 @@ static void ahci_sunxi_start_engine(struct ata_port *ap)
void __iomem *port_mmio = ahci_port_base(ap);
struct ahci_host_priv *hpriv = ap->host->private_data;
- /* Setup DMA before DMA start */
- sunxi_clrsetbits(hpriv->mmio + AHCI_P0DMACR, 0x0000ff00, 0x00004400);
+ /* Setup DMA before DMA start
+ *
+ * NOTE: A similar SoC with SATA/AHCI by Texas Instruments documents
+ * this Vendor Specific Port (P0DMACR, aka PxDMACR) in its
+ * User's Guide document (TMS320C674x/OMAP-L1x Processor
+ * Serial ATA (SATA) Controller, Literature Number: SPRUGJ8C,
+ * March 2011, Chapter 4.33 Port DMA Control Register (P0DMACR),
+ * p.68, https://www.ti.com/lit/ug/sprugj8c/sprugj8c.pdf)
+ * as equivalent to the following struct:
+ *
+ * struct AHCI_P0DMACR_t
+ * {
+ * unsigned TXTS : 4;
+ * unsigned RXTS : 4;
+ * unsigned TXABL : 4;
+ * unsigned RXABL : 4;
+ * unsigned Reserved : 16;
+ * };
+ *
+ * TXTS: Transmit Transaction Size (TX_TRANSACTION_SIZE).
+ * This field defines the DMA transaction size in DWORDs for
+ * transmit (system bus read, device write) operation. [...]
+ *
+ * RXTS: Receive Transaction Size (RX_TRANSACTION_SIZE).
+ * This field defines the Port DMA transaction size in DWORDs
+ * for receive (system bus write, device read) operation. [...]
+ *
+ * TXABL: Transmit Burst Limit.
+ * This field allows software to limit the VBUSP master read
+ * burst size. [...]
+ *
+ * RXABL: Receive Burst Limit.
+ * Allows software to limit the VBUSP master write burst
+ * size. [...]
+ *
+ * Reserved: Reserved.
+ *
+ *
+ * NOTE: According to the above document, the following alternative
+ * to the code below could perhaps be a better option
+ * (or preparation) for possible further improvements later:
+ * sunxi_clrsetbits(hpriv->mmio + AHCI_P0DMACR, 0x0000ffff,
+ * 0x00000033);
+ */
+ sunxi_clrsetbits(hpriv->mmio + AHCI_P0DMACR, 0x0000ffff, 0x00004433);
/* Start DMA */
sunxi_setbits(port_mmio + PORT_CMD, PORT_CMD_START);