+++ /dev/null
-From 120357ea176e420d313cf8cf2ff35fbe233d3bab Mon Sep 17 00:00:00 2001
-From: Uenal Mutlu <um@mutluit.com>
-Date: Mon, 13 May 2019 16:24:10 +0200
-Subject: [PATCH] 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>
----
- drivers/ata/ahci_sunxi.c | 47 ++++++++++++++++++++++++++++++++++++++--
- 1 file changed, 45 insertions(+), 2 deletions(-)
-
---- a/drivers/ata/ahci_sunxi.c
-+++ b/drivers/ata/ahci_sunxi.c
-@@ -157,8 +157,51 @@ static void ahci_sunxi_start_engine(stru
- 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);
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