[U-Boot] [PATCH v2] sunxi: Support booting from SPI flash

[Simon Glass]

Hi,

On 7 June 2016 at 05:28, Siarhei Siamashka <siarhei.siamashka at gmail.com> wrote:
> Allwinner devices support SPI flash as one of the possible
> bootable media type. The SPI flash chip needs to be connected
> to SPI0 pins (port C) to make this work. More information is
> available at:
>
>     https://linux-sunxi.org/Bootable_SPI_flash
>
> This patch adds the initial support for booting from SPI flash.
> The existing SPI frameworks are not used in order to reduce the
> SPL code size. Right now the SPL size grows by ~370 bytes when
> CONFIG_SPL_SPI_SUNXI option is enabled.
>
> While there are no popular Allwinner devices with SPI flash at
> the moment, testing can be done using a SPI flash module (it
> can be bought for ~2$ on ebay) and jumper wires with the boards,
> which expose relevant pins on the expansion header. The SPI flash
> chips themselves are very cheap (some prices are even listed as
> low as 4 cents) and should not cost much if somebody decides to
> design a development board with an SPI flash chip soldered on
> the PCB.
>
> Another nice feature of the SPI flash is that it can be safely
> accessed in a device-independent way (since we know that the
> boot ROM is already probing these pins during the boot time).
> And if, for example, Olimex boards opted to use SPI flash instead
> of EEPROM, then they would have been able to have U-Boot installed
> in the SPI flash now and boot the rest of the system from the SATA
> hard drive. Hopefully we may see new interesting Allwinner based
> development boards in the future, now that the software support
> for the SPI flash is in a better shape :-)
>
> Testing can be done by enabling the CONFIG_SPL_SPI_SUNXI option
> in a board defconfig, then building U-Boot and finally flashing
> the resulting u-boot-sunxi-with-spl.bin binary over USB OTG with
> a help of the sunxi-fel tool:
>
>    sunxi-fel spiflash-write 0 u-boot-sunxi-with-spl.bin
>
> The device needs to be switched into FEL (USB recovery) mode first.
> The most suitable boards for testing are Orange Pi PC and Pine64.
> Because these boards are cheap, have no built-in NAND/eMMC and
> expose SPI0 pins on the Raspberry Pi compatible expansion header.
> The A13-OLinuXino-Micro board also can be used.
>
> Signed-off-by: Siarhei Siamashka <siarhei.siamashka at gmail.com>
> ---
>
> Changes in v2:
>  - Add Kconfig option (CONFIG_SPL_SPI_SUNXI) and move the SPI flash
>    support code into a separate source file
>  - Use CONFIG_SYS_SPI_U_BOOT_OFFS instead of the hardcoded constant
>  - Deinitialize the SPI controller and undo pin muxing after the job
>    is done
>  - Size reduction of the SPI transfer function
>  - Add delay after each SPI transfer to ensure that the chip select
>    deassert timing requirements (tSHSL) are always satisfied
>  - More comments in the code
>
>
>  arch/arm/include/asm/arch-sunxi/gpio.h |   3 +
>  arch/arm/mach-sunxi/board.c            |   5 +
>  common/spl/spl.c                       |   4 +-
>  drivers/mtd/spi/Kconfig                |  12 ++
>  drivers/mtd/spi/Makefile               |   1 +
>  drivers/mtd/spi/sunxi_spi_spl.c        | 283 +++++++++++++++++++++++++++++++++
>  include/configs/sunxi-common.h         |   5 +
>  7 files changed, 311 insertions(+), 2 deletions(-)
>  create mode 100644 drivers/mtd/spi/sunxi_spi_spl.c

Shouldn't this be a normal SPI driver? Then you could put this in
common/spl/spl_spi.c.

Regards,
Simon