On Thu, 9 Jun 2016 19:42:55 -0700 Simon Glass sjg@chromium.org wrote:
Hi,
On 9 June 2016 at 18:33, Siarhei Siamashka siarhei.siamashka@gmail.com wrote:
Hi Simon,
On Thu, 9 Jun 2016 17:36:10 -0700 Simon Glass sjg@chromium.org wrote:
Hi,
On 7 June 2016 at 05:28, Siarhei Siamashka siarhei.siamashka@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_flashThis 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@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.
This source file contains both a sunxi SPI controller support and a basic SPI flash read functionality glued together for size reduction purposes.
We are interested in implementing the "spl_spi_load_image()" function, because this is what gets called when handling the BOOT_DEVICE_SPI case.
The "drivers/mtd/spi" directory contains the "spi_spl_load.c" file, which implements this particular function with the help of the generic SPI flash support code from "spi_flash.c" and the generic SPI bus support provided by the code from the "drivers/spi" directory.
What I'm doing in this patch is an implementation of a size reduced sunxi-specific replacement for "spi_spl_load.c". But in U-Boot proper (where the code size is not a problem anymore) we will need a real sunxi SPI driver.
OK I see, fair enough.
Do you know how much space this saves? I'm actually not sure how much overhead the SPI flash layer adds.
I don't have a DM based SPI driver for sunxi yet. But I tried to disable SPI flash on some other boards and check the SPL size reduction. I don't remember what kind of board it was before, but the size was reduced by several kilobytes. Now tried it again with the "spring_defconfig" build:
== normal build ==
text data bss dec hex filename 11796 1260 0 13056 3300 spl/u-boot-spl
== spi flash disabled ==
text data bss dec hex filename 6812 1052 0 7864 1eb8 spl/u-boot-spl
My changes in "include/configs/exynos5-dt-common.h" to disable SPI flash:
-#define CONFIG_ENV_IS_IN_SPI_FLASH +#define CONFIG_ENV_IS_IN_MMC +/* #define CONFIG_ENV_SPI_BASE 0x12D30000 #define FLASH_SIZE (4 << 20) #define CONFIG_ENV_OFFSET (FLASH_SIZE - CONFIG_ENV_SECT_SIZE) #define CONFIG_SPI_BOOTING +*/
Yes, this was not a very clean experiment. But still ~5K looks significantly larger than ~400 bytes.
For comparison, building "Cubieboard_defconfig" from the current master branch (6b3943f1b04be60f147ee540fbd72c4c7ea89f80) results in the following SPL sizes, depending on the GCC version:
=== GCC 4.7 === text data bss dec hex filename 21743 640 256 22639 586f spl/u-boot-spl
=== GCC 4.9 === text data bss dec hex filename 21667 640 256 22563 5823 spl/u-boot-spl
=== GCC 5.3 === text data bss dec hex filename 21571 640 256 22467 57c3 spl/u-boot-spl
=== GCC 6.1 === text data bss dec hex filename 18406 640 256 19302 4b66 spl/u-boot-spl
Please note that NAND and FIT are still not enabled, though CONFIG_USE_TINY_PRINTF is not enabled either. And 24 KiB is the size limit for the SPL, enforced by the boot ROM.