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248 lines
7.7 KiB
Plaintext
248 lines
7.7 KiB
Plaintext
#
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# Copyright (C) 2015 Google. Inc
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# Written by Simon Glass <sjg@chromium.org>
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#
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# SPDX-License-Identifier: GPL-2.0+
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#
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U-Boot on Rockchip
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==================
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There are several repositories available with versions of U-Boot that support
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many Rockchip devices [1] [2].
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The current mainline support is experimental only and is not useful for
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anything. It should provide a base on which to build.
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So far only support for the RK3288 is provided.
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Prerequisites
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=============
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You will need:
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- Firefly RK3288 baord
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- Power connection to 5V using the supplied micro-USB power cable
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- Separate USB serial cable attached to your computer and the Firefly
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(connect to the micro-USB connector below the logo)
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- rkflashtool [3]
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- openssl (sudo apt-get install openssl)
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- Serial UART connection [4]
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- Suitable ARM cross compiler, e.g.:
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sudo apt-get install gcc-4.7-arm-linux-gnueabi
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Building
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========
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At present three RK3288 boards are supported:
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- Firefly RK3288 - use firefly-rk3288 configuration
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- Radxa Rock 2 - also uses firefly-rk3288 configuration
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- Haier Chromebook - use chromebook_jerry configuration
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For example:
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CROSS_COMPILE=arm-linux-gnueabi- make O=firefly firefly-rk3288_defconfig all
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(or you can use another cross compiler if you prefer)
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Note that the Radxa Rock 2 uses the Firefly configuration for now as
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device tree files are not yet available for the Rock 2. Clearly the two
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have hardware differences, so this approach will break down as more drivers
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are added.
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Writing to the board with USB
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=============================
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For USB to work you must get your board into ROM boot mode, either by erasing
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your MMC or (perhaps) holding the recovery button when you boot the board.
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To erase your MMC, you can boot into Linux and type (as root)
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dd if=/dev/zero of=/dev/mmcblk0 bs=1M
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Connect your board's OTG port to your computer.
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To create a suitable image and write it to the board:
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./firefly-rk3288/tools/mkimage -T rkimage -d \
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./firefly-rk3288/spl/u-boot-spl-dtb.bin out && \
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cat out | openssl rc4 -K 7c4e0304550509072d2c7b38170d1711 | rkflashtool l
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If all goes well you should something like:
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U-Boot SPL 2015.07-rc1-00383-ge345740-dirty (Jun 03 2015 - 10:06:49)
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Card did not respond to voltage select!
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spl: mmc init failed with error: -17
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### ERROR ### Please RESET the board ###
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You will need to reset the board before each time you try. Yes, that's all
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it does so far. If support for the Rockchip USB protocol or DFU were added
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in SPL then we could in principle load U-Boot and boot to a prompt from USB
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as several other platforms do. However it does not seem to be possible to
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use the existing boot ROM code from SPL.
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Booting from an SD card
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=======================
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To write an image that boots from an SD card (assumed to be /dev/sdc):
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./firefly-rk3288/tools/mkimage -T rksd -d \
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firefly-rk3288/spl/u-boot-spl-dtb.bin out && \
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sudo dd if=out of=/dev/sdc seek=64 && \
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sudo dd if=firefly-rk3288/u-boot-dtb.img of=/dev/sdc seek=256
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This puts the Rockchip header and SPL image first and then places the U-Boot
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image at block 256 (i.e. 128KB from the start of the SD card). This
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corresponds with this setting in U-Boot:
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#define CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR 256
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Put this SD (or micro-SD) card into your board and reset it. You should see
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something like:
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U-Boot SPL 2015.07-rc1-00383-ge345740-dirty (Jun 03 2015 - 11:04:40)
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U-Boot 2015.07-rc1-00383-ge345740-dirty (Jun 03 2015 - 11:04:40)
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DRAM: 2 GiB
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MMC:
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Using default environment
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In: serial@ff690000
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Out: serial@ff690000
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Err: serial@ff690000
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=>
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Booting from SPI
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================
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To write an image that boots from SPI flash (e.g. for the Haier Chromebook):
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./chromebook_jerry/tools/mkimage -T rkspi -d chromebook_jerry/spl/u-boot-spl-dtb.bin out
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dd if=spl.bin of=out.bin bs=128K conv=sync
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cat chromebook_jerry/u-boot-dtb.img out.bin
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dd if=out.bin of=out.bin.pad bs=4M conv=sync
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This converts the SPL image to the required SPI format by adding the Rockchip
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header and skipping every 2KB block. Then the U-Boot image is written at
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offset 128KB and the whole image is padded to 4MB which is the SPI flash size.
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The position of U-Boot is controlled with this setting in U-Boot:
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#define CONFIG_SYS_SPI_U_BOOT_OFFS (128 << 10)
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If you have a Dediprog em100pro connected then you can write the image with:
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sudo em100 -s -c GD25LQ32 -d out.bin.pad -r
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When booting you should see something like:
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U-Boot SPL 2015.07-rc2-00215-g9a58220-dirty (Jun 23 2015 - 12:11:32)
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U-Boot 2015.07-rc2-00215-g9a58220-dirty (Jun 23 2015 - 12:11:32 -0600)
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Model: Google Jerry
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DRAM: 2 GiB
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MMC:
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Using default environment
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In: serial@ff690000
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Out: serial@ff690000
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Err: serial@ff690000
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=>
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Future work
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===========
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Immediate priorities are:
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- GPIO (driver exists but is lightly tested)
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- I2C (driver exists but is non-functional)
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- USB host
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- USB device
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- PMIC and regulators (only ACT8846 is supported at present)
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- LCD and HDMI
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- Run CPU at full speed
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- Ethernet
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- NAND flash
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- Support for other Rockchip parts
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- Boot U-Boot proper over USB OTG (at present only SPL works)
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Development Notes
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=================
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There are plenty of patches in the links below to help with this work.
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[1] https://github.com/rkchrome/uboot.git
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[2] https://github.com/linux-rockchip/u-boot-rockchip.git branch u-boot-rk3288
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[3] https://github.com/linux-rockchip/rkflashtool.git
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[4] http://wiki.t-firefly.com/index.php/Firefly-RK3288/Serial_debug/en
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rkimage
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-------
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rkimage.c produces an SPL image suitable for sending directly to the boot ROM
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over USB OTG. This is a very simple format - just the string RK32 (as 4 bytes)
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followed by u-boot-spl-dtb.bin.
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The boot ROM loads image to 0xff704000 which is in the internal SRAM. The SRAM
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starts at 0xff700000 and extends to 0xff718000 where we put the stack.
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rksd
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----
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rksd.c produces an image consisting of 32KB of empty space, a header and
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u-boot-spl-dtb.bin. The header is defined by 'struct header0_info' although
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most of the fields are unused by U-Boot. We just need to specify the
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signature, a flag and the block offset and size of the SPL image.
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The header occupies a single block but we pad it out to 4 blocks. The header
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is encoding using RC4 with the key 7c4e0304550509072d2c7b38170d1711. The SPL
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image can be encoded too but we don't do that.
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The maximum size of u-boot-spl-dtb.bin which the boot ROM will read is 32KB,
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or 0x40 blocks. This is a severe and annoying limitation. There may be a way
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around this limitation, since there is plenty of SRAM, but at present the
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board refuses to boot if this limit is exceeded.
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The image produced is padded up to a block boundary (512 bytes). It should be
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written to the start of an SD card using dd.
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Since this image is set to load U-Boot from the SD card at block offset,
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CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR, dd should be used to write
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u-boot-dtb.img to the SD card at that offset. See above for instructions.
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rkspi
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-----
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rkspi.c produces an image consisting of a header and u-boot-spl-dtb.bin. The
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resulting image is then spread out so that only the first 2KB of each 4KB
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sector is used. The header is the same as with rksd and the maximum size is
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also 32KB (before spreading). The image should be written to the start of
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SPI flash.
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See above for instructions on how to write a SPI image.
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Device tree and driver model
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----------------------------
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Where possible driver model is used to provide a structure to the
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functionality. Device tree is used for configuration. However these have an
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overhead and in SPL with a 32KB size limit some shortcuts have been taken.
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In general all Rockchip drivers should use these features, with SPL-specific
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modifications where required.
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--
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Simon Glass <sjg@chromium.org>
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24 June 2015
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