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40f4839ce1
Check for bmode before reading the boot device to check if a serial downloader is started, and returns UART if the serial downloader is set, letting SPL to wait for an image if CONFIG_SPL_YMODEM_SUPPORT is set. This allows to load again a SPL based board with imx_usb_loader together with a tool such as kermit. Signed-off-by: Stefano Babic <sbabic@denx.de> CC: Tim Harvey <tharvey@gateworks.com> CC: Fabio Estevam <Fabio.Estevam@freescale.com> CC: Eric Nelson <eric.nelson@boundarydevices.com> Reviewed-by: Eric Nelson <eric@nelint.com> Tested-by: Eric Nelson <eric@nelint.com>
138 lines
3.6 KiB
Plaintext
138 lines
3.6 KiB
Plaintext
U-Boot for Freescale i.MX6
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This file contains information for the port of U-Boot to the Freescale i.MX6
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SoC.
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1. CONVENTIONS FOR FUSE ASSIGNMENTS
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-----------------------------------
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1.1 MAC Address: It is stored in fuse bank 4, with the 32 lsbs in word 2 and the
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16 msbs in word 3.
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Example:
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For reading the MAC address fuses on a MX6Q:
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- The MAC address is stored in two fuse addresses (the fuse addresses are
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described in the Fusemap Descriptions table from the mx6q Reference Manual):
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0x620[31:0] - MAC_ADDR[31:0]
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0x630[15:0] - MAC_ADDR[47:32]
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In order to use the fuse API, we need to pass the bank and word values, which
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are calculated as below:
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Fuse address for the lower MAC address: 0x620
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Base address for the fuses: 0x400
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(0x620 - 0x400)/0x10 = 0x22 = 34 decimal
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As the fuses are arranged in banks of 8 words:
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34 / 8 = 4 and the remainder is 2, so in this case:
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bank = 4
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word = 2
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And the U-boot command would be:
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=> fuse read 4 2
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Reading bank 4:
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Word 0x00000002: 9f027772
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Doing the same for the upper MAC address:
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Fuse address for the upper MAC address: 0x630
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Base address for the fuses: 0x400
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(0x630 - 0x400)/0x10 = 0x23 = 35 decimal
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As the fuses are arranged in banks of 8 words:
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35 / 8 = 4 and the remainder is 3, so in this case:
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bank = 4
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word = 3
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And the U-boot command would be:
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=> fuse read 4 3
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Reading bank 4:
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Word 0x00000003: 00000004
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,which matches the ethaddr value:
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=> echo ${ethaddr}
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00:04:9f:02:77:72
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Some other useful hints:
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- The 'bank' and 'word' numbers can be easily obtained from the mx6 Reference
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Manual. For the mx6quad case, please check the "46.5 OCOTP Memory Map/Register
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Definition" from the "i.MX 6Dual/6Quad Applications Processor Reference Manual,
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Rev. 1, 04/2013" document. For example, for the MAC fuses we have:
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Address:
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21B_C620 Value of OTP Bank4 Word2 (MAC Address)(OCOTP_MAC0)
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21B_C630 Value of OTP Bank4 Word3 (MAC Address)(OCOTP_MAC1)
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- The command '=> fuse read 4 2 2' reads the whole MAC addresses at once:
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=> fuse read 4 2 2
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Reading bank 4:
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Word 0x00000002: 9f027772 00000004
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2. Using imx_usb_loader for first install with SPL
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--------------------------------------------------
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imx_usb_loader is a very nice tool by BoundaryDevice that
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allow to install U-Boot without a JTAG debugger, using
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the USB boot mode as described in the manual. It is
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a replacement for Freescale's MFGTOOLS.
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The sources can be found here:
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https://github.com/boundarydevices/imx_usb_loader.git
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Booting in USB mode, the i.MX6 announces itself to the Linux Host as:
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Bus 001 Device 111: ID 15a2:0061 Freescale Semiconductor, Inc.
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imx_usb_loader is able to download a single file (u-boot.imx)
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to the board. For boards without SPL support, it is enough to
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issue the command:
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sudo ../imx_usb_loader/imx_usb -v u-boot.imx
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Getting U-Boot when SPL support is active, it requires
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two downloads. imx_usb_loader downloads the SPL into
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OCRAM and starts it. SPL will check for a valid u-boot.img, and
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because it is not found, it will wait for it using the y-modem
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protocol via the console.
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A first install is then possible by combining imx_usb_loader with
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another tool such as kermit.
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sudo ../imx_usb_loader/imx_usb -v SPL
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kermit kermit_uboot
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and kermit_uboot contains something like this (set line should be adjusted):
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set line /dev/ttyUSB1
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set speed 115200
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SET CARRIER-WATCH OFF
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set flow-control none
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set handshake none
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set prefixing all
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set file type bin
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set protocol ymodem
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send u-boot.img
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c
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The last "c" command tells kermit (from ckermit package in most distros)
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to switch from command line mode to communication mode, and when the
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script is finished, the U-Boot prompt is shown in the same shell.
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