105 lines
3.5 KiB
ReStructuredText
105 lines
3.5 KiB
ReStructuredText
Freescale i.MX
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==============
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Freescale i.MX is traditionally very well supported under barebox.
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Depending on the SoC, there are different Boot Modes supported. Older
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SoCs up to i.MX31 support only the external Boot Mode. Newer SoCs
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can be configured for internal or external Boot Mode with the internal
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boot mode being the more popular mode. The i.MX23 and i.MX28, also
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known as i.MXs, are special. These SoCs have a completely different
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boot mechanism.
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Internal Boot Mode
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------------------
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The Internal Boot Mode is supported on:
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* i.MX25
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* i.MX35
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* i.MX51
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* i.MX53
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* i.MX6
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With the Internal Boot Mode, the images contain a header which describes
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where the binary shall be loaded and started. These headers also contain
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a so-called DCD table which consists of register/value pairs. These are
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executed by the Boot ROM and are used to configure the SDRAM. In barebox,
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the i.MX images are generated with the ``scripts/imx/imx-image`` tool.
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Normally it's not necessary to call this tool manually, it is executed
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automatically at the end of the build process.
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The images generated by the build process can be directly written to an
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SD card::
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# with Multi Image support:
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cat images/barebox-freescale-imx51-babbage.img > /dev/sdd
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# otherwise:
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cat barebox-flash-image > /dev/sdd
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The above will overwrite the MBR (and consequently the partition table)
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on the destination SD card. To preserve the MBR while writing the rest
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of the image to the card, use::
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dd if=images/barebox-freescale-imx51-babbage.img of=/dev/sdd bs=512 skip=1 seek=1
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The images can also always be started second stage::
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bootm /mnt/tftp/barebox-freescale-imx51-babbage.img
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USB Boot
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^^^^^^^^
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Most boards can be explicitly configured for USB Boot Mode or fall back
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to USB Boot when no other medium can be found. The barebox repository
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contains a USB upload tool. As it depends on the libusb development headers,
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it is not built by default. Enable it explicitly in ``make menuconfig``
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and install the libusb development package. On Debian, this can be done
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with ``apt-get install libusb-dev``. After compilation, the tool can be used
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with only the image name as argument::
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scripts/imx/imx-usb-loader images/barebox-freescale-imx51-babbage.img
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External Boot Mode
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------------------
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The External Boot Mode is supported by the older i.MX SoCs:
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* i.MX1
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* i.MX21
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* i.MX27
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* i.MX31
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(It may be supported on newer SoCs as well, but it is not widely used there.)
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The External Boot Mode supports booting only from NOR and NAND flash. On NOR
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flash, the binary is started directly on its physical address in memory. Booting
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from NAND flash is more complicated. The NAND flash controller copies the first
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2kb of the image to the NAND Controller's internal SRAM. This initial binary
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portion then has to:
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* Set up the SDRAM
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* Copy the initial binary to SDRAM to make the internal SRAM in the NAND flash
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controller free for use for the controller
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* Copy the whole barebox image to SDRAM
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* Start the image
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It is possible to write the image directly to NAND. However, since NAND flash
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can have bad blocks which must be skipped during writing the image and also
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by the initial loader, it is recommended to use the :ref:`command_barebox_update`
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command for writing to NAND flash.
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i.MX boards
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-----------
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Not supported all boards have a description here. Many newer boards also do
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not have individual defconfig files, they are covered by ``imx_v7_defconfig``
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or ``imx_defconfig`` instead.
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.. toctree::
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:glob:
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:numbered:
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:maxdepth: 1
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imx/*
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mxs/*
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