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Describe the current situation wrt the handling of USB devices on AM33xx based boards, taking the example of a common board (the Beagle Bone Black) and explaining how the different USB gadgets can be used. Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
265 lines
9.8 KiB
ReStructuredText
265 lines
9.8 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0+ OR BSD-3-Clause
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.. sectionauthor:: Tom Rini <trini@konsulko.com>
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AM335x Generation
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=================
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Summary
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-------
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This document covers various features of the `am335x_evm` default
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configuration, some of the related defconfigs, and how to enable hardware
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features not present by default in the defconfigs.
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Hardware
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--------
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The binary produced by this board supports, based on parsing of the EEPROM
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documented in TI's reference designs:
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* AM335x GP EVM
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* AM335x EVM SK
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* The Beaglebone family of designs
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Customization
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-------------
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Given that all of the above boards are reference platforms (and the
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Beaglebone platforms are OSHA), it is likely that this platform code and
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configuration will be used as the basis of a custom platform. It is
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worth noting that aside from things such as NAND or MMC only being
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required if a custom platform makes use of these blocks, the following
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are required, depending on design:
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* GPIO is only required if DDR3 power is controlled in a way similar to EVM SK
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* SPI is only required for SPI flash, or exposing the SPI bus.
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The following blocks are required:
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* I2C, to talk with the PMIC and ensure that we do not run afoul of
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errata 1.0.24.
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When removing options as part of customization, note that you will likely need
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to look at both `include/configs/am335x_evm.h`,
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`include/configs/ti_am335x_common.h` and `include/configs/am335x_evm.h` as the
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migration to Kconfig is not yet complete.
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NAND
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----
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The AM335x GP EVM ships with a 256MiB NAND available in most profiles. In
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this example to program the NAND we assume that an SD card has been
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inserted with the files to write in the first SD slot and that mtdparts
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have been configured correctly for the board. All images are first loaded
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into memory, then written to NAND.
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Step-1: Building u-boot for NAND boot
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Set following CONFIGxx options for NAND device.
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CONFIG_SYS_NAND_PAGE_SIZE number of main bytes in NAND page
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CONFIG_SYS_NAND_OOBSIZE number of OOB bytes in NAND page
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CONFIG_SYS_NAND_BLOCK_SIZE number of bytes in NAND erase-block
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CFG_SYS_NAND_ECCPOS ECC map for NAND page
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CONFIG_NAND_OMAP_ECCSCHEME (refer doc/README.nand)
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Step-2: Flashing NAND via MMC/SD
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.. code-block:: text
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# select BOOTSEL to MMC/SD boot and boot from MMC/SD card
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U-Boot # mmc rescan
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# erase flash
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U-Boot # nand erase.chip
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U-Boot # env default -f -a
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U-Boot # saveenv
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# flash MLO. Redundant copies of MLO are kept for failsafe
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U-Boot # load mmc 0 0x82000000 MLO
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U-Boot # nand write 0x82000000 0x00000 0x20000
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U-Boot # nand write 0x82000000 0x20000 0x20000
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U-Boot # nand write 0x82000000 0x40000 0x20000
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U-Boot # nand write 0x82000000 0x60000 0x20000
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# flash u-boot.img
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U-Boot # load mmc 0 0x82000000 u-boot.img
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U-Boot # nand write 0x82000000 0x80000 0x60000
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# flash kernel image
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U-Boot # load mmc 0 0x82000000 uImage
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U-Boot # nand write 0x82000000 ${nandsrcaddr} ${nandimgsize}
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# flash filesystem image
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U-Boot # load mmc 0 0x82000000 filesystem.img
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U-Boot # nand write 0x82000000 ${loadaddress} 0x300000
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Step-3: Set BOOTSEL pin to select NAND boot, and POR the device.
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The device should boot from images flashed on NAND device.
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Falcon Mode
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-----------
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The default build includes "Falcon Mode" (see doc/README.falcon) via NAND,
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eMMC (or raw SD cards) and FAT SD cards. Our default behavior currently is
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to read a 'c' on the console while in SPL at any point prior to loading the
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OS payload (so as soon as possible) to opt to booting full U-Boot. Also
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note that while one can program Falcon Mode "in place" great care needs to
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be taken by the user to not 'brick' their setup. As these are all eval
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boards with multiple boot methods, recovery should not be an issue in this
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worst-case however.
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Falcon Mode: eMMC
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-----------------
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The recommended layout in this case is:
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.. code-block:: text
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MMC BLOCKS |--------------------------------| LOCATION IN BYTES
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0x0000 - 0x007F : MBR or GPT table : 0x000000 - 0x020000
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0x0080 - 0x00FF : ARGS or FDT file : 0x010000 - 0x020000
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0x0100 - 0x01FF : SPL.backup1 (first copy used) : 0x020000 - 0x040000
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0x0200 - 0x02FF : SPL.backup2 (second copy used) : 0x040000 - 0x060000
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0x0300 - 0x06FF : U-Boot : 0x060000 - 0x0e0000
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0x0700 - 0x08FF : U-Boot Env + Redundant : 0x0e0000 - 0x120000
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0x0900 - 0x28FF : Kernel : 0x120000 - 0x520000
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Note that when we run 'spl export' it will prepare to boot the kernel.
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This includes relocation of the uImage from where we loaded it to the entry
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point defined in the header. As these locations overlap by default, it
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would leave us with an image that if written to MMC will not boot, so
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instead of using the loadaddr variable we use 0x81000000 in the following
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example. In this example we are loading from the network, for simplicity,
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and assume a valid partition table already exists and 'mmc dev' has already
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been run to select the correct device. Also note that if you previously
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had a FAT partition (such as on a Beaglebone Black) it is not enough to
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write garbage into the area, you must delete it from the partition table
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first.
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.. code-block:: text
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# Ensure we are able to talk with this mmc device
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U-Boot # mmc rescan
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U-Boot # tftp 81000000 am335x/MLO
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# Write to two of the backup locations ROM uses
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U-Boot # mmc write 81000000 100 100
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U-Boot # mmc write 81000000 200 100
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# Write U-Boot to the location set in the config
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U-Boot # tftp 81000000 am335x/u-boot.img
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U-Boot # mmc write 81000000 300 400
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# Load kernel and device tree into memory, perform export
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U-Boot # tftp 81000000 am335x/uImage
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U-Boot # run findfdt
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U-Boot # tftp ${fdtaddr} am335x/${fdtfile}
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U-Boot # run mmcargs
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U-Boot # spl export fdt 81000000 - ${fdtaddr}
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# Write the updated device tree to MMC
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U-Boot # mmc write ${fdtaddr} 80 80
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# Write the uImage to MMC
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U-Boot # mmc write 81000000 900 2000
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Falcon Mode: FAT SD cards
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-------------------------
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In this case the additional file is written to the filesystem. In this
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example we assume that the uImage and device tree to be used are already on
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the FAT filesystem (only the uImage MUST be for this to function
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afterwards) along with a Falcon Mode aware MLO and the FAT partition has
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already been created and marked bootable:
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.. code-block:: text
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U-Boot # mmc rescan
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# Load kernel and device tree into memory, perform export
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U-Boot # load mmc 0:1 ${loadaddr} uImage
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U-Boot # run findfdt
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U-Boot # load mmc 0:1 ${fdtaddr} ${fdtfile}
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U-Boot # run mmcargs
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U-Boot # spl export fdt ${loadaddr} - ${fdtaddr}
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This will print a number of lines and then end with something like:
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.. code-block:: text
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Using Device Tree in place at 80f80000, end 80f85928
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Using Device Tree in place at 80f80000, end 80f88928
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So then you:
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.. code-block:: text
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U-Boot # fatwrite mmc 0:1 0x80f80000 args 8928
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Falcon Mode: NAND
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-----------------
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In this case the additional data is written to another partition of the
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NAND. In this example we assume that the uImage and device tree to be are
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already located on the NAND somewhere (such as filesystem or mtd partition)
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along with a Falcon Mode aware MLO written to the correct locations for
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booting and mtdparts have been configured correctly for the board:
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.. code-block:: text
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U-Boot # nand read ${loadaddr} kernel
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U-Boot # load nand rootfs ${fdtaddr} /boot/am335x-evm.dtb
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U-Boot # run nandargs
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U-Boot # spl export fdt ${loadaddr} - ${fdtaddr}
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U-Boot # nand erase.part u-boot-spl-os
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U-Boot # nand write ${fdtaddr} u-boot-spl-os
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USB device
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----------
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The platform code for am33xx based designs is legacy in the sense that
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it is not fully compliant with the driver model in its management of the
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various resources. This is particularly true for the USB Ethernet gadget
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which will automatically be bound to the first USB Device Controller
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(UDC). This make the USB Ethernet gadget work out of the box on common
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boards like the Beagle Bone Blacks and by default will prevents other
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gadgets to be used.
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The output of the 'dm tree' command shows which driver is bound to which
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device, so the user can easily configure their platform differently from
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the command line:
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.. code-block:: text
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=> dm tree
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Class Index Probed Driver Name
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-----------------------------------------------------------
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[...]
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misc 0 [ + ] ti-musb-wrapper | |-- usb@47400000
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usb 0 [ + ] ti-musb-peripheral | | |-- usb@47401000
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ethernet 1 [ + ] usb_ether | | | `-- usb_ether
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bootdev 3 [ ] eth_bootdev | | | `-- usb_ether.bootdev
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usb 0 [ ] ti-musb-host | | `-- usb@47401800
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Typically here any network command performed using the usb_ether
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interface would work, while using other gadgets would fail:
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.. code-block:: text
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=> fastboot usb 0
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All UDC in use (1 available), use the unbind command
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g_dnl_register: failed!, error: -19
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exit not allowed from main input shell.
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As hinted by the primary error message, the only controller available
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(usb@47401000) is currently bound to the usb_ether driver, which makes
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it impossible for the fastboot command to bind with this device (at
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least from a bootloader point of view). The solution here would be to
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use the unbind command specifying the class and index parameters (as
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shown above in the 'dm tree' output) to target the driver to unbind:
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.. code-block:: text
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=> unbind ethernet 1
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The output of the 'dm tree' command now shows the availability of the
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first USB device controller, the fastboot gadget will now be able to
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bind with it:
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.. code-block:: text
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=> dm tree
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Class Index Probed Driver Name
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-----------------------------------------------------------
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[...]
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misc 0 [ + ] ti-musb-wrapper | |-- usb@47400000
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usb 0 [ ] ti-musb-peripheral | | |-- usb@47401000
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usb 0 [ ] ti-musb-host | | `-- usb@47401800
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