u-boot/doc/usage/index.rst
Sebastian Reichel 1db4c0ac77 usb: tcpm: add core framework
This adds TCPM framework in preparation for fusb302 support, which can
handle USB power delivery messages. This is needed to solve issues with
devices, that are running from a USB-C port supporting USB-PD, but not
having a battery.

Such a device currently boots to the kernel without interacting with
the power-supply at all. If there are no USB-PD message replies within
5 seconds, the power-supply assumes the peripheral is not capable of
USB-PD. It usually takes more than 5 seconds for the system to reach
the kernel and probe the I2C based fusb302 chip driver. Thus the
system always runs into this state. The power-supply's solution to
fix this error state is a hard reset, which involves removing the
power from VBUS. Boards without a battery (or huge capacitors) will
reset at this point resulting in a boot loop.

This imports the TCPM framework from the kernel. The porting has
originally been done by Rockchip using hardware timers and the Linux
kernel's TCPM code from some years ago.

I had a look at upgrading to the latest TCPM kernel code, but that
beast became a lot more complex due to adding more USB-C features.
I believe these features are not needed in U-Boot and with multiple
kthreads and hrtimers being involved it is non-trivial to port them.
Instead I worked on stripping down features from the Rockchip port
to an even more basic level. Also the TCPM code has been reworked
to avoid complete use of any timers (Rockchip used SoC specific
hardware timers + IRQ to implement delayed work mechanism). Instead
the delayed state changes are handled directly from the poll loop.

Note, that (in contrast to the original Rockchip port) the state
machine has the same hard reset quirk, that the kernel has - i.e.
it avoids disabling the CC pin resistors for devices that are not
self-powered. Without that quirk, the Radxa Rock 5B will not just
end up doing a machine reset when a hard reset is triggered, but will
not even recover, because the CPU will loose power and the FUSB302
will keep this state because of leak voltage arriving through the RX
serial pin (assuming a serial adapter is connected).

This also includes a 'tcpm' command, which can be used to get
information about the current state and the negotiated voltage
and current.

Co-developed-by: Wang Jie <dave.wang@rock-chips.com>
Signed-off-by: Wang Jie <dave.wang@rock-chips.com>
Tested-by: Soeren Moch <smoch@web.de>
Tested-by: Anand Moon <linux.amoon@gmail.com>
Reviewed-by: Jonas Karlman <jonas@kwiboo.se>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
2024-10-17 03:12:47 +02:00

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Use U-Boot
==========
.. toctree::
:maxdepth: 1
spl_boot
blkmap
dfu
environment
fdt_overlays
fit/index
netconsole
partitions
cmdline
semihosting
measured_boot
upl
Shell commands
--------------
.. toctree::
:maxdepth: 1
cmd/acpi
cmd/addrmap
cmd/armffa
cmd/askenv
cmd/base
cmd/bdinfo
cmd/bind
cmd/blkcache
cmd/bootd
cmd/bootdev
cmd/bootefi
cmd/bootelf
cmd/bootflow
cmd/booti
cmd/bootm
cmd/bootmenu
cmd/bootmeth
cmd/bootz
cmd/button
cmd/cat
cmd/cbsysinfo
cmd/cedit
cmd/cli
cmd/cls
cmd/cmp
cmd/coninfo
cmd/conitrace
cmd/cp
cmd/cpu
cmd/cyclic
cmd/dm
cmd/ebtupdate
cmd/echo
cmd/efi
cmd/eficonfig
cmd/env
cmd/event
cmd/exception
cmd/exit
cmd/extension
cmd/false
cmd/fatinfo
cmd/fatload
cmd/fdt
cmd/font
cmd/for
cmd/fwu_mdata
cmd/gpio
cmd/gpt
cmd/history
cmd/host
cmd/if
cmd/itest
cmd/imxtract
cmd/load
cmd/loadb
cmd/loadm
cmd/loads
cmd/loadx
cmd/loady
cmd/mbr
cmd/md
cmd/mmc
cmd/mtest
cmd/mtrr
cmd/panic
cmd/part
cmd/pause
cmd/pinmux
cmd/printenv
cmd/pstore
cmd/pwm
cmd/qfw
cmd/read
cmd/reset
cmd/rng
cmd/saves
cmd/sbi
cmd/scmi
cmd/scp03
cmd/seama
cmd/setexpr
cmd/sf
cmd/size
cmd/sleep
cmd/sm
cmd/smbios
cmd/sound
cmd/source
cmd/tcpm
cmd/temperature
cmd/tftpput
cmd/trace
cmd/true
cmd/upl
cmd/ums
cmd/unbind
cmd/ut
cmd/wdt
cmd/wget
cmd/write
cmd/xxd
Booting OS
----------
.. toctree::
:maxdepth: 1
os/plan9
os/vxworks