Commit graph

69027 commits

Author SHA1 Message Date
Sean Anderson
66e7348fe7 firmware: scmi: Include device_compat.h
This header is necessary for the dev_xxx macros.

Signed-off-by: Sean Anderson <seanga2@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
2020-10-15 18:36:55 -04:00
Sean Anderson
4d55155f6c dm: syscon: Set LOG_CATEGORY
We call log_debug, but do not have a category set.

Signed-off-by: Sean Anderson <seanga2@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
2020-10-15 18:36:55 -04:00
Sean Anderson
0f0f4e5feb clk: sifive: Include device_compat.h
Necessary for dev_xxx.

Signed-off-by: Sean Anderson <seanga2@gmail.com>
2020-10-15 18:36:55 -04:00
Tom Rini
9dc6aef8c9 Merge tag 'mmc-2020-10-14' of https://gitlab.denx.de/u-boot/custodians/u-boot-mmc
- fsl_esdhc_imx cleanup
- not send cm13 if send_status is 0.
- Add reinit API
- Add mmc HS400 for fsl_esdhc
- Several cleanup for fsl_esdhc
- Add ADMA2 for sdhci
2020-10-15 08:20:42 -04:00
Andre Heider
c87afd39d1 configs: smdkv310: get rid of unused EXYNOS4_DEFAULT_UART_OFFSET
Unused.

Signed-off-by: Andre Heider <a.heider@gmail.com>
Acked-by: Krzysztof Kozlowski <krzk@kernel.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>
2020-10-15 13:33:22 +09:00
Andre Heider
023951038f Remove whitelist entry CONFIG_DEFAULT_CONSOLE
There're no users left.

Signed-off-by: Andre Heider <a.heider@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>
2020-10-15 13:33:22 +09:00
Andre Heider
9c04265f76 treewide: configs: fold CONFIG_DEFAULT_CONSOLE
In prepartion to remove CONFIG_DEFAULT_CONSOLE, fold the current users.

Signed-off-by: Andre Heider <a.heider@gmail.com>
Acked-by: Krzysztof Kozlowski <krzk@kernel.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>
2020-10-15 13:33:22 +09:00
Andre Heider
ac79cfc2a4 treewide: configs: get rid of unused CONFIG_DEFAULT_CONSOLE
These are all unused.

Signed-off-by: Andre Heider <a.heider@gmail.com>
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Acked-by: Krzysztof Kozlowski <krzk@kernel.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>
2020-10-15 13:33:22 +09:00
Tom Rini
0f35d96bfd Merge https://gitlab.denx.de/u-boot/custodians/u-boot-marvell
- Octeon TX: Add NAND driver (Suneel)
- Octeon TX: Add NIC driver driver (Suneel)
- Octeon TX2: Add NIC driver driver (Suneel)
- Armada 8040: Add iEi Puzzle-M80 board support (Luka)
- Armada A37xx SPI: Add support for CS-GPIO (George)
- Espressobin: Use Linux model/compatible strings (Andre)
- Espressobin: Add armada-3720-espressobin-emmc.dts from Linux (Andre)
- Armada A37xx: Small cleanup of config header (Pali)
2020-10-14 13:51:56 -04:00
Tom Rini
6731c5a5ef Merge branch '2020-10-14-assorted-changes'
- Add support for Linux "pstore" dumps.
- Button command fixup.
- gd cleanup and documentation.
- Assorted other cleanups.
2020-10-14 13:35:05 -04:00
Heinrich Schuchardt
40a3008632 doc: Sphinx.override_domain() deprecated
Sphinx.override_domain() is deprecated since Sphinx 1.8 and removed in
Sphinx 3.

Use Sphinx.add_domain(, override=True) instead.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
2020-10-14 11:16:34 -04:00
Christian Gmeiner
c90778ad70 net: e1000: add defaults for i210 TX/RX PBSIZE
Set the defaults on probe for the packet buffer size registers
for the i210.

The TX/RX PBSIZE register of the i210 resets to its default value
only at power-on - see Intel Ethernet Controller I210 Datasheet rev 3.5
chapter 8.3 'Internal Packet Buffer Size Registers'.

If something (another driver, another OS, etc.) modifies this register
from its default value, the e1000 driver doesn't function correctly. It
detects a hang of the transmitter and continuously resets the adapter.
Here we set this value to its default when resetting the i210 to
resolve this issue.

Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>
2020-10-14 11:16:34 -04:00
Alper Nebi Yasak
b9cca2c57a checkpatch.pl: Make CONFIG_IS_ENABLED(CONFIG_*) an error
CONFIG_IS_ENABLED() takes the kconfig name without the CONFIG_ prefix,
e.g. CONFIG_IS_ENABLED(CLK) for CONFIG_CLK. Make including the prefix
an error in checkpatch.pl so calls in the wrong format aren't
accidentally reintroduced.

Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
2020-10-14 11:16:34 -04:00
Alper Nebi Yasak
957a3e5493 treewide: Fix wrong CONFIG_IS_ENABLED() handling
CONFIG_IS_ENABLED() takes the kconfig name without the CONFIG_ prefix,
e.g. CONFIG_IS_ENABLED(CLK) for CONFIG_CLK. Some of these were being
fixed every now and then, see:

    commit 71ba2cb0d6 ("board: stm32mp1: correct CONFIG_IS_ENABLED usage for LED")
    commit a5ada25e42 ("rockchip: clk: fix wrong CONFIG_IS_ENABLED handling")
    commit 5daf6e56d3 ("common: console: Fix duplicated CONFIG in silent env callback")
    commit 48bfc31b64 ("MIPS: bootm: Fix broken boot_env_legacy codepath")

Fix all files found by `git grep "CONFIG_IS_ENABLED(CONFIG"` by running
':%s/CONFIG_IS_ENABLED(CONFIG_\(\w+\))/CONFIG_IS_ENABLED(\1)/g' in vim.

Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
2020-10-14 11:16:34 -04:00
Heinrich Schuchardt
467d90a37e doc: global data pointer
Add the description of the global data pointer to the generated HTML
documentation.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
2020-10-14 11:16:34 -04:00
Heinrich Schuchardt
0c7cd15f3f global_data.h: add Sphinx documentation
Add the missing Sphinx documentation for struct global_data and
gd_board_type().

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
2020-10-14 11:16:34 -04:00
Heinrich Schuchardt
c82a97bc5c global_data.h: convert GD_FLG_* to enum
Sphinx documentation is only available for enums not for #defines.
Anyway it is better to keep related definitions in an enum.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
2020-10-14 11:16:34 -04:00
Heinrich Schuchardt
73fdb9558e bootm: add {arch,board}_preboot_os() to bootm.h
Functions that are used in multiple C modules should be defined in an
include.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Michael Walle <michael@walle.cc>
2020-10-14 11:16:34 -04:00
Sean Anderson
4b2be78ab6 time: Fix get_ticks being non-monotonic
get_ticks does not always succeed. Sometimes it can be called before the
timer has been initialized. If it does, it returns a negative errno.
This causes the timer to appear non-monotonic, because the value will
become much smaller after the timer is initialized.

No users of get_ticks which I checked handle errors of this kind. Further,
functions like tick_to_time mangle the result of get_ticks, making it very
unlikely that one could check for an error without suggesting a patch such
as this one.

This patch panics if we ever get an error. There are two cases in which
this can occur. The first is if we couldn't find/probe the timer for some
reason. One reason for this is if the timer is not available so early. This
likely indicates misconfiguration. Another reason is that the timer has an
invalid/missing device tree binding. In this case, panicing is also
correct. The second case covers errors calling get_count. This can only
occur if the timer is missing a get_count function (or on RISC-V, but that
should be fixed soon).

Fixes: c8a7ba9e6a
Signed-off-by: Sean Anderson <seanga2@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
2020-10-14 11:16:34 -04:00
Otavio Salvador
d74fcee2d8 spl: Add SPL_SERIAL as requirement for SDP_USB_SDP
The USB SDP protocol require the SPL serial support to allow the build
to succeed.

Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>
2020-10-14 11:16:34 -04:00
Otavio Salvador
f9b9b77933 spl: Avoid printing boot device if silent console is enabled
Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Stefan Roese <sr@denx.de>
2020-10-14 11:16:34 -04:00
David Woodhouse
b0493bb75a env/ext4.c: allow loading from an EXT4 partition on the MMC boot device
This parallels what I added for FAT in commit 6731bef696, allowing the
environment to be found in a specific partition on the device that the
board's mmc_get_env_dev() returns. On the Banana Pi R2 that means the
device that U-Boot was loaded from; either the internal eMMC or an SD
card.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>
2020-10-14 11:16:34 -04:00
David Woodhouse
4dee3f7851 mmc: remove duplicate mmc_get_env_dev() implementations
Since it's so trivial I could just about tolerate this when there were only
two copies of it. But now there are about to be three.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>
2020-10-14 11:16:34 -04:00
Heinrich Schuchardt
684710dc33 arm: enable DM_RNG on QEMU by default
The EFI_RNG_PROTOCOL is needed for address randomization in Linux.
We should provide it by default on QEMU.

Reported-by: François Ozog <francois.ozog@linaro.org>
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
2020-10-14 11:16:34 -04:00
Heinrich Schuchardt
a6bfd71a96 cmd/button: return button status
To make the button command useful in a shell script it should return the
status of the button:

* 0 (true) - pressed, on
* 1 (false) - not pressed, off

The button command takes only one argument. Correct maxargs.

Adjust the Python unit test.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Philippe Reynes <philippe.reynes@softathome.com>
2020-10-14 11:16:34 -04:00
Heinrich Schuchardt
7cd96a4728 drivers: gpio: keep output value for input on sandbox
For testing purposes keep the output value when switching to input.
This allows us to manipulate the input value via the gpio command.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Philippe Reynes <philippe.reynes@softathome.com>
2020-10-14 11:16:34 -04:00
Heinrich Schuchardt
39916bb45f test: sharpen button label unit test
Using different strings for the device tree node labels and the label
property of buttons sharpens the button label unit test.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Philippe Reynes <philippe.reynes@softathome.com>
2020-10-14 11:16:34 -04:00
Frédéric Danis
9ea0a1ee93 cmd: Fixup DT to pass PStore Ramoops parameters
To simplify configuration and keep synchronized the PStore/Ramoops between
U-Boot and the Linux kernel, this commit dynamically adds the Ramoops
parameters defined in the U-Boot session to the Device Tree.

Signed-off-by: Frédéric Danis <frederic.danis@collabora.com>
Cc: Tom Rini <trini@konsulko.com>
Cc: Heinrich Schuchardt <xypron.glpk@gmx.de>
Cc: Wolfgang Denk <wd@denx.de>
Cc: Heiko Schocher <hs@denx.de>
2020-10-14 11:16:34 -04:00
Frédéric Danis
26f555a6e5 test: Add PStore command tests
Add PStore command to sandbox and sandbox64 defconfigs.
Add test checking:
- 'pstore display' of all records
- 'pstore display' only the 2nd dump record
- 'pstore save' of all records

Signed-off-by: Frédéric Danis <frederic.danis@collabora.com>
[trini: Adjust to always load files from source directory]
Signed-off-by: Tom Rini <trini@konsulko.com>
Cc: Heinrich Schuchardt <xypron.glpk@gmx.de>
Cc: Wolfgang Denk <wd@denx.de>
Cc: Heiko Schocher <hs@denx.de>
2020-10-14 11:16:34 -04:00
Frédéric Danis
9744d1a547 cmd: Add command to display or save Linux PStore dumps
This patch adds a new pstore command allowing to display or save ramoops
logs (oops, panic, console, ftrace and user) generated by a previous
kernel crash.
PStore parameters can be set in U-Boot configuration file, or at run-time
using "pstore set" command. Records size should be the same as the ones
used by kernel, and should be a power of 2.
This command allows:
- to display uncompressed logs
- to save compressed or uncompressed logs, compressed logs are saved as a
  compressed stream, it may need some work to be able to decompress it,
  e.g. adding a fake header:
  "printf "\x1f\x8b\x08\x00\x00\x00\x00\x00\x00\x00" |
  cat - dmesg-ramoops-0.enc.z | gzip -dc"
- ECC part is not used to check memory corruption
- only 1st FTrace log is displayed or saved

Signed-off-by: Frédéric Danis <frederic.danis@collabora.com>
[trini: Minor updates for current design, correct spacing in rST]
Signed-off-by: Tom Rini <trini@konsulko.com>
Cc: Heinrich Schuchardt <xypron.glpk@gmx.de>
Cc: Wolfgang Denk <wd@denx.de>
Cc: Heiko Schocher <hs@denx.de>
2020-10-14 11:16:19 -04:00
Michael Walle
361a422b90 mmc: fsl_esdhc: add ADMA2 support
Newer eSDHC controllers support ADMA2 descriptor tables which support
64bit DMA addresses. One notable user of addresses in the upper memory
segment is the EFI loader.

If support is enabled, but the controller doesn't support ADMA2, we
will fall back to SDMA (and thus 32 bit DMA addresses only).

Signed-off-by: Michael Walle <michael@walle.cc>
2020-10-14 14:00:44 +08:00
Michael Walle
52faec3182 mmc: fsl_esdhc: replace most #ifdefs by IS_ENABLED()
Make the code cleaner and drop the old-style #ifdef constructs where it is
possible.

Signed-off-by: Michael Walle <michael@walle.cc>
2020-10-14 14:00:37 +08:00
Pali Rohár
8369886b40 arm: mvebu: Remove old comments from configs/mvebu_armada-37xx.h file
These comments are relict for old, now removed config options.
So remove these obsoleted comments too.

Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Stefan Roese <sr@denx.de>
2020-10-14 07:56:17 +02:00
Andre Heider
f1a43c84a9 arm64: dts: a3720: add support for espressobin with populated emmc
Import armada-3720-espressobin-emmc.dts from Linux, but use sdhc1 for
emmc, since our dtsi is still based on downstream and sdhc0 is used for
the sd card.

Signed-off-by: Andre Heider <a.heider@gmail.com>
2020-10-14 07:56:17 +02:00
Andre Heider
03bb6a9b1e arm64: dts: armada-3720-espressobin: split common parts to .dtsi
Move most of the dts to the new common armada-3720-espressobin.dtsi
file, just like Linux, but keep the current, downstream based, version.

The dts itself is imported from Linux.

Signed-off-by: Andre Heider <a.heider@gmail.com>
2020-10-14 07:56:17 +02:00
Andre Heider
559ae35c96 arm64: dts: armada-3720-espressobin: use Linux model/compatible strings
Fix the actual board vendor and ease synching dts files from Linux.

Signed-off-by: Andre Heider <a.heider@gmail.com>
Reviewed-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Stefan Roese <sr@denx.de>
2020-10-14 07:55:56 +02:00
George Hilliard
2df286390a spi: mvebu_a3700_spi: add support for cs-gpios
The device tree has a way to specify GPIO lines as chip selects.  From
the binding docs:

    So if for example the controller has 2 CS lines, and the cs-gpios
    property looks like this:

    cs-gpios = <&gpio1 0 0> <0> <&gpio1 1 0> <&gpio1 2 0>;

    Then it should be configured so that num_chipselect = 4 with the
    following mapping:

    cs0 : &gpio1 0 0
    cs1 : native
    cs2 : &gpio1 1 0
    cs3 : &gpio1 2 0

Add support for this, while retaining backward-compatibility with
existing device trees; the driver will preserve existing behavior if a
cs-gpios list is not given, or if a particular line is specified as <0>
(native).

This implementation is inspired by similar implementations in
neighboring drivers for other platforms: atmega, mxc, etc.

Signed-off-by: George Hilliard <ghilliar@amazon.com>
Reviewed-by: Stefan Roese <sr@denx.de>
2020-10-14 07:55:56 +02:00
Luka Kovacic
87c220d041 arm: mvebu: mvebu_armada-8k: Add support for initializing iEi Puzzle-M801 networking
Add support for the marvell,armada8040-puzzle-m801 compatible string
in the board/Marvell/mvebu_armada-8k/board.c file to initialize the
networking on iEi Puzzle-M801 board (2x CP1 1 Gb ports).

Signed-off-by: Luka Kovacic <luka.kovacic@sartura.hr>
Cc: Luka Perkov <luka.perkov@sartura.hr>
Reviewed-by: Stefan Roese <sr@denx.de>
2020-10-14 07:55:56 +02:00
Luka Kovacic
2ae2b8a2f2 arm: mvebu: Initial iEi Puzzle-M801 support
Add initial U-Boot support for the iEi Puzzle-M801 board based on the
Marvell Armada 88F8040 SoC.

Currently supported hardware:
1x USB 3.0
4x Gigabit Ethernet
2x SFP+ (with NXP PCA9555 and NXP PCA9544)
1x SATA 3.0
1x M.2 type B
1x RJ45 UART
1x SPI flash
1x EPSON RX8010 RTC

Signed-off-by: Luka Kovacic <luka.kovacic@sartura.hr>
Cc: Luka Perkov <luka.perkov@sartura.hr>
Reviewed-by: Stefan Roese <sr@denx.de>
2020-10-14 07:55:56 +02:00
Suneel Garapati
4684a7a43a net: Add NIC controller driver for OcteonTX2
Adds support for Network Interface controllers found on
OcteonTX2 SoC platforms.

Signed-off-by: Suneel Garapati <sgarapati@marvell.com>
Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Joe Hershberger <joe.hershberger@ni.com>
2020-10-14 07:55:56 +02:00
Suneel Garapati
0008e9a69d net: Add NIC controller driver for OcteonTX
Adds support for Network Interface controllers found on
OcteonTX SoC platforms.

Signed-off-by: Suneel Garapati <sgarapati@marvell.com>
Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Joe Hershberger <joe.hershberger@ni.com>
2020-10-14 07:55:56 +02:00
Suneel Garapati
05c7606ac9 mtd: nand: Add NAND controller driver for OcteonTX
Adds support for NAND controllers found on OcteonTX or
OcteonTX2 SoC platforms. Also includes driver to support
Hardware ECC using BCH HW engine found on these platforms.

Signed-off-by: Aaron Williams <awilliams@marvell.com>
Signed-off-by: Suneel Garapati <sgarapati@marvell.com>
Signed-off-by: Stefan Roese <sr@denx.de>
2020-10-14 07:55:56 +02:00
Tom Rini
55fca74a5b Merge branch '2020-10-12-assorted-encryption-changes'
- Fix verified boot on BE targets
- Add support for multiple required keys in verified boots
- Add support for Initialization Vectors in AES keys in FIT images
- Assorted fixes in the RSA code
2020-10-13 10:04:17 -04:00
Heinrich Schuchardt
ec71cc34c1 lib: rsa: superfluous initialization in rsa_verify()
Remove initialization of ret with unused value.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
2020-10-12 21:30:38 -04:00
Rasmus Villemoes
3f8808ebaa rsa: fix retrieving public exponent on big-endian systems
Commit fdf0819afb (rsa: fix alignment issue when getting public
exponent) changed the logic to avoid doing an 8-byte access to a
possibly-not-8-byte-aligned address.

However, using rsa_convert_big_endian is wrong: That function converts
an array of big-endian (32-bit) words with the most significant word
first (aka a BE byte array) to an array of cpu-endian words with the
least significant word first. While the exponent is indeed _stored_ as
a big-endian 64-bit word (two BE words with MSW first), we want to
extract it as a cpu-endian 64 bit word. On a little-endian host,
swapping the words and byte-swapping each 32-bit word works, because
that's the same as byte-swapping the whole 64 bit word. But on a
big-endian host, the fdt32_to_cpu are no-ops, but
rsa_convert_big_endian() still does the word-swapping, breaking
verified boot.

To fix that, while still ensuring we don't do unaligned accesses, add
a little helper that first memcpy's the bytes to a local fdt64_t, then
applies fdt64_to_cpu(). [The name is chosen based on the
[bl]eXX_to_cpup in linux/byteorder/generic.h].

Fixes: fdf0819afb ("rsa: fix alignment issue when getting public exponent")
Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
Reviewed-by: Simon Glass <sjg@chromium.org>
2020-10-12 21:30:38 -04:00
Matthieu CASTET
167fb1f8dc lib: rsa: check algo match in rsa_verify_with_keynode
The algo name should match between the FIT's signature node and the
U-Boot's control FDT.

If we do not check it, U-Boot's control FDT can expect sha512 hash but
nothing will prevent to accept image with sha1 hash if the signature is correct.

Signed-off-by: Matthieu CASTET <castet.matthieu@free.fr>
2020-10-12 21:30:38 -04:00
Philippe Reynes
54ab7cf1dd fit: cipher: aes: allow to read the IV in the FIT image
This commit add the support in u-boot to read the IV
in the FIT image instead of u-boot device tree.

Signed-off-by: Philippe Reynes <philippe.reynes@softathome.com>
2020-10-12 21:30:38 -04:00
Philippe Reynes
a6982a6f76 fit: cipher: aes: allow to store the IV in the FIT image
Binaries may be encrypted in a FIT image with AES. This
algo needs a key and an IV (Initialization Vector). The
IV is provided in a file (pointer by iv-name-hint in the
ITS file) when building the ITB file.

This commits adds provide an alternative way to manage
the IV. If the property iv-name-hint is not provided in
the ITS file, the tool mkimage will generate an random
IV and store it in the FIT image.

Signed-off-by: Philippe Reynes <philippe.reynes@softathome.com>
2020-10-12 21:30:37 -04:00
Heinrich Schuchardt
34ca77c1e1 lib/hashtable: remove superfluous check
We assign first_deleted = 0. There is no need to check its value without
any further assignment in between.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
2020-10-12 21:30:37 -04:00
Thirupathaiah Annapureddy
6a0498a5fd doc: verified-boot: add required-mode information
Add documentation about 'required-mode' property in /signature node
in U-Boot's control FDT.

Signed-off-by: Thirupathaiah Annapureddy <thiruan@linux.microsoft.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
2020-10-12 21:30:37 -04:00