Nishanth Menon [Tue, 12 Jun 2018 20:24:08 +0000 (15:24 -0500)]
ARM: Introduce ability to enable ACR::IBE on Cortex-A8 for CVE-2017-5715
As recommended by Arm in [1], IBE[2] has to be enabled unconditionally
for BPIALL to be functional on Cortex-A8 processors. Provide a config
option for platforms to enable this option based on impact analysis
for products.
NOTE: This patch in itself is NOT the final solution, this requires:
a) Implementation of v7_arch_cp15_set_acr on SoCs which may not
provide direct access to ACR register.
b) Operating Systems such as Linux to provide adequate workaround in the right
locations.
c) This workaround applies to only the boot processor. It is important
to apply workaround as necessary (context-save-restore) around low
power context loss OR additional processors as necessary in either
firmware support OR elsewhere in OS.
Andrew Thomas [Mon, 18 Jun 2018 18:56:06 +0000 (11:56 -0700)]
dwc2 USB controller hangs with lan78xx
This bug is the combination of dwc2 USB controller and lan78xx
USB ethernet controller, which is the combination in use on
the Raspberry Pi Model 3 B+.
When the host attempts to receive a packet, but a packet has not
arrived, the lan78xx controller responds by setting BIR
(Bulk-In Empty Response) to NAK. Unfortunately, this hangs
the USB controller and requires the USB controller to
be reset.
The fix proposed is to have the lan78xx controller respond
by setting BIR to ZLP.
Signed-off-by: Andrew Thomas <andrew.thomas@oracle.com> Tested-by: Peter Robinson <pbrobinson@gmail.com> Reviewed-by: Alexander Graf <agraf@suse.de>
Joe Hershberger [Tue, 26 Jun 2018 09:37:59 +0000 (12:37 +0300)]
fw_printenv: Don't bail out directly after one env read error
When using a redundant environment a read error should simply mean to
not use that copy instead of giving up completely. The other copy may
be just fine.
Signed-off-by: Joe Hershberger <joe.hershberger@ni.com> Signed-off-by: Ioan-Adrian Ratiu <adrian.ratiu@ni.com>
Jörg Krause [Sun, 14 Jan 2018 18:26:40 +0000 (19:26 +0100)]
mtd: nand: mxs_nand_spl: add mxs_flash_full_ident
For now, the existing SPL MXS NAND driver only supports to identify
ONFi-compliant NAND chips. In order to allow identifying
non-ONFi-compliant chips add `mxs_flash_full_ident()` which uses the
`nand_get_flash_type()` functionality from `nand_base.c` to lookup
for supported NAND chips in the chip ID list.
For compatibility reason the full identification support is only
available if the config option `CONFIG_SPL_NAND_IDENT` is enabled.
The lookup was tested on a custom i.MX6ULL board with a Toshiba
TC58NVG1S3HTAI0 NAND chip.
Jörg Krause [Sun, 14 Jan 2018 18:26:39 +0000 (19:26 +0100)]
mtd: nand: mxs_nand_spl: refactor mxs_flash_ident
The existing `mxs_flash_ident()` is limited to identify ONFi compliant
NAND chips only. In order to support non-ONFi NAND chips refactor the
function and rename it to `mxs_flash_onfi_ident()`.
A follow-up patch will add `mxs_flash_full_ident()` which allows to use
the chip ID list to lookup for supported NAND flashs.
Jörg Krause [Sun, 14 Jan 2018 18:26:37 +0000 (19:26 +0100)]
mtd: nand: export nand_get_flash_type function
`nand_get_flash_type()` allows identification of supported NAND flashs.
The function is useful in SPL (like mxs_nand_spl.c) to lookup for a NAND
flash (which does not support ONFi) instead of using nand_simple.c and
hard-coding all required NAND parameters.
Since commit 1da1938d57b3 ("spl: Add default values for ARCH_MX7")
CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_USE_SECTOR is selected by default on
i.MX7 platforms, so remove it from the board defconfig.
Jagan Teki [Mon, 18 Jun 2018 05:42:19 +0000 (11:12 +0530)]
imx6ul: geam: Fix fdt_file mismatch
fdt_file is looking for imx6ul-geam-kit.dtb but Linux
has imx6ul-geam.dtb, since Linux skipped -kit on file name
by below commit.
"ARM: dts: imx6ul-geam: Skip suffix -kit from dts name"
(sha1: 182de5ebce71e469cfa686fcdf08c9cbe11ece97)
So, due to this mismatch U-Boot failed to pick the
proper dtb which eventually break the Linux boot.
This patch fixed this mismatch by
- renaming dts files
- update config option to use new dtb file
- update fdt_file to new dtb file name
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com> Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>
The PFUZE3000 uses registers addresses up to 0xff.
The DM pfuze100 driver supports both pfuze100 and pfuze3000. Allow it
to use the device type to return the correct number of registers.
Also rename the too generic PMIC_NUM_OF_REGS enumeration value for
pfuze3000 to match the other "PFUZE3000_" prefixed enumerations and the
pfuze100 enumeration value PFUZE100_NUM_OF_REGS.
Stefan Agner [Fri, 22 Jun 2018 16:06:18 +0000 (18:06 +0200)]
mtd: nand: mxs_nand: add support for specific ECC strength
Add support for specified ECC strength/size using device tree
properties nand-ecc-strength/nand-ecc-step-size.
This aligns behavior with the mainline driver, such that:
- If fsl,use-minimal-ecc is requested it will use data from
data sheet/ONFI. If this is not available the driver will fail.
- If nand-ecc-strength/nand-ecc-step-size are specified those
value will be used.
- By default maximum possible ECC strength is used
Signed-off-by: Stefan Agner <stefan.agner@toradex.com>
Stefan Agner [Fri, 22 Jun 2018 15:19:51 +0000 (17:19 +0200)]
mtd: nand: mxs_nand: add minimal ECC support
Add support for minimum ECC strength supported by the NAND chip.
This aligns with the behavior when using the fsl,use-minimum-ecc
device tree property in Linux.
Signed-off-by: Stefan Agner <stefan.agner@toradex.com>
Report correct ECC parameters back to the stack. Do not report
bytes as we have it not immeaditly available and the Linux version
also does not report it. It seems to have no aversive effect.
Signed-off-by: Stefan Agner <stefan.agner@toradex.com>
Stefan Agner [Fri, 22 Jun 2018 15:19:49 +0000 (17:19 +0200)]
mtd: nand: mxs_nand: use structure for BCH geometry
Calculate BCH geometry at start and store the information in
a structure. This avoids recalculation on every page access
and allows to calculate ECC relevant information in one place.
This patch does not change ECC layout or driver behavior in
any way.
The patch aligns the driver somewhat with the Linux GPMI NAND
driver which drives the same IP.
Signed-off-by: Stefan Agner <stefan.agner@toradex.com>
Stefan Agner [Fri, 22 Jun 2018 15:19:48 +0000 (17:19 +0200)]
mtd: nand: mxs_nand: allow to enable BBT support
Add config option which allows to enable on flash bad block table
support. This has the same effect as when using the device tree
property "nand-on-flash-bbt" in Linux.
Signed-off-by: Stefan Agner <stefan.agner@toradex.com>
Stefan Agner [Fri, 22 Jun 2018 15:19:46 +0000 (17:19 +0200)]
mtd: nand: mxs_nand: introduce SPL specific init
In preparation to convert the driver to use NAND self init
provide a new minimal init for SPL builds. As a side effect
this also reduces size of SPL by about 4KiB.
Signed-off-by: Stefan Agner <stefan.agner@toradex.com>
- ignored the responsible arguments (speed, mode)
The set speed/mode function must use the supplied function arguments to
work properly. With this commit we take those arguments and transfer
them to the priv-data.
- used wrong udevice pointer for getting priv data
the udevice-pointer within function argument is already the spi-bus
device, so it is wrong looking here for some parent (ocp-bus in this
case) and getting priv-pointer from there.
Signed-off-by: Hannes Schmelzer <oe5hpm@oevsv.at> Reviewed-by: Jagan Teki <jagan@openedev.com>
Bin Meng [Fri, 22 Jun 2018 08:38:30 +0000 (01:38 -0700)]
x86: efi: payload: Count in conventional memory above 4GB in DRAM bank
At present in dram_init_banksize() it ignores conventional memory
above 4GB. This leads to wrong DRAM size is printed during boot.
Remove such limitation.
Signed-off-by: Bin Meng <bmeng.cn@gmail.com> Reviewed-by: Simon Glass <sjg@chromium.org>
Bin Meng [Fri, 22 Jun 2018 08:38:27 +0000 (01:38 -0700)]
x86: Change __kernel_size_t conditionals to use compiler provided defines
Since commit bb0bb91cf0aa ("efi_stub: Use efi_uintn_t"), EFI x86
64-bit payload does not work anymore. The call to GetMemoryMap()
in efi_stub.c fails with return code EFI_INVALID_PARAMETER. Since
the payload itself is still 32-bit U-Boot, efi_uintn_t gets wrongly
interpreted as int, but it should actually be long in a 64-bit EFI
environment.
This changes the x86 __kernel_size_t conditionals to use compiler
provided defines instead. That way we always adhere to the build
environment we're in and the definitions adjust automatically.
Fixes: bb0bb91cf0aa ("efi_stub: Use efi_uintn_t") Signed-off-by: Bin Meng <bmeng.cn@gmail.com> Reviewed-by: Simon Glass <sjg@chromium.org>
Alexander Graf [Fri, 22 Jun 2018 08:38:26 +0000 (01:38 -0700)]
efi.h: Do not use config options
Currently efi.h determines a few bits of its environment according to
config options. This falls apart with the efi stub support which may
result in efi.h getting pulled into the stub as well as real U-Boot
code. In that case, one may be 32bit while the other one is 64bit.
This patch changes the conditionals to use compiler provided defines
instead. That way we always adhere to the build environment we're in
and the definitions adjust automatically.
Signed-off-by: Alexander Graf <agraf@suse.de> Reviewed-by: Bin Meng <bmeng.cn@gmail.com> Tested-by: Bin Meng <bmeng.cn@gmail.com>
[bmeng: added some comments to describe the __x86_64__ check] Signed-off-by: Bin Meng <bmeng.cn@gmail.com> Reviewed-by: Simon Glass <sjg@chromium.org>
Bin Meng [Sun, 17 Jun 2018 12:57:53 +0000 (05:57 -0700)]
x86: efi-x86_payload: Enable usb keyboard during boot
For boards that don't route serial port pins out, it's quite common
to attach a USB keyboard as the input device, along with a monitor.
However USB is not automatically started in the generic efi payload
codes. This uses a payload specific last_stage_init() to start the
USB bus, so that a USB keyboard can be used on the U-Boot shell.
Signed-off-by: Bin Meng <bmeng.cn@gmail.com> Reviewed-by: Simon Glass <sjg@chromium.org>
Bin Meng [Sun, 17 Jun 2018 12:57:52 +0000 (05:57 -0700)]
x86: efi-x86_payload: Enumerate PCI bus during early boot
The generic efi payload currently does not enumerate the PCI bus,
which means peripherals on the PCI bus are not discovered by their
drivers. This uses board_early_init_r() to do the PCI enumeration.
Signed-off-by: Bin Meng <bmeng.cn@gmail.com> Reviewed-by: Simon Glass <sjg@chromium.org>
Bin Meng [Sun, 17 Jun 2018 12:57:50 +0000 (05:57 -0700)]
board_r: Do not initialize IDE when DM BLK is on
With driver model philosophy, we should avoid explicitly calling
driver initialization routine during boot. This updates the ram
init sequence table to exclude the IDE initialization for DM BLK.
Signed-off-by: Bin Meng <bmeng.cn@gmail.com> Reviewed-by: Simon Glass <sjg@chromium.org>
Bin Meng [Sun, 17 Jun 2018 12:57:49 +0000 (05:57 -0700)]
x86: qemu: Change default vesa mode to 1024x768x32
The default vesa mode was changed since commit 55b4e1b7d999
("x86: Change default FRAMEBUFFER_VESA_MODE of some boards") for
better VxWorks compatibility but with the changes QEMU video console
no longer works. This is because QEMU's vgabios implements the VESA
mode 8:8:8 as 24bpp without an alpha channel, which U-Boot's video
console driver currently does not support yet.
We need change to real 32bpp in order to make it work again. QEMU
vgabios implements the custom 32bpp VESA mode starting from 0x140
(320x200x32) to 0x147 (1600x1200x32). Set it to 0x144 (1024x768x32).
Fixes: 55b4e1b7d999 ("x86: Change default FRAMEBUFFER_VESA_MODE of some boards") Signed-off-by: Bin Meng <bmeng.cn@gmail.com> Reviewed-by: Simon Glass <sjg@chromium.org>
Chris Packham [Thu, 7 Jun 2018 08:45:06 +0000 (20:45 +1200)]
patman: add option for limiting the Cc list
Many mailing-lists consider a long Cc list a sign of spam and will
either drop the message or mark it for moderation. Because patman
automatically invokes get_maintainer.pl the Cc list can expand
unexpectedly. Allow the user to specify a limit for the Cc list.
This limit is applied after removing any known bouncing addresses. By
default no limit is applied.
Signed-off-by: Chris Packham <judge.packham@gmail.com> Reviewed-by: Simon Glass <sjg@chromium.org>
Masahiro Yamada [Tue, 19 Jun 2018 07:11:45 +0000 (16:11 +0900)]
serial: uniphier: set clock rate without clock-frequency property
In Linux, the clock rate of the UART is given by the clock driver.
If you try to follow that in U-Boot, you would end up with adding
more u-boot,dm-pre-reloc properties, and also the clock driver would
be too big for SPL, which is used for UniPhier ARMv7 platform.
The current solution is to add 'clock-frequency' property to the
UART nodes, but it does not exist in the DT files in Linux. I do
not want to let DT diverge for U-Boot.
Check the SoC compatible and set the clock rate according to it.
This will be helpful to sync DT between Linux and U-Boot.
Masahiro Yamada [Tue, 19 Jun 2018 07:11:42 +0000 (16:11 +0900)]
ARM: uniphier: enable CONFIG_SNI_AVE and disable CONFIG_SMC911X
Enable the on-chip ethernet driver for uniphier_{v7,v8}_defconfig.
Disable the on-board SMC911x because it has not migrated to the
driver model yet - it is not possible to enable DM and non-DM
drivers at the same time.
The CONFIG_SMC911X for uniphier_ld4_sld8_defconfig is still kept
because the on-chip ethernet driver for LD4, sLD8 is not supported
yet.
Tom Rini [Fri, 22 Jun 2018 12:14:49 +0000 (08:14 -0400)]
Merge tag 'signed-efi-2018.07' of git://github.com/agraf/u-boot
Patch queue for efi - 2018-06-21
A single urgent fix to make sure green and red are not swapped
in OSs that make use of EFI GOP frame buffers to display pictures
(such as efifb in Linux).
Alexander Graf [Tue, 19 Jun 2018 11:34:54 +0000 (13:34 +0200)]
efi_loader: Fix GOP 32bpp exposure
We store pixels as BGRA in memory, as can be seen from struct efi_gop_pixel.
So we need to expose the same format to UEFI payloads to actually have them
use the correct colors.
Reported-by: Fabian Vogt <fvogt@suse.com> Tested-by: Peter Robinson <pbrobinson@gmail.com> Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de> Signed-off-by: Alexander Graf <agraf@suse.de>
Tom Rini [Wed, 20 Jun 2018 03:53:54 +0000 (23:53 -0400)]
Makefile: Ensure we build with -std=gnu11
As many targets are now commonly built with gcc-6 or later (which
defaults to a newer C standard than older compilers), certain C
constructs are now being used as they produce more readable code. And
while all compilers that we support building with support the C11
standard (and GNU11) they do not default to that standard. Ensure that
we pass along -std=gnu11 when building.
Neil Armstrong [Thu, 14 Jun 2018 11:43:37 +0000 (13:43 +0200)]
adc: meson-saradc: fix regmap_init_mem call
The SARADC driver was merged after the following commit :
commit d35812368a59 ("regmap: change regmap_init_mem() to take ofnode instead udevice")
Thus breaking build, this patch fixes the regmap_init_mem accordingly.
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Michal Simek [Wed, 13 Jun 2018 06:56:31 +0000 (08:56 +0200)]
common: Fix cpu nr type which is always unsigned type
cpu_cmd() is reading cpu number via simple_strtoul() which is always
unsigned type.
Platform code implementations are not expecting that nr can be negative
and there is not checking in the code for that too.
This patch is using u32 type for cpu number to make sure that platform
code get proper value range.
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Marek Vasut [Wed, 13 Jun 2018 04:13:33 +0000 (06:13 +0200)]
bootm: Handle kernel_noload on arm64
The ARM64 has 2 MiB alignment requirement for the kernel. When using
fitImage, this requirement may by violated, the kernel will thus be
executed from unaligned address and fail to boot. Do what booti does
and run booti_setup() for kernel_noload images on arm64 to obtain a
suitable aligned address to which the image shall be relocated.
Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com> Cc: Bin Chen <bin.chen@linaro.org> Cc: Masahiro Yamada <yamada.masahiro@socionext.com> Cc: Tom Rini <trini@konsulko.com>
Marek Vasut [Wed, 13 Jun 2018 04:13:32 +0000 (06:13 +0200)]
ARM: image: Add option for ignoring ep bit 3
Add option to the booti_setup() which indicates to it that the caller
requires the image to be relocated to the beginning of the RAM and
that the information whether the image can be located anywhere in RAM
at 2 MiB aligned boundary or not is to be ignored. This is useful ie.
in case the Image is wrapped in another envelope, ie. fitImage and not
relocating it but moving it would corrupt the envelope.
Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com> Cc: Bin Chen <bin.chen@linaro.org> Cc: Masahiro Yamada <yamada.masahiro@socionext.com> Cc: Tom Rini <trini@konsulko.com> Reviewed-By: Bin Chen <bin.chen@linaro.org>
Simon Glass [Tue, 12 Jun 2018 06:04:59 +0000 (00:04 -0600)]
fdtgrep: Separate out checking of two allocations
The current code might succeed on the first allocation and fail on the
second. Separate the checks to avoid this problem.
Of course, free() will never fail and the chances that (when allocating
two small areas) one will succeed and one will fail are just as remote.
But this keeps coverity happy.
Reported-by: Coverity (CID: 131226) Signed-off-by: Simon Glass <sjg@chromium.org>
Simon Glass [Tue, 12 Jun 2018 06:04:58 +0000 (00:04 -0600)]
fdtgrep: Fix logic of free() in do_fdtgrep()
This loop never actually exits, but the way the code is written this is
not obvious. Add an explicit error check.
Reported-by: Coverity (CID: 131280) Signed-off-by: Simon Glass <sjg@chromium.org>
[trini: Add explicit init of region to NULL per LLVM warning] Signed-off-by: Tom Rini <trini@konsulko.com>
Marek Vasut [Mon, 18 Jun 2018 02:09:10 +0000 (04:09 +0200)]
ARM: dts: rmobile: Move the PHY reset GPIOs into PHY nodes
Both the RAVB and SH ether driver now support parsing the PHY reset
GPIOs from both the PHY nodes and the MAC nodes, move the reset GPIOs
back into the PHY nodes to minimize DT difference between U-Boot and
Linux.
Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com> Cc: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>
Marek Vasut [Mon, 18 Jun 2018 02:03:01 +0000 (04:03 +0200)]
net: sh_eth: Support reset GPIO both in mac and phy node
The recent DTs have the PHY reset GPIO in the PHY node rather than
the ethernet MAC node, support extracting the PHY reset GPIO info
from both the PHY node and ethernet MAC node.
Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com> Cc: Nobuhiro Iwamatsu <iwamatsu@nigauri.org> Cc: Joe Hershberger <joe.hershberger@ni.com>
Marek Vasut [Mon, 18 Jun 2018 02:02:15 +0000 (04:02 +0200)]
net: ravb: Support reset GPIO both in mac and phy node
The recent DTs have the PHY reset GPIO in the PHY node rather than
the ethernet MAC node, support extracting the PHY reset GPIO info
from both the PHY node and ethernet MAC node.
Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com> Cc: Nobuhiro Iwamatsu <iwamatsu@nigauri.org> Cc: Joe Hershberger <joe.hershberger@ni.com>
Marek Vasut [Mon, 18 Jun 2018 03:44:53 +0000 (05:44 +0200)]
net: ravb: Filter out supported PHY features
The RAVB only supports 100Full and 1000Full operation, it does not support
10Full or any Half-duplex modes. The PHY could still advertise those features
though, so filter out the PHY features accordingly.
Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com> Cc: Nobuhiro Iwamatsu <iwamatsu@nigauri.org> Cc: Joe Hershberger <joe.hershberger@ni.com>
Marek Vasut [Mon, 18 Jun 2018 07:35:45 +0000 (09:35 +0200)]
net: ravb: Do not shut down clock in start callback
Do not stop the clock in the start callback in case of failure, keep
them running to also keep the PHY running. The failure could be ie.
PHY failing to negotiate link and if the clock get shut down, another
attempt at bringing the link up would fail. The clock right now are
started in probe function and stopped in remove function, which is
the correct behavior.
Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com> Cc: Nobuhiro Iwamatsu <iwamatsu@nigauri.org> Cc: Joe Hershberger <joe.hershberger@ni.com>
Simon Glass [Tue, 12 Jun 2018 06:04:56 +0000 (00:04 -0600)]
console: Fix handling of NULL global_data
Both putc() and puts() can be called before global_data is set up. Some of
the code paths don't handle this correctly. Add an explicit test before
any member is accessed.
Reported-by: Coverity (CID: 169030) Signed-off-by: Simon Glass <sjg@chromium.org> Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Adam Ford [Tue, 12 Jun 2018 01:05:38 +0000 (20:05 -0500)]
gpio: omap_gpio: Name GPIO's by bank and index with DM_GPIO
There are multiple GPIO banks with up to 32 pins / bank. When
using 'gpio status -a' to read the pins, this patch displays
both GPIO<bank>_<index> similar to how the device trees
display in addition to displaying gpio_#
Adam Ford [Tue, 12 Jun 2018 00:56:49 +0000 (19:56 -0500)]
arm: mach-omap2/omap3/clock.c: Enable all GPIO with CMD_GPIO
When CMD_GPIO is enabled the command 'gpio status -a' can cause
a hang or reboot if GPIO banks are not enabled, because it scans
all banks. This patch enables all GPIO banks so 'gpio status -a'
can fully execute.
Adam Ford [Mon, 11 Jun 2018 22:17:48 +0000 (17:17 -0500)]
block: Add SPL_BLOCK_CACHE and default n
When enabling BLOCK_CACHE on devices with limited RAM during SPL,
some devices may not boot. This creates an option to enable
block caching in SPL by defaults off. It is dependent on SPL_BLK
Fixes: 46960ad6d09b ("block: Have BLOCK_CACHE default to y in some cases") Signed-off-by: Adam Ford <aford173@gmail.com>
Andrew F. Davis [Mon, 11 Jun 2018 19:04:17 +0000 (14:04 -0500)]
arm: Do not clear LR on exception in SPL
When an exception or interrupt occurs the link register (LR) may
contain the source of the exception, although we do not print the
value it may still be extracted with a debugger. When in SPL we
loop on getting and exception, but use a linking branch, which
over-writes the LR value, use a regular branch instruction here.
Yevgeny Popovych [Mon, 11 Jun 2018 11:14:33 +0000 (14:14 +0300)]
fs: btrfs: Do not fail when all root_backups are empty
This is the case when reading freshly created filesystem.
The error message is like the following:
btrfs_read_superblock: No valid root_backup found!
Since the data from super_roots/root_backups is not actually used -
decided to rework btrfs_newest_root_backup() into
btrfs_check_super_roots() that will only check if super_roots
array is valid and correctly handle empty scenario.
As a result:
* btrfs_read_superblock() now only checks if super_roots array is valid;
the case when it is empty is considered OK.
* removed root_backup pointer from btrfs_info,
which would be NULL in case of empty super_roots.
* btrfs_read_superblock() verifies number of devices from the superblock
itself, not newest root_backup.
projects / u-boot / log