Rather than everyone writing their own adhoc device operation
NOP shim, we provide some formalism. We later make use of this
to reduce the loc count down trivially.
Change-Id: I2d04bfb50e76f367a0ee258dab97d7caa12ec99e
Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Reviewed-on: http://review.coreboot.org/7283
Tested-by: build bot (Jenkins)
Reviewed-by: Bruce Griffith <Bruce.Griffith@se-eng.com>
On the ASRock E350M1 a Nuvoton NCT5572D is used as SuperIO-chip. The coreboot
port to this board however used the driver of the Winbond W83627HF SuperIO,
which is compatible enough to get most stuff working, but which clears bit 6 in
register 0x2B. This switches the function of pin 38 of the NCT5572D from
RSTOUT1# output to GP36. The PERST# pin of the ethernet chip and the
unpopulated miniPCIe slot are connected to this pin, so they didn't get reset
during a reboot.
Using the newly added driver for the Nuvoton NCT5572D fixes this problem.
There is also a trace from the pin 37 of the SuperIO, which can be configured
as RSTOUT2#, to pin 82 of the USB3-chip with unknown function.
As with the wrong driver, PS/2 keyboard and mouse do work in SeaBIOS and GRUB
but not in Linux.
Change-Id: I4bc78406afd3b0e10a1b04b561147e0ed94cc494
Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Reviewed-on: http://review.coreboot.org/6266
Reviewed-by: Nicolas Reinecke <nr@das-labor.org>
Tested-by: build bot (Jenkins)
Reviewed-by: Nico Huber <nico.h@gmx.de>
Add support for both NCT6776D and NCT6776F devices.
Change-Id: If6686ea0a1cd6be537e286699b4ee8f88ba8ad7c
Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Reviewed-on: http://review.coreboot.org/5450
Tested-by: build bot (Jenkins)
Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Change-Id: I3b720cf879bf5326be885d2d3a3f9cfba0a27c7e
Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Reviewed-on: http://review.coreboot.org/6229
Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Reviewed-by: Nicolas Reinecke <nr@das-labor.org>
Tested-by: build bot (Jenkins)
This patch adds the 10ms TRSTRCY delay between a reset and the following
Set Address command that is required by the USB 2.0 specification to the
EHCI root hub driver. The generic_hub driver that's used for XHCI and
external hubs already included this delay. This is such a glaring
violation of the spec that I'm really amazed how many USB 2.0 devices
we tested before seemed perfectly fine with responding to a Set Address
within 2 microframes of the reset...
It also increases the port reset hold delay by one millisecond to avoid
an ugly race condition on Tegra SoCs: they decided to time the 50ms
themselves instead of relying on the CPU to do it (fair enough), and to
automatically transition Port Reset to 0 and Port Enable to 1 after that
(bad idea). If the CPU's read-modify-write to clear Port Reset races
exactly with the host controller setting Port Enable, we may end up
clearing the bit again and going into the companion controller handoff
path later on. The added millisecond shouldn't cause any problems for
other host controllers and is not a big deal compared to other delays in
this code path.
BUG=chrome-os-partner:26749
TEST=Run several dozen reboot loops with The USB Stick of Death (TM) (a
blue Patriot XT 13fe:5200 with bcdDevice = 1.00), make sure it always
gets detected correctly.
Original-Change-Id: Idd3329ae6d7e5e1c07a84a5475549b3459836b31
Original-Signed-off-by: Julius Werner <jwerner@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/189872
Original-Reviewed-by: Gabe Black <gabeblack@chromium.org>
Original-Reviewed-by: Jim Lin <jilin@nvidia.com>
Original-Reviewed-by: Hung-Te Lin <hungte@chromium.org>
(cherry picked from commit 4deca38e9d79f6373f4418fcaf51a6945232c8b8)
Signed-off-by: Marc Jones <marc.jones@se-eng.com>
Change-Id: I68a29bfd2e0f30409fbfc330b2575f0f9f61a79d
Reviewed-on: http://review.coreboot.org/7221
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Fix a warning when using gcc:
i386-elf-gcc: error: unrecognized command line option
'-print-librt-file-name'
Change-Id: I421933ede9ddbddad37544a62e428c79e9ee2c8d
Signed-off-by: Martin Roth <martin.roth@se-eng.com>
Reviewed-on: http://review.coreboot.org/7249
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Tested-by: build bot (Jenkins)
Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Minnowboard Max was broken by
commit 454625c5 - intel/fsp_baytrail: Fix SMM/SMI
because TSEG wasn't set to 8MB by the FSP.
The default in the FSP is 1MB.
Change-Id: I2e671a6ca0240e931399920c62439c36133789aa
Signed-off-by: Martin Roth <martin.roth@se-eng.com>
Reviewed-on: http://review.coreboot.org/7240
Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Tested-by: build bot (Jenkins)
Correct mask to select bits 4-6 inclusively as per comment and use
bitwise operations while working with bits. Be sure to write back out
the data on the retrain.
Change-Id: I26e7acddbff32e978c2bf984c21d9a63337067f8
Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Found-by: Clang
Reviewed-on: http://review.coreboot.org/6147
Reviewed-by: Marc Jones <marc.jones@se-eng.com>
Tested-by: build bot (Jenkins)
Following the reasoning in,
8089f17 mainboard/lenovo/x230 Fix usage of GNU field designator extension
In C99 we defined a syntax for this. GCC's old syntax was deprecated.
Change-Id: I167d2c9ad3f690de41fee51dd7800ce76b328e41
Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Reviewed-on: http://review.coreboot.org/7231
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Tested-by: build bot (Jenkins)
Currently clang/llvm builds are not fully supported. As such,
let us tone down treating errors as warnings until we actually
build the entire tree.
Change-Id: If7f90f9887e27250f5e6d73d1692505676be9d47
Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Reviewed-on: http://review.coreboot.org/7230
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Tested-by: build bot (Jenkins)
Following the reasoning in,
8089f17 mainboard/lenovo/x230 Fix usage of GNU field designator extension
In C99 we defined a syntax for this. GCC's old syntax was deprecated.
Change-Id: Id5c5d68048169b0cd400926cead2d1835194d1a5
Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Reviewed-on: http://review.coreboot.org/7210
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Following the reasoning in,
8089f17 mainboard/lenovo/x230 Fix usage of GNU field designator extension
In C99 we defined a syntax for this. GCC's old syntax was deprecated.
Change-Id: Ibbcdbb44c7586ac8d445870789647f8ff9585452
Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Reviewed-on: http://review.coreboot.org/7232
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Tested-by: build bot (Jenkins)
This is a copy of the tool provided by the vendor. It adds a
header which tells the early stage loader where to load the next phase
blob for execution. It is going to be used to encapsulate the
bootblock.
Usage of this tool is as follows:
ipqheader.py <base-addr> <input-file> <output-file>
Old-Change-Id: I448c006719f4f3dd5a6716ff2e47f7fc275c805e
Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/193494
Reviewed-by: Furquan Shaikh <furquan@chromium.org>
Reviewed-by: Stefan Reinauer <reinauer@chromium.org>
(cherry picked from commit 201630f8637eb627f0894ecd7bceb31017244ad4)
Make ipqheader.py executable
Modify the utility to become a Linux executable. While at it, fix the
program name reported by error messages.
Old-Change-Id: I25061d43fdea72655a696deb9e494e9c7382f670
Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/193495
Reviewed-by: Furquan Shaikh <furquan@chromium.org>
Reviewed-by: Stefan Reinauer <reinauer@chromium.org>
(cherry picked from commit bbbf69c754aa3b6a1bf17ab3ced1c739c3ee0688)
ipq8064: SBL headers must have 4 byte aligned blob sizes
It turns out that for SBL3 to load the next phase, the sizes in the
MBN header must be 4 byres aligned. This change makes sure that this
requirement is enforced.
Old-Change-Id: Ia64f04bb281ae772b060d2f7713c98dd348972ba
Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/196167
(cherry picked from commit fa6a52a07cb87ecf2538a6b0d47605d79104e4cc)
Add proper license to the ipqheader tool
This patch adds a vanilla BSD 3-Clause license.
Original-Change-Id: I9da7176e670b598808ef5be2461b6105a4c5f6c5
Original-Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/225783
Original-Reviewed-by: Trevor Bourget <tbourget@codeaurora.org>
Original-Tested-by: Trevor Bourget <tbourget@codeaurora.org>
Original-Reviewed-by: David Hendricks <dhendrix@chromium.org>
(cherry picked from commit a0c47a8d74f1ac131c91e978b6d68bbcfaa52c37)
Squashed 4 commits for the ipqheader util.
Change-Id: I144c01947a89e1348a06aa82590e972e2ec31247
Signed-off-by: Isaac Christensen <isaac.christensen@se-eng.com>
Signed-off-by: Marc Jones <marc.jones@se-eng.com>
Reviewed-on: http://review.coreboot.org/6976
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Tested-by: build bot (Jenkins)
Add support for creating ARM rmodules. There are 3 expected
relocations for an ARM rmodule:
- R_ARM_ABS32
- R_ARM_THM_PC22
- R_ARM_THM_JUMP24
R_ARM_ABS32 is the only type that needs to emitted for relocation
as the other 2 are relative relocations.
BUG=chrome-os-partner:27094
BRANCH=None
TEST=Built vbootstub for ARM device.
Original-Change-Id: I0c22d4abca970e82ccd60b33fed700b96e3e52fb
Original-Signed-off-by: Aaron Durbin <adurbin@chromuim.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/190922
Original-Reviewed-by: Gabe Black <gabeblack@chromium.org>
(cherry picked from commit a642102ba7ace5c1829abe7732199eda6646950a)
Signed-off-by: Marc Jones <marc.jones@se-eng.com>
Change-Id: Ib3b3c90ebb672d8d6a537df896b97dc82c6186cc
Reviewed-on: http://review.coreboot.org/7204
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
With following settings
1.Coreboot 25Mhz
2.Maxim codec configured with MCLK=25Mhz
2.I2C 400Khz fixed
4.Including Enable/Disable SHDN bit when LRCLK starts/Stops
5.Removed PLL toggle workaround routine.
audio playing is smooth before/after S3, no noise when recording so change
MCLK from 19.2 back to 25Mhz.
BUG=chrome-os-partner:26948
BRANCH=firmware-rambi-5216
TEST=test audio play and record on Rambi, works fine.
Change-Id: I5602feb39721344feab837ff4a3a18309a47a6a6
Signed-off-by: Kein Yuan <kein.yuan@intel.com>
Reviewed-on: https://chromium-review.googlesource.com/193881
Tested-by: Shawn Nematbakhsh <shawnn@chromium.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Commit-Queue: Shawn Nematbakhsh <shawnn@chromium.org>
(cherry picked from commit bfe1d535aa2f20a32e163abeb99f3d657e2b43ab)
Signed-off-by: Marc Jones <marc.jones@se-eng.com>
Reviewed-on: http://review.coreboot.org/7219
Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Tested-by: build bot (Jenkins)
- The hotplug register doesn't work in the way we describe. Just leave
it at default.
- The backlight registers will be configured by the OS driver.
BUG=chrome-os-partner:27304
TEST=Manual on Rambi. Boot system in both dev and normal mode, verify
that display comes up. Also verify that display functions after warm
reboot and suspend / resume.
BRANCH=rambi+squawks
Change-Id: I5559c131f41c4a14e64e5cec66e18d3a4a46092c
Signed-off-by: Shawn Nematbakhsh <shawnn@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/193830
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
(cherry picked from commit 3f287cc31e41fabef755c37361e2e65ca413c88c)
Signed-off-by: Marc Jones <marc.jones@se-eng.com>
Reviewed-on: http://review.coreboot.org/7217
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
bit: 7 6 5 4 3 2 1 0
LFP2 EFP2 EFP3 CRT2 LFP EFP TV CRT
so int 15 0x5f35 need to return 0x8(LFP/eDP) instead of 0x2(TV).
BUG=chrome-os-partner:26365
BUG=chrome-os-partner:27505
BRANCH=rambi
TEST=Booted with and without HDMI connected monitor. DEV screen
always showed on eDP panel on Rambi.
Change-Id: I8f876e78383424f517689eb25e9229a27739957b
Original-Change-Id: I77edbeb3c86549f90302b4296b5a2f50313ca675
Signed-off-by: Kein Yuan <kein.yuan@intle.com>
Reviewed-on: https://chromium-review.googlesource.com/193303
Commit-Queue: Shawn Nematbakhsh <shawnn@chromium.org>
Tested-by: Shawn Nematbakhsh <shawnn@chromium.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
(cherry picked from commit dd375462147f182331f336ba826108e58b4e0a47)
Signed-off-by: Marc Jones <marc.jones@se-eng.com>
Reviewed-on: http://review.coreboot.org/7216
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Provide the option to embed MRC as an ELF file and not just
binary blob. This allows for MRC to be relocated.
BUG=chrome-os-partner:27654
BRANCH=rambi
TEST=Built and booted rambi.
Change-Id: I2e177c155a3074e4e1d450b1a73b7299aebd5286
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/192893
Reviewed-by: Duncan Laurie <dlaurie@chromium.org>
(cherry picked from commit 89c97d5e2023b8c5cc780e1b1d532d0a586512f9)
Signed-off-by: Marc Jones <marc.jones@se-eng.com>
Reviewed-on: http://review.coreboot.org/7214
Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Tested-by: build bot (Jenkins)
Moving the cache-as-ram base address to 0xfe000000 will
provide more breathing room in the physical address space.
It will also allow for larger SPI roms in the future.
BUG=chrome-os-partner:27045
BRANCH=baytrail
CQ-DEPEND=CL:*157278
TEST=Built and booted. Suspended and resumes. Vboot works, MRC
settings are being saved as well.
Change-Id: I618c069e504f545e02de5ac54e057566f0b5d6c9
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/190700
Reviewed-by: Bernie Thompson <bhthompson@chromium.org>
Reviewed-by: Duncan Laurie <dlaurie@chromium.org>
(cherry picked from commit 73c07a319d678f3e9be2fac64599c94f91c9ad9c)
Signed-off-by: Marc Jones <marc.jones@se-eng.com>
Reviewed-on: http://review.coreboot.org/7212
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Implement vboot_get_sw_write_protect, which returns the FW SPI ROM SW WP
status.
BUG=chrome-os-partner:26777
TEST=Manual on Rambi with all patches in sequence:
`crossystem sw_wpsw_boot` prints 0
`flashrom --wp-enable` + reboot
`crossystem sw_wpsw_boot` prints 1
BRANCH=Rambi
Original-Change-Id: I5da35c1b2d25b8679bf0084af65d08de224387f8
Original-Signed-off-by: Shawn Nematbakhsh <shawnn@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/190097
Original-Reviewed-by: Aaron Durbin <adurbin@chromium.org>
(cherry picked from commit 5bba447654417c42952c49542ed047b4867d04d1)
Signed-off-by: Marc Jones <marc.jones@se-eng.com>
Change-Id: I739cbb8fca5f02462cf78c81f9b364aabfd3fe86
Reviewed-on: http://review.coreboot.org/7211
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
The LZMA compression algorithm, currently the only one available, will fail
if you ask it to write more data to the output than you've given it space for.
The code that calls into LZMA allocates an output buffer the same size as the
input, so if compression increases the size of the output the call will fail.
The caller(s) were written to assume that the call succeeded and check the
returned length to see if the size would have increased, but that will never
happen with LZMA.
Rather than try to rework the LZMA library to dynamically resize the output
buffer or try to guess what the maximal size the data could expand to is, this
change makes the caller simply print a warning and disable compression if the
call failed for some reason.
This may lead to images that are larger than necessary if compression fails
for some other reason and the user doesn't notice, but since compression
errors were ignored entirely until very recently that will hopefully not be
a problem in practice, and we should be guaranteed to at least produce a
correct image.
Original-Change-Id: I5f59529c2d48e9c4c2e011018b40ec336c4fcca8
Original-Signed-off-by: Gabe Black <gabeblack@google.com>
Original-Reviewed-on: https://chromium-review.googlesource.com/187365
Original-Reviewed-by: David Hendricks <dhendrix@chromium.org>
Original-Tested-by: Gabe Black <gabeblack@chromium.org>
Original-Commit-Queue: Gabe Black <gabeblack@chromium.org>
(cherry picked from commit b9f622a554d5fb9a9aff839c64e11acb27785f13)
Signed-off-by: Isaac Christensen <isaac.christensen@se-eng.com>
Change-Id: I5f59529c2d48e9c4c2e011018b40ec336c4fcca8
Reviewed-on: http://review.coreboot.org/6958
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Ensure that the SMM build stage links properly using the compiler-rt
runtime under a Clang build.
Change-Id: Iead28c46d63f5bbb27757b7dc66fe06b4813d03c
Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Reviewed-on: http://review.coreboot.org/6462
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Make use of '-print-librt-file-name' over '-print-libgcc-file-name'
to use Compiler-RT runtime glue over libgcc glue.
NOTE: *** Requires at least clang 3.6.x
Change-Id: I7f63284473d6067bf775409970c8dd98f5d5a8d5
Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Reviewed-on: http://review.coreboot.org/6144
Reviewed-by: Marc Jones <marc.jones@se-eng.com>
Tested-by: build bot (Jenkins)
Hiding pointer types behind 'typedef's is usually not a great
idea at the best of times. Worse the typedef becomes an integer
at different stages in Coreboot. Let us refrain from doing this
at all.
Change-Id: Ia2ca8c98bb489daaa58f379433875864f6efabc8
Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Reviewed-on: http://review.coreboot.org/7136
Tested-by: build bot (Jenkins)
Reviewed-by: Nico Huber <nico.h@gmx.de>
The romstage component of Super I/O support is in fact written around
passing a lower and upper half packed integer. We currently have two
typedef's for this, 'device_t' and 'pnp_devfn_t'. We wish to make use of
'pnp_devfn_t' over 'device_t' as 'device_t' changes it's typedef in the
ramstage context and so is really a conflicting definition. This helps
solve problems down the road to having the 'real' 'device_t' definition
usable in romstage later.
This follows on from the rational given in:
c2956e7 device/pci_early.c: Mixes up variants of a typedefs to 'u32'
Change-Id: Ia9f238ebb944f9fe7b274621ee0c09a6de288a76
Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Reviewed-on: http://review.coreboot.org/6231
Reviewed-by: Nico Huber <nico.h@gmx.de>
Tested-by: build bot (Jenkins)
'pci_devfn_t' and 'pnp_devfn_t' are already defined in arch/io.h
Change-Id: I006182bf6933fae21fe6671659b76e7031e74b71
Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Reviewed-on: http://review.coreboot.org/6230
Reviewed-by: Nico Huber <nico.h@gmx.de>
Tested-by: build bot (Jenkins)
Part number is used only for coreboot ROM identification and
in coreboot tables. Rather than guessing the P/N, just use readable name.
SMBIOS uses information from EEPROM and so isn't affected.
Change-Id: I33534c3acb83f20d5b493c82bfc98896bf64ff1a
Signed-off-by: Vladimir Serbinenko <phcoder@gmail.com>
Reviewed-on: http://review.coreboot.org/7177
Reviewed-by: Nico Huber <nico.h@gmx.de>
Tested-by: build bot (Jenkins)
The simo board with console output at UART port 1 (COM2) will not produce
any output if CONFIG_UART_FOR_CONSOLE=1 is set correctly.
Commit f29200240e
(superio/ite/*: Factor out generic romstage component)
will only and always activate UART port 0 unregarded to
CONFIG_UART_FOR_CONSOLE value.
Now the UART port which was selected by CONFIG_UART_FOR_CONSOLE
will be enabled and used for console output
Change-Id: Ibbd2b5115b1ed4763962ba32fc9c19431a906c78
Signed-off-by: Dennis Wassenberg <dennis.wassenberg@secunet.com>
Reviewed-on: http://review.coreboot.org/7060
Tested-by: build bot (Jenkins)
Reviewed-by: Nico Huber <nico.h@gmx.de>
IMC fan control should be enabled after OS launched.
I have tested on OliveHill and Parmer with Windows 7 and Ubuntu 13.10.
Change-Id: I16d6ff6b1272d16b840e803e0a95f6e363c79704
Signed-off-by: WANG Siyuan <SiYuan.Wang@amd.com>
Signed-off-by: WANG Siyuan <wangsiyuanbuaa@gmail.com>
Reviewed-on: http://review.coreboot.org/7165
Tested-by: build bot (Jenkins)
Reviewed-by: Bruce Griffith <Bruce.Griffith@se-eng.com>
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Edward O'Callaghan