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u-boot/doc/README.POST
Tom Rini 1e01950333 post: Move CONFIG_SYS_POST to CFG_SYS_POST 
Migrate the rest of the CONFIG_SYS_POST macros over to CFG_SYS_POST
namespace.

Signed-off-by: Tom Rini <trini@konsulko.com>
2022-12-23 13:01:13 -05:00

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Power-On-Self-Test support in U-Boot
------------------------------------
This project is to support Power-On-Self-Test (POST) in U-Boot.
1. High-level requirements
The key requirements for this project are as follows:
1) The project shall develop a flexible framework for implementing
and running Power-On-Self-Test in U-Boot. This framework shall
possess the following features:
o) Extensibility
The framework shall allow adding/removing/replacing POST tests.
Also, standalone POST tests shall be supported.
o) Configurability
The framework shall allow run-time configuration of the lists
of tests running on normal/power-fail booting.
o) Controllability
The framework shall support manual running of the POST tests.
2) The results of tests shall be saved so that it will be possible to
retrieve them from Linux.
3) The following POST tests shall be developed for MPC823E-based
boards:
o) CPU test
o) Cache test
o) Memory test
o) Ethernet test
o) Serial channels test
o) Watchdog timer test
o) RTC test
o) I2C test
o) SPI test
o) USB test
4) The LWMON board shall be used for reference.
2. Design
This section details the key points of the design for the project.
The whole project can be divided into two independent tasks:
enhancing U-Boot/Linux to provide a common framework for running POST
tests and developing such tests for particular hardware.
2.1. Hardware-independent POST layer
A new optional module will be added to U-Boot, which will run POST
tests and collect their results at boot time. Also, U-Boot will
support running POST tests manually at any time by executing a
special command from the system console.
The list of available POST tests will be configured at U-Boot build
time. The POST layer will allow the developer to add any custom POST
tests. All POST tests will be divided into the following groups:
1) Tests running on power-on booting only
This group will contain those tests that run only once on
power-on reset (e.g. watchdog test)
2) Tests running on normal booting only
This group will contain those tests that do not take much
time and can be run on the regular basis (e.g. CPU test)
3) Tests running in special "slow test mode" only
This group will contain POST tests that consume much time
and cannot be run regularly (e.g. strong memory test, I2C test)
4) Manually executed tests
This group will contain those tests that can be run manually.
If necessary, some tests may belong to several groups simultaneously.
For example, SDRAM test may run in both normal and "slow test" mode.
In normal mode, SDRAM test may perform a fast superficial memory test
only, while running in slow test mode it may perform a full memory
check-up.
Also, all tests will be discriminated by the moment they run at.
Specifically, the following groups will be singled out:
1) Tests running before relocating to RAM
These tests will run immediately after initializing RAM
as to enable modifying it without taking care of its
contents. Basically, this group will contain memory tests
only.
2) Tests running after relocating to RAM
These tests will run immediately before entering the main
loop as to guarantee full hardware initialization.
The POST layer will also distinguish a special group of tests that
may cause system rebooting (e.g. watchdog test). For such tests, the
layer will automatically detect rebooting and will notify the test
about it.
2.1.1. POST layer interfaces
This section details the interfaces between the POST layer and the
rest of U-Boot.
The following flags will be defined:
#define POST_POWERON 0x01 /* test runs on power-on booting */
#define POST_NORMAL 0x02 /* test runs on normal booting */
#define POST_SLOWTEST 0x04 /* test is slow, enabled by key press */
#define POST_POWERTEST 0x08 /* test runs after watchdog reset */
#define POST_ROM 0x100 /* test runs in ROM */
#define POST_RAM 0x200 /* test runs in RAM */
#define POST_MANUAL 0x400 /* test can be executed manually */
#define POST_REBOOT 0x800 /* test may cause rebooting */
#define POST_PREREL 0x1000 /* test runs before relocation */
The POST layer will export the following interface routines:
o) int post_run(struct bd_info *bd, char *name, int flags);
This routine will run the test (or the group of tests) specified
by the name and flag arguments. More specifically, if the name
argument is not NULL, the test with this name will be performed,
otherwise all tests running in ROM/RAM (depending on the flag
argument) will be executed. This routine will be called at least
twice with name set to NULL, once from board_init_f() and once
from board_init_r(). The flags argument will also specify the
mode the test is executed in (power-on, normal, power-fail,
manual).
o) void post_reloc(ulong offset);
This routine will be called from board_init_r() and will
relocate the POST test table.
o) int post_info(char *name);
This routine will print the list of all POST tests that can be
executed manually if name is NULL, and the description of a
particular test if name is not NULL.
o) int post_log(char *format, ...);
This routine will be called from POST tests to log their
results. Basically, this routine will print the results to
stderr. The format of the arguments and the return value
will be identical to the printf() routine.
Also, the following board-specific routines will be called from the
U-Boot common code:
o) int post_hotkeys_pressed(gd_t *gd)
This routine will scan the keyboard to detect if a magic key
combination has been pressed, or otherwise detect if the
power-on long-running tests shall be executed or not ("normal"
versus "slow" test mode).
The list of available POST tests be kept in the post_tests array
filled at U-Boot build time. The format of entry in this array will
be as follows:
struct post_test {
char *name;
char *cmd;
char *desc;
int flags;
int (*test)(struct bd_info *bd, int flags);
};
o) name
This field will contain a short name of the test, which will be
used in logs and on listing POST tests (e.g. CPU test).
o) cmd
This field will keep a name for identifying the test on manual
testing (e.g. cpu). For more information, refer to section
"Command line interface".
o) desc
This field will contain a detailed description of the test,
which will be printed on user request. For more information, see
section "Command line interface".
o) flags
This field will contain a combination of the bit flags described
above, which will specify the mode the test is running in
(power-on, normal, power-fail or manual mode), the moment it
should be run at (before or after relocating to RAM), whether it
can cause system rebooting or not.
o) test
This field will contain a pointer to the routine that will
perform the test, which will take 2 arguments. The first
argument will be a pointer to the board info structure, while
the second will be a combination of bit flags specifying the
mode the test is running in (POST_POWERON, POST_NORMAL,
POST_SLOWTEST, POST_MANUAL) and whether the last execution of
the test caused system rebooting (POST_REBOOT). The routine will
return 0 on successful execution of the test, and 1 if the test
failed.
The lists of the POST tests that should be run at power-on/normal/
power-fail booting will be kept in the environment. Namely, the
following environment variables will be used: post_poweron,
powet_normal, post_slowtest.
2.1.2. Test results
The results of tests will be collected by the POST layer. The POST
log will have the following format:
...
--------------------------------------------
START <name>
<test-specific output>
[PASSED|FAILED]
--------------------------------------------
...
Basically, the results of tests will be printed to stderr. This
feature may be enhanced in future to spool the log to a serial line,
save it in non-volatile RAM (NVRAM), transfer it to a dedicated
storage server and etc.
2.1.3. Integration issues
All POST-related code will be #ifdef'ed with the CONFIG_POST macro.
This macro will be defined in the config_<board>.h file for those
boards that need POST. The CFG_POST macro will contain the list of
POST tests for the board. The macro will have the format of array
composed of post_test structures:
#define CFG_POST \
{
"On-board peripherals test", "board", \
" This test performs full check-up of the " \
"on-board hardware.", \
POST_RAM | POST_SLOWTEST, \
&board_post_test \
}
A new file, post.h, will be created in the include/ directory. This
file will contain common POST declarations and will define a set of
macros that will be reused for defining CFG_POST. As an example,
the following macro may be defined:
#define POST_CACHE \
{
"Cache test", "cache", \
" This test verifies the CPU cache operation.", \
POST_RAM | POST_NORMAL, \
&cache_post_test \
}
A new subdirectory will be created in the U-Boot root directory. It
will contain the source code of the POST layer and most of POST
tests. Each POST test in this directory will be placed into a
separate file (it will be needed for building standalone tests). Some
POST tests (mainly those for testing peripheral devices) will be
located in the source files of the drivers for those devices. This
way will be used only if the test subtantially uses the driver.
2.1.4. Standalone tests
The POST framework will allow to develop and run standalone tests. A
user-space library will be developed to provide the POST interface
functions to standalone tests.
2.1.5. Command line interface
A new command, diag, will be added to U-Boot. This command will be
used for listing all available hardware tests, getting detailed
descriptions of them and running these tests.
More specifically, being run without any arguments, this command will
print the list of all available hardware tests:
=> diag
Available hardware tests:
cache - cache test
cpu - CPU test
enet - SCC/FCC ethernet test
Use 'diag [<test1> [<test2>]] ... ' to get more info.
Use 'diag run [<test1> [<test2>]] ... ' to run tests.
=>
If the first argument to the diag command is not 'run', detailed
descriptions of the specified tests will be printed:
=> diag cpu cache
cpu - CPU test
This test verifies the arithmetic logic unit of CPU.
cache - cache test
This test verifies the CPU cache operation.
=>
If the first argument to diag is 'run', the specified tests will be
executed. If no tests are specified, all available tests will be
executed.
It will be prohibited to execute tests running in ROM manually. The
'diag' command will not display such tests and/or run them.
2.1.6. Power failure handling
The Linux kernel will be modified to detect power failures and
automatically reboot the system in such cases. It will be assumed
that the power failure causes a system interrupt.
To perform correct system shutdown, the kernel will register a
handler of the power-fail IRQ on booting. Being called, the handler
will run /sbin/reboot using the call_usermodehelper() routine.
/sbin/reboot will automatically bring the system down in a secure
way. This feature will be configured in/out from the kernel
configuration file.
The POST layer of U-Boot will check whether the system runs in
power-fail mode. If it does, the system will be powered off after
executing all hardware tests.
2.1.7. Hazardous tests
Some tests may cause system rebooting during their execution. For
some tests, this will indicate a failure, while for the Watchdog
test, this means successful operation of the timer.
In order to support such tests, the following scheme will be
implemented. All the tests that may cause system rebooting will have
the POST_REBOOT bit flag set in the flag field of the correspondent
post_test structure. Before starting tests marked with this bit flag,
the POST layer will store an identification number of the test in a
location in IMMR. On booting, the POST layer will check the value of
this variable and if it is set will skip over the tests preceding the
failed one. On second execution of the failed test, the POST_REBOOT
bit flag will be set in the flag argument to the test routine. This
will allow to detect system rebooting on the previous iteration. For
example, the watchdog timer test may have the following
declaration/body:
...
#define POST_WATCHDOG \
{
"Watchdog timer test", "watchdog", \
" This test checks the watchdog timer.", \
POST_RAM | POST_POWERON | POST_REBOOT, \
&watchdog_post_test \
}
...
...
int watchdog_post_test(struct bd_info *bd, int flags)
{
unsigned long start_time;
if (flags & POST_REBOOT) {
/* Test passed */
return 0;
} else {
/* disable interrupts */
disable_interrupts();
/* 10-second delay */
...
/* if we've reached this, the watchdog timer does not work */
enable_interrupts();
return 1;
}
}
...
2.2. Hardware-specific details
This project will also develop a set of POST tests for MPC8xx- based
systems. This section provides technical details of how it will be
done.
2.2.1. Generic PPC tests
The following generic POST tests will be developed:
o) CPU test
This test will check the arithmetic logic unit (ALU) of CPU. The
test will take several milliseconds and will run on normal
booting.
o) Cache test
This test will verify the CPU cache (L1 cache). The test will
run on normal booting.
o) Memory test
This test will examine RAM and check it for errors. The test
will always run on booting. On normal booting, only a limited
amount of RAM will be checked. On power-fail booting a fool
memory check-up will be performed.
2.2.1.1. CPU test
This test will verify the following ALU instructions:
o) Condition register istructions
This group will contain: mtcrf, mfcr, mcrxr, crand, crandc,
cror, crorc, crxor, crnand, crnor, creqv, mcrf.
The mtcrf/mfcr instructions will be tested by loading different
values into the condition register (mtcrf), moving its value to
a general-purpose register (mfcr) and comparing this value with
the expected one. The mcrxr instruction will be tested by
loading a fixed value into the XER register (mtspr), moving XER
value to the condition register (mcrxr), moving it to a
general-purpose register (mfcr) and comparing the value of this
register with the expected one. The rest of instructions will be
tested by loading a fixed value into the condition register
(mtcrf), executing each instruction several times to modify all
4-bit condition fields, moving the value of the conditional
register to a general-purpose register (mfcr) and comparing it
with the expected one.
o) Integer compare instructions
This group will contain: cmp, cmpi, cmpl, cmpli.
To verify these instructions the test will run them with
different combinations of operands, read the condition register
value and compare it with the expected one. More specifically,
the test will contain a pre-built table containing the
description of each test case: the instruction, the values of
the operands, the condition field to save the result in and the
expected result.
o) Arithmetic instructions
This group will contain: add, addc, adde, addme, addze, subf,
subfc, subfe, subme, subze, mullw, mulhw, mulhwu, divw, divwu,
extsb, extsh.
The test will contain a pre-built table of instructions,
operands, expected results and expected states of the condition
register. For each table entry, the test will cyclically use
different sets of operand registers and result registers. For
example, for instructions that use 3 registers on the first
iteration r0/r1 will be used as operands and r2 for result. On
the second iteration, r1/r2 will be used as operands and r3 as
for result and so on. This will enable to verify all
general-purpose registers.
o) Logic instructions
This group will contain: and, andc, andi, andis, or, orc, ori,
oris, xor, xori, xoris, nand, nor, neg, eqv, cntlzw.
The test scheme will be identical to that from the previous
point.
o) Shift instructions
This group will contain: slw, srw, sraw, srawi, rlwinm, rlwnm,
rlwimi
The test scheme will be identical to that from the previous
point.
o) Branch instructions
This group will contain: b, bl, bc.
The first 2 instructions (b, bl) will be verified by jumping to
a fixed address and checking whether control was transferred to
that very point. For the bl instruction the value of the link
register will be checked as well (using mfspr). To verify the bc
instruction various combinations of the BI/BO fields, the CTR
and the condition register values will be checked. The list of
such combinations will be pre-built and linked in U-Boot at
build time.
o) Load/store instructions
This group will contain: lbz(x)(u), lhz(x)(u), lha(x)(u),
lwz(x)(u), stb(x)(u), sth(x)(u), stw(x)(u).
All operations will be performed on a 16-byte array. The array
will be 4-byte aligned. The base register will point to offset
8. The immediate offset (index register) will range in [-8 ...
+7]. The test cases will be composed so that they will not cause
alignment exceptions. The test will contain a pre-built table
describing all test cases. For store instructions, the table
entry will contain: the instruction opcode, the value of the
index register and the value of the source register. After
executing the instruction, the test will verify the contents of
the array and the value of the base register (it must change for
"store with update" instructions). For load instructions, the
table entry will contain: the instruction opcode, the array
contents, the value of the index register and the expected value
of the destination register. After executing the instruction,
the test will verify the value of the destination register and
the value of the base register (it must change for "load with
update" instructions).
o) Load/store multiple/string instructions
The CPU test will run in RAM in order to allow run-time modification
of the code to reduce the memory footprint.
2.2.1.2 Special-Purpose Registers Tests
TBD.
2.2.1.3. Cache test
To verify the data cache operation the following test scenarios will
be used:
1) Basic test #1
- turn on the data cache
- switch the data cache to write-back or write-through mode
- invalidate the data cache
- write the negative pattern to a cached area
- read the area
The negative pattern must be read at the last step
2) Basic test #2
- turn on the data cache
- switch the data cache to write-back or write-through mode
- invalidate the data cache
- write the zero pattern to a cached area
- turn off the data cache
- write the negative pattern to the area
- turn on the data cache
- read the area
The negative pattern must be read at the last step
3) Write-through mode test
- turn on the data cache
- switch the data cache to write-through mode
- invalidate the data cache
- write the zero pattern to a cached area
- flush the data cache
- write the negative pattern to the area
- turn off the data cache
- read the area
The negative pattern must be read at the last step
4) Write-back mode test
- turn on the data cache
- switch the data cache to write-back mode
- invalidate the data cache
- write the negative pattern to a cached area
- flush the data cache
- write the zero pattern to the area
- invalidate the data cache
- read the area
The negative pattern must be read at the last step
To verify the instruction cache operation the following test
scenarios will be used:
1) Basic test #1
- turn on the instruction cache
- unlock the entire instruction cache
- invalidate the instruction cache
- lock a branch instruction in the instruction cache
- replace the branch instruction with "nop"
- jump to the branch instruction
- check that the branch instruction was executed
2) Basic test #2
- turn on the instruction cache
- unlock the entire instruction cache
- invalidate the instruction cache
- jump to a branch instruction
- check that the branch instruction was executed
- replace the branch instruction with "nop"
- invalidate the instruction cache
- jump to the branch instruction
- check that the "nop" instruction was executed
The CPU test will run in RAM in order to allow run-time modification
of the code.
2.2.1.4. Memory test
The memory test will verify RAM using sequential writes and reads
to/from RAM. Specifically, there will be several test cases that will
use different patterns to verify RAM. Each test case will first fill
a region of RAM with one pattern and then read the region back and
compare its contents with the pattern. The following patterns will be
used:
1) zero pattern (0x00000000)
2) negative pattern (0xffffffff)
3) checkerboard pattern (0x55555555, 0xaaaaaaaa)
4) bit-flip pattern ((1 << (offset % 32)), ~(1 << (offset % 32)))
5) address pattern (offset, ~offset)
Patterns #1, #2 will help to find unstable bits. Patterns #3, #4 will
be used to detect adherent bits, i.e. bits whose state may randomly
change if adjacent bits are modified. The last pattern will be used
to detect far-located errors, i.e. situations when writing to one
location modifies an area located far from it. Also, usage of the
last pattern will help to detect memory controller misconfigurations
when RAM represents a cyclically repeated portion of a smaller size.
Being run in normal mode, the test will verify only small 4Kb regions
of RAM around each 1Mb boundary. For example, for 64Mb RAM the
following areas will be verified: 0x00000000-0x00000800,
0x000ff800-0x00100800, 0x001ff800-0x00200800, ..., 0x03fff800-
0x04000000. If the test is run in power-fail mode, it will verify the
whole RAM.
The memory test will run in ROM before relocating U-Boot to RAM in
order to allow RAM modification without saving its contents.
2.2.2. Common tests
This section describes tests that are not based on any hardware
peculiarities and use common U-Boot interfaces only. These tests do
not need any modifications for porting them to another board/CPU.
2.2.2.1. I2C test
For verifying the I2C bus, a full I2C bus scanning will be performed
using the i2c_probe() routine. If a board defines
CFG_SYS_POST_I2C_ADDRS the I2C test will pass if all devices
listed in CFG_SYS_POST_I2C_ADDRS are found, and no additional
devices are detected. If CFG_SYS_POST_I2C_ADDRS is not defined
the test will pass if any I2C device is found.
The CFG_SYS_POST_I2C_IGNORES define can be used to list I2C
devices which may or may not be present when using
CFG_SYS_POST_I2C_ADDRS. The I2C POST test will pass regardless
if the devices in CFG_SYS_POST_I2C_IGNORES are found or not.
This is useful in cases when I2C devices are optional (eg on a
daughtercard that may or may not be present) or not critical
to board operation.
2.2.2.2. Watchdog timer test
To test the watchdog timer the scheme mentioned above (refer to
section "Hazardous tests") will be used. Namely, this test will be
marked with the POST_REBOOT bit flag. On the first iteration, the
test routine will make a 10-second delay. If the system does not
reboot during this delay, the watchdog timer is not operational and
the test fails. If the system reboots, on the second iteration the
POST_REBOOT bit will be set in the flag argument to the test routine.
The test routine will check this bit and report a success if it is
set.
2.2.2.3. RTC test
The RTC test will use the rtc_get()/rtc_set() routines. The following
features will be verified:
o) Time uniformity
This will be verified by reading RTC in polling within a short
period of time (5-10 seconds).
o) Passing month boundaries
This will be checked by setting RTC to a second before a month
boundary and reading it after its passing the boundary. The test
will be performed for both leap- and nonleap-years.
2.2.3. MPC8xx peripherals tests
This project will develop a set of tests verifying the peripheral
units of MPC8xx processors. Namely, the following controllers of the
MPC8xx communication processor module (CPM) will be tested:
o) Serial Management Controllers (SMC)
o) Serial Communication Controllers (SCC)
2.2.3.1. Ethernet tests (SCC)
The internal (local) loopback mode will be used to test SCC. To do
that the controllers will be configured accordingly and several
packets will be transmitted. These tests may be enhanced in future to
use external loopback for testing. That will need appropriate
reconfiguration of the physical interface chip.
The test routines for the SCC ethernet tests will be located in
arch/powerpc/cpu/mpc8xx/scc.c.
2.2.3.2. UART tests (SMC/SCC)
To perform these tests the internal (local) loopback mode will be
used. The SMC/SCC controllers will be configured to connect the
transmitter output to the receiver input. After that, several bytes
will be transmitted. These tests may be enhanced to make to perform
"external" loopback test using a loopback cable. In this case, the
test will be executed manually.
The test routine for the SMC/SCC UART tests will be located in
arch/powerpc/cpu/mpc8xx/serial.c.
2.2.3.3. USB test
TBD
2.2.3.4. SPI test
TBD
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