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(bd_t *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 board_power_mode(void)
  
       This routine will return the mode the system is running in
       (POST_POWERON, POST_NORMAL or POST_SHUTDOWN).
  
    o) void board_poweroff(void)
  
       This routine will turn off the power supply of the board. It
       will be called on power-fail booting after running all POST
       tests.

    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)(bd_t *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 CONFIG_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 CONFIG_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 CONFIG_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(bd_t *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 transfered 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
  CONFIG_SYS_POST_I2C_ADDRS the I2C test will pass if all devices
  listed in CONFIG_SYS_POST_I2C_ADDRS are found, and no additional
  devices are detected.  If CONFIG_SYS_POST_I2C_ADDRS is not defined
  the test will pass if any I2C device is found.

  The CONFIG_SYS_POST_I2C_IGNORES define can be used to list I2C
  devices which may or may not be present when using
  CONFIG_SYS_POST_I2C_ADDRS.  The I2C POST test will pass regardless
  if the devices in CONFIG_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