spi_flash: Make .read() callback optional

All SPI flash chip drivers currently in coreboot use the generic read
functions (spi_flash_cmd_read_fast()/_slow()) as their read callback.
The only use case for specialized read callbacks we have left is with
specialized flash controllers like Intel fast_spi (which sort of
impersonate the flash chip driver by implementing their own probe
function).

This patch unifies the behavior for all normal flash drivers by making
the read callback optional and letting them all fall back to a default
read implementation that handles normal fast/slow reading. Most of the
drivers used to install the respective callback after checking
CONFIG_SPI_FLASH_NO_FAST_READ, but some hardcoded either slow or fast
writes. I have found no indications for why this is and spot-checked
datasheets for affected vendors to make sure they all support both
commands, so I assume this is just some old inaccuracy rather than
important differences that need preserving. (Please yell if you
disagree.)

Also take the opportunity to refactor some of the common spi_flash.c
code a bit because I felt there are too many nested functions that don't
really do enough on their own, and centralizing stuff a bit should make
it easier to follow the code flow. (Some of this is in preparation for
the next patch.)

Change-Id: I2096a3ce619767b41b1b0c0c2b8e95b2bd90a419
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/33282
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-by: Furquan Shaikh <furquan@google.com>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
12 files changed
tree: 988e6860b7a4deac4fd424b8b0f294633acf12e2
  1. 3rdparty/
  2. configs/
  3. Documentation/
  4. payloads/
  5. src/
  6. util/
  7. .checkpatch.conf
  8. .clang-format
  9. .gitignore
  10. .gitmodules
  11. .gitreview
  12. COPYING
  13. gnat.adc
  14. MAINTAINERS
  15. Makefile
  16. Makefile.inc
  17. README.md
  18. toolchain.inc
README.md

coreboot README

coreboot is a Free Software project aimed at replacing the proprietary BIOS (firmware) found in most computers. coreboot performs a little bit of hardware initialization and then executes additional boot logic, called a payload.

With the separation of hardware initialization and later boot logic, coreboot can scale from specialized applications that run directly firmware, run operating systems in flash, load custom bootloaders, or implement firmware standards, like PC BIOS services or UEFI. This allows for systems to only include the features necessary in the target application, reducing the amount of code and flash space required.

coreboot was formerly known as LinuxBIOS.

Payloads

After the basic initialization of the hardware has been performed, any desired "payload" can be started by coreboot.

See https://www.coreboot.org/Payloads for a list of supported payloads.

Supported Hardware

coreboot supports a wide range of chipsets, devices, and mainboards.

For details please consult:

Build Requirements

  • make
  • gcc / g++ Because Linux distribution compilers tend to use lots of patches. coreboot does lots of "unusual" things in its build system, some of which break due to those patches, sometimes by gcc aborting, sometimes - and that's worse - by generating broken object code. Two options: use our toolchain (eg. make crosstools-i386) or enable the ANY_TOOLCHAIN Kconfig option if you're feeling lucky (no support in this case).
  • iasl (for targets with ACPI support)
  • pkg-config
  • libssl-dev (openssl)

Optional:

  • doxygen (for generating/viewing documentation)
  • gdb (for better debugging facilities on some targets)
  • ncurses (for make menuconfig and make nconfig)
  • flex and bison (for regenerating parsers)

Building coreboot

Please consult https://www.coreboot.org/Build_HOWTO for details.

Testing coreboot Without Modifying Your Hardware

If you want to test coreboot without any risks before you really decide to use it on your hardware, you can use the QEMU system emulator to run coreboot virtually in QEMU.

Please see https://www.coreboot.org/QEMU for details.

Website and Mailing List

Further details on the project, a FAQ, many HOWTOs, news, development guidelines and more can be found on the coreboot website:

https://www.coreboot.org

You can contact us directly on the coreboot mailing list:

https://www.coreboot.org/Mailinglist

Copyright and License

The copyright on coreboot is owned by quite a large number of individual developers and companies. Please check the individual source files for details.

coreboot is licensed under the terms of the GNU General Public License (GPL). Some files are licensed under the "GPL (version 2, or any later version)", and some files are licensed under the "GPL, version 2". For some parts, which were derived from other projects, other (GPL-compatible) licenses may apply. Please check the individual source files for details.

This makes the resulting coreboot images licensed under the GPL, version 2.