Repurpose the existing EFI earlyprintk code to implement support for
'earlycon=efi' for arm64 systems, allowing the graphical console
to be used instead of the serial port for early debug output.
Changes since v1:
- Rename earlycon= argument to 'efifb' to emphasize that this is specific
to the EFI framebuffer.
- Replace earlyprintk=efi entirely, rather than keep it alongside earlycon.
Since earlycon is typically enabled (along with the infrastructure), and
earlyprintk isn't, this does not result in a lot more code to be included,
but does make it more likely that a given [distro] kernel has support for
this enabled out of the box.
- Switch to write-combine mappings by default. This is the default for efifb,
and is actually required on arm64, since device attributes do not tolerate
unaligned accesses or other operations (such as DC ZVA) that rely on memory
semantics. This requires ARCH_USE_MEMREMAP_PROT to be wired up, which is
why a new patch #1 has been added.
- Since adding the 'ram' parameter for framebuffers in shared memory on cache
coherent devices is trivial after the switch to WC mappings, fold the change
into the main patch.
Cc: corbet@xxxxxxx
Cc: leif.lindholm@xxxxxxxxxx
Cc: graeme.gregory@xxxxxxxxxx
Cc: mingo@xxxxxxxxxx
Cc: tglx@xxxxxxxxxxxxx
Cc: linux-doc@xxxxxxxxxxxxxxx
Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
Cc: agraf@xxxxxxx
Cc: pjones@xxxxxxxxxx
Ard Biesheuvel (2):
x86: make ARCH_USE_MEMREMAP_PROT a generic Kconfig symbol
efi: x86: convert x86 EFI earlyprintk into generic earlycon
implementation
Documentation/admin-guide/kernel-parameters.txt | 8 +-
arch/Kconfig | 3 +
arch/x86/Kconfig | 5 +-
arch/x86/Kconfig.debug | 10 -
arch/x86/include/asm/efi.h | 1 -
arch/x86/kernel/early_printk.c | 4 -
arch/x86/platform/efi/Makefile | 1 -
arch/x86/platform/efi/early_printk.c | 240 --------------------
drivers/firmware/efi/Kconfig | 6 +
drivers/firmware/efi/Makefile | 1 +
drivers/firmware/efi/earlycon.c | 208 +++++++++++++++++
11 files changed, 226 insertions(+), 261 deletions(-)
delete mode 100644 arch/x86/platform/efi/early_printk.c
create mode 100644 drivers/firmware/efi/earlycon.c
--
2.20.1
