Hi Ard,
On 12/23/22 16:42, Ard Biesheuvel wrote:
(cc Andy)
On Wed, 21 Dec 2022 at 11:54, Markuss Broks <markuss.broks@xxxxxxxxx> wrote:
Make the EFI earlycon driver be suitable for any linear framebuffers.
This should be helpful for early porting of boards with no other means of
output, like smartphones/tablets. There seems to be an issue with early_ioremap
function on ARM32, but I am unable to find the exact cause. It appears the mappings
returned by it are somehow incorrect, thus the driver is disabled on ARM.
The reason that this driver is disabled on ARM is because the struct
screen_info is not populated early enough, as it is retrieved from a
UEFI configuration table.
I believe I must be hitting some other bug then, since my driver should
not use `struct screen_info` when the arguments are specified manually
(e.g. in device-tree or in kernel command line options), and it still is
broken on ARM when they are. I got it to work on ARM when I moved the
early console initialization later into the kernel booting process, but
that mostly defeats the purpose of early console driver, I believe. I've
been thinking that it could be some stuff not getting initialized early
enough indeed, but I've got no clue what could it be.
early_ioremap() works fine on ARM as long as they mapping is torn down
before paging_init()
EFI early
console was disabled on IA64 previously because of missing early_memremap_prot,
and this is inherited to this driver.
This patch also changes
"This patch also changes ..." is usually a strong hint to self that
the patches need to be split up.
behavior on EFI systems, by selecting the mapping type
based on if the framebuffer region intersects with system RAM. If it does, it's
common sense that it should be in RAM as a whole, and so the system RAM mapping is
used. It was tested to be working on my PC (Intel Z490 platform), as well as several
ARM64 boards (Samsung Galaxy S9 (Exynos), iPad Air 2, Xiaomi Mi Pad 4, ...).
Markuss Broks (2):
drivers: serial: earlycon: Pass device-tree node
efi: earlycon: Add support for generic framebuffers and move to fbdev
subsystem
v1 -> v2:
- a new patch correcting serial/earlycon.c argument name to "offset" instead
of "node"
- move IA64 exclusion from EFI earlycon Kconfig to earlycon driver Kconfig
(IA64 has no early_memremap_prot)
- move driver from fbdev to console subsystem
- select EFI earlycon by default
- fetch stride manually from device-tree, as on some devices it seems stride
doesn't match the horizontal resolution * bpp.
- use saner format (e.g. 1920x1080x32 instead of 1920,1080,32).
Markuss Broks (3):
drivers: serial: earlycon: Pass device-tree node
efi: earlycon: move to video/console to prepare for changes
efi: earlycon: Add support for generic framebuffers
.../admin-guide/kernel-parameters.txt | 12 +-
MAINTAINERS | 5 +
drivers/firmware/efi/Kconfig | 7 +-
drivers/firmware/efi/Makefile | 1 -
drivers/firmware/efi/earlycon.c | 246 --------------
drivers/tty/serial/earlycon.c | 3 +
drivers/video/console/Kconfig | 11 +
drivers/video/console/Makefile | 1 +
drivers/video/console/earlycon.c | 305 ++++++++++++++++++
include/linux/serial_core.h | 1 +
10 files changed, 336 insertions(+), 256 deletions(-)
delete mode 100644 drivers/firmware/efi/earlycon.c
create mode 100644 drivers/video/console/earlycon.c
--
2.39.0
- Markuss
P.S. Just noticed I forgot to Ctrl^S the cover letter before saving...
The main change v3 does is separate the moving action and edit action
into two separate commits, I don't think there're more major changes.
With v4 I'd try to attach the proper version log.
