Re: [PATCH v2 0/3] Add generic framebuffer support to EFI earlycon driver

Ard Biesheuvel
2022-09-06T17:07:29Z

On Sat, 6 Aug 2022 at 18:34, Markuss Broks <markuss.broks@gmail.com> 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. 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 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

Wasn't EFI earlycon already enabled 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).
>
> .../admin-guide/kernel-parameters.txt | 12 +-
> MAINTAINERS | 5 +
> drivers/firmware/efi/Kconfig | 6 +-
> drivers/firmware/efi/Makefile | 1 -
> drivers/firmware/efi/earlycon.c | 246 --------------
> drivers/tty/serial/earlycon.c | 3 +
> drivers/video/fbdev/Kconfig | 11 +
> drivers/video/fbdev/Makefile | 1 +
> drivers/video/fbdev/earlycon.c | 301 ++++++++++++++++++
> include/linux/serial_core.h | 1 +
> 10 files changed, 331 insertions(+), 256 deletions(-)
> delete mode 100644 drivers/firmware/efi/earlycon.c
> create mode 100644 drivers/video/fbdev/earlycon.c
>
> --
> 2.37.0
>