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

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Date:   Tue, 6 Sep 2022 18:54:26 +0200
From:   Ard Biesheuvel <ardb@...nel.org>
To:     Markuss Broks <markuss.broks@...il.com>
Cc:     linux-kernel@...r.kernel.org,
        ~postmarketos/upstreaming@...ts.sr.ht, phone-devel@...r.kernel.org,
        Jonathan Corbet <corbet@....net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Helge Deller <deller@....de>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Borislav Petkov <bp@...e.de>,
        Kees Cook <keescook@...omium.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        Damien Le Moal <damien.lemoal@...nsource.wdc.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Michal Suchanek <msuchanek@...e.de>,
        Javier Martinez Canillas <javierm@...hat.com>,
        Arnd Bergmann <arnd@...db.de>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Wei Ming Chen <jj251510319013@...il.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Tony Lindgren <tony@...mide.com>, linux-doc@...r.kernel.org,
        linux-efi@...r.kernel.org, linux-serial@...r.kernel.org,
        linux-fbdev@...r.kernel.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH v2 0/3] Add generic framebuffer support to EFI earlycon driver

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