Hi David,
On 4/28/20 1:58 AM, David Santamaría Rogado wrote:
This is related to the issues at least on some devices for panel
orientation quirks where added.
Thank you for looking into this.
My tests have been done over a Lenovo ideapad D330.
This devices like the other ones that need panel orientation quirks,
shows the initramfs with wrong stride and x and y swapped. By applying
the panel orientation quirks this gets solved but many parts of the
systems components needs to be patched. Hans has done a great job with
plymouth, mutter... but always appears a new problem derived as for
example vnc desktop sharing with this devices doesn't work and the
output is send messed up.
When I first started adding support for devices which have their
screen mounted 90 degrees rotated my first attempts where aimed
at solving this transparently in the kernel.
Unfortunately this is not possible. On most affected devices
the hardware does not support 90 degrees rotation for the
primary display layer; or if it does this requires the framebuffer
being in a hardware-specific tiled format rather then being a
linear framebuffer. Using these tiled formats requires userspace
to be aware of this, which rules out transparently handling this
in the kernel.
Other layers (cursor layer, video overlay layers) have similar
issues which require userspace to be aware of what is happening,
so unfortunately there is no other way to deal with this then
fixing involved userspace components.
I'm a bit surprised that you sat that vnc desktop sharing does
not work, I guess that also depends on how the desktop sharing
works. If it pokes directly at the framebuffer somehow, then yes
it will be messed up. But if it goes through the display server
then things might work. I guess that it is possible that the
code doing this cannot deal with Xrandr output rotation ...
The strange thing is that bootloaders like GRUB or rEFInd seems to be
able to handle this and they paint themselves right, despite when
booting Windows directly Windows paints itself right and booted with
GRUB or rEFInd the first second also paint itself wrong. Haven't
tested this too much but the interesting thing is in the next
paragraph.
My experience with bootloaders showing themselves the right way
up is mixed. It seems that the firmware is doing some hacks for
this on some devices, at least for the EFI text console.
Funnily enough (for some definition of fun) on at least one of
the devices where the firmware is playing tricks (Asus T100HA IIRC)
the position of the carret for text-editing is off by one, which
is very annoying when editing the kernel commandline and which
clearly shows that things are being emulated in software here.
I decided to get the UEFI GOP video modes and found that the D330 have
these ones:
Mode 0: 1200x1920
Mode 1: 640x480
Mode 2: 800x600
Mode 3: 1024x768
Mode 4: 1920x1200 (this is the default one started by the firmware)
Mode 5: 480x640
Mode 6: 600x800
Mode 7: 768x1024
So I thought that Linux is taking the first mode despite is not the
active one and that's why the display is messed up.
Nope, Linux does not touch the mode at all (nor does grub by default).
Doing a EFI/GOP modeset has the risk of triggering all sort of firmware
bugs. So we stick with what we get. This has interesting side effects
where on some systems you get a different mode when turning on the
machine and letting it boot, vs turning it on, pressing e.g. F12 to get
the boot menu and then boot Linux.
Playing a little I could modify the GOP video mode before booting with
the UEFI Shell by simple using the mode 150 101. This causes GOP video
mode 5 to be switched to video mode 0, the first one. Booting now
makes initramfs messages to be correctly rendered but in the wrong
orientation.
Right, the rendering on the side thing is expected. As said the hardware
cannot do 90 degrees rotation with a linear framebuffer and the GOP
provided efifb is a linear framebuffer. So without telling the kernel
to software rotate its text console the text will always be on its side.
What your little EFI shell hack is doing is working around what seems to
be a bug on these Lenovo devices gives us the wrong stride and dimensions
for the EFI framebuffer.
Note that this very much is a Lenovo bug, all the other devices
with 90 degree rotated screens let us render the text console
on its side just fine. They correctly tells us the real size
and stride of the screen (so its portrait dimensions since it
is a portrait screen).
Even though this is a Lenovo bug we should probably still try to
find a way to deal with this though, so that the efifb works
correctly on these devices...
A look at drivers/firmware/efi/libstub/gop.c seems to be what is
happening, the first available video mode is used despite it could not
be the active one in GOP and the active mode is not switched to the
discovered one by Linux. Both GRUB and rEFInd are able to respect the
video mode that GOP has active so it's possible to boot them landscape
and portrait while being correctly rendered.
I think the video mode should not be the first discovered one but the
active one, or at least, the highest resolution video mode that
respects the orientation.
Again, Linux does not use the GOP concept of video modes at all,
it simply takes the active mode as reported by the UEFI and uses
that to show messages during early boot.
Also note that fixing the efifb is of little value early during
boot the kernel will load the i915 driver so that we can have
hardware rendered 3D, support for multiple monitors, etc. and as
soon as that is loaded the efifb settings no longer matter.
The i915 driver does not care about the GOP settings at all;
and without a quirk it too will cause everything to be rendered
on its side.
Regards,
Hans
