Hi All,
A fellow laptop user has been looking into efi=novamap requirement. I
was sharing with him that I thought only firmware could solve this
problem and he has questioned me on that assertion and pointed me to
this commit:
https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/commit/?id=4e46…
It appears from my reading that efi=novamap is required because: It is
fiddly to make the kernel function SetVirtualAddressMap() work
correctly on AArch64. Without documentation for the laptops I care
about, it does not appear to be a valuable use of time to make
SetVirtualAddressMap() work. For now, efi=novamap is a good-enough
work-around.
Is that more a more accurate analysis on my part?
best regards,
Richard
--
Richard.Henwood(a)arm.com
Server Software Eco-System
Tel: +1 512 410 9612
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From: Rob Clark <robdclark(a)chromium.org>
Now that we can deal gracefully with bootloader (firmware) initialized
display on aarch64 laptops[1], the next step is to deal with the fact
that the same model of laptop can have one of multiple different panels.
(For the yoga c630 that I have, I know of at least two possible panels,
there might be a third.)
This is actually a scenario that comes up frequently in phones and
tablets as well, so it is useful to have an upstream solution for this.
The basic idea is to add a 'panel-id' property in dt chosen node, and
use that to pick the endpoint we look at when loading the panel driver,
e.g.
/ {
chosen {
panel-id = <0xc4>;
};
ivo_panel {
compatible = "ivo,m133nwf4-r0";
power-supply = <&vlcm_3v3>;
no-hpd;
ports {
port {
ivo_panel_in_edp: endpoint {
remote-endpoint = <&sn65dsi86_out_ivo>;
};
};
};
};
boe_panel {
compatible = "boe,nv133fhm-n61";
power-supply = <&vlcm_3v3>;
no-hpd;
ports {
port {
boe_panel_in_edp: endpoint {
remote-endpoint = <&sn65dsi86_out_boe>;
};
};
};
};
sn65dsi86: bridge@2c {
compatible = "ti,sn65dsi86";
...
ports {
#address-cells = <1>;
#size-cells = <0>;
...
port@1 {
#address-cells = <1>;
#size-cells = <0>;
reg = <1>;
endpoint@c4 {
reg = <0xc4>;
remote-endpoint = <&boe_panel_in_edp>;
};
endpoint@c5 {
reg = <0xc5>;
remote-endpoint = <&ivo_panel_in_edp>;
};
};
};
}
};
Note that the panel-id is potentially a sparse-int. The values I've
seen so far on aarch64 laptops are:
* 0xc2
* 0xc3
* 0xc4
* 0xc5
* 0x8011
* 0x8012
* 0x8055
* 0x8056
At least on snapdragon aarch64 laptops, they can be any u32 value.
However, on these laptops, the bootloader/firmware is not populating the
chosen node, but instead providing an "UEFIDisplayInfo" variable, which
contains the panel id. Unfortunately EFI variables are only available
before ExitBootServices, so the second patch checks for this variable
before EBS and populates the /chosen/panel-id variable.
[1] https://patchwork.freedesktop.org/series/63001/
Rob Clark (4):
dt-bindings: chosen: document panel-id binding
efi/libstub: detect panel-id
drm: add helper to lookup panel-id
drm/bridge: ti-sn65dsi86: use helper to lookup panel-id
Documentation/devicetree/bindings/chosen.txt | 69 ++++++++++++++++++++
drivers/firmware/efi/libstub/arm-stub.c | 49 ++++++++++++++
drivers/firmware/efi/libstub/efistub.h | 2 +
drivers/firmware/efi/libstub/fdt.c | 9 +++
drivers/gpu/drm/bridge/ti-sn65dsi86.c | 5 +-
drivers/gpu/drm/drm_of.c | 21 ++++++
include/drm/drm_of.h | 7 ++
7 files changed, 160 insertions(+), 2 deletions(-)
--
2.20.1
I'm curious, how have folks been adding the devicetree command to the
grub menu entry? So far I've been manually editing the grub.cfg since
that worked well with my development flow, but now things have changed
a bit for me, and I'm looking for a way that it would be appended
automatically when the config is autogenerated when installing a new
kernel.
-Jeff
