Hi Neil,
On 2020-11-17 08:49, Neil Armstrong wrote:
Hi Marc,
On 16/11/2020 21:07, Marc Zyngier wrote:
Hi all,
Having recently moved over to a top-of-the-tree u-boot on one of my
VIM3L systems in order to benefit from unrelated improvements
(automatic PCIe detection, EFI...), I faced the issue that my kernel
would hang like this:
[ OK ] Finished Helper to synchronize boot up for ifupdown.
[ OK ] Started Rule-based Manager for Device Events and Files.
[ 7.114516] VDDCPU: supplied by regulator-dummy
[ OK ] Found device /dev/ttyAML0.
[ 7.146862] meson-drm ff900000.vpu: Queued 2 outputs on vpu
[ 7.169630] fb0: switching to meson-drm-fb from simple
[ 7.169944] Console: switching to colour dummy device 80x25
[ 7.179250] meson-drm ff900000.vpu: CVBS Output connector not
available
and that's it.
After some poking around, I figured out that it is in the
meson-dw-hdmi module that the CPU was hanging...
I'll be interested in having your kernel config, I never had such
report
since I enabled HDMI support in U-Boot a few years ago.
Yeah, I was pretty surprised too. I have a hunch that this is caused
by u-boot DT exposing an extra MMIO region (dubbed "hhi") that gets
picked up by the kernel driver. *Not* having the region in the DT
(as in the kernel's version of the same DT) makes the driver work
exactly once:
Decompiled u-boot DT:
hdmi-tx@0 {
compatible = "amlogic,meson-g12a-dw-hdmi";
reg = <0x00 0x00 0x00 0x10000 0x00 0x3c000 0x00 0x1000>;
[...]
reg-names = "hdmitx\0hhi";
Decompiled kernel DT:
hdmi-tx@0 {
compatible = "amlogic,meson-g12a-dw-hdmi";
reg = <0x00 0x00 0x00 0x10000>;
There seem to be some complex interactions between the HDMI driver
and the DRM driver, both using this MMIO region at any given time.
But I admit not having tried very hard to follow the DRM maze of
intricate callbacks. All I needed was this box to reliably boot with
the firmware-provided DT.
You can find a reasonably recent version of my config at [1].
M.
[1] http://www.loen.fr/tmp/Config.full-arm64
--
Jazz is not dead. It just smells funny...
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