From: Marc Zyngier <maz@kernel.org>
To: Neil Armstrong <narmstrong@baylibre.com>
Cc: Martin Blumenstingl <martin.blumenstingl@googlemail.com>,
Kevin Hilman <khilman@baylibre.com>,
linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
linux-amlogic@lists.infradead.org, kernel-team@android.com,
linux-arm-kernel@lists.infradead.org,
Jerome Brunet <jbrunet@baylibre.com>
Subject: Re: [PATCH 0/4] drm/meson: Module removal fixes
Date: Tue, 17 Nov 2020 09:19:48 +0000 [thread overview]
Message-ID: <09de6683eea499cfd83ab0c67e0cdca2@kernel.org> (raw)
In-Reply-To: <0b429c41-421a-2ae0-66a0-a142c56acadd@baylibre.com>
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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next prev parent reply other threads:[~2020-11-17 9:19 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-16 20:07 [PATCH 0/4] drm/meson: Module removal fixes Marc Zyngier
2020-11-16 20:07 ` [PATCH 1/4] drm/meson: Free RDMA resources after tearing down DRM Marc Zyngier
2020-11-17 8:51 ` Neil Armstrong
2020-11-16 20:07 ` [PATCH 2/4] drm/meson: Unbind all connectors on module removal Marc Zyngier
2020-11-17 8:53 ` Neil Armstrong
2020-11-16 20:07 ` [PATCH 3/4] drm/meson: dw-hdmi: Register a callback to disable the regulator Marc Zyngier
2020-11-17 8:55 ` Neil Armstrong
2020-11-16 20:07 ` [PATCH 4/4] drm/meson: dw-hdmi: Ensure that clocks are enabled before touching the TOP registers Marc Zyngier
2020-11-17 8:56 ` Neil Armstrong
2020-11-17 8:49 ` [PATCH 0/4] drm/meson: Module removal fixes Neil Armstrong
2020-11-17 9:19 ` Marc Zyngier [this message]
2020-11-17 9:46 ` Neil Armstrong
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