Re: [PATCH RFC v3 04/11] arm64: dts: qcom: msm8939: Add venus node

[Erikas Bitovtas <xerikasxx@gmail.com>]

On 4/28/26 10:10 AM, Bryan O'Donoghue wrote:
> On 27/04/2026 18:58, Erikas Bitovtas wrote:
>> +            video-decoder {
>> +                compatible = "venus-decoder";
>> +                clocks = <&gcc GCC_VENUS0_CORE0_VCODEC0_CLK>,
>> +                     <&gcc GCC_VENUS0_CORE1_VCODEC0_CLK>;
>> +                clock-names = "core0", "core1";
>> +                power-domains = <&gcc VENUS_CORE0_GDSC>,
>> +                        <&gcc VENUS_CORE1_GDSC>;
>> +                power-domain-names = "core0", "core1";
>> +            };
>> +
>> +            video-encoder {
>> +                compatible = "venus-encoder";
>> +                clocks = <&gcc GCC_VENUS0_CORE0_VCODEC0_CLK>,
>> +                     <&gcc GCC_VENUS0_CORE1_VCODEC0_CLK>;
>> +                clock-names = "core0", "core1";
>> +                power-domains = <&gcc VENUS_CORE0_GDSC>,
>> +                        <&gcc VENUS_CORE1_GDSC>;
>> +                power-domain-names = "core0", "core1";
>> +            };
> 
> So to be fair in this case you do have a reason to have an encoder and
> decoder compatible here _but_ it should be the case that one one of the
> sub-devices contains CORE0 related stuff and the other CORE1 related stuff.
> 
> Because in that case the sub-devices actually represent individual
> hardware settings.
> 
> So listing power-domains and clocks for both cores in each node like
> this militates against that.
> 
> The other thing is to double check of the encoder and decoder are inter-
> changable here i.e. can either core be encoder or decoder or is it fixed ?
> 
> I believe on older generations - perhaps not on 8939 it is not
> interchangable.
> 
I found this in LA.BR.1.2.9.1_rb1.5:
https://github.com/msm8916-mainline/linux-downstream/blob/b20608408caff817ec874f325127b07609fbaeb8/arch/arm/boot/dts/qcom/msm8939-common.dtsi#L1589
Only decoder bits are being set in bus configs. This suggests that the
cores are not interchangeable.
Then again, I never managed to get encoding working on MSM8939. Testing
it with
gst-launch-1.0 videotestsrc ! videoconvert ! v4l2vp8enc ! queue !
v4l2vp8dec ! xvimagesink
Fails with the following log: https://pastebin.com/nmZcLgPV
And in dmesg it reports a firmware error:
[  784.461031] qcom-venus 1d00000.video-codec: no valid instance(pkt
session_id:dead, pkt:21001)
[  784.461126] qcom-venus-decoder 1d00000.video-codec:video-decoder:
dec: event session error 0
[  784.461200] qcom-venus-encoder 1d00000.video-codec:video-encoder:
enc: event session error 0
[  784.468799] qcom-venus 1d00000.video-codec: SFR message from FW:
QC_IMAGE_VERSION_STRING=VIDEO.VE.1.8-00099, Err_Fatal -
Z:\b\venus\utils\src\vbuffer.c:1319:
[  785.791641] qcom-venus 1d00000.video-codec: System error has
occurred, recovery failed to init HFI
[  787.018339] qcom-venus 1d00000.video-codec: System error has
occurred, recovery failed to init HFI
[  787.097253] qcom-venus 1d00000.video-codec: system error has occurred
(recovered)
This happens regardless of whether I enable the cores for encoding too
or not. The same errors were happening on MSM8916 as well. So I can't
tell if these cores are interchangeable just by testing.