On 10/8/25 9:32 AM, Mukesh Ojha wrote:
> On Tue, Oct 07, 2025 at 02:55:04PM -0700, Manivannan Sadhasivam wrote:
>> On Tue, Oct 07, 2025 at 10:18:57PM +0530, Mukesh Ojha wrote:
>>> All the Lemans IOT variants boards are using Gunyah hypervisor which
>>> means that, so far, Linux-based OS could only boot in EL1 on those
>>> devices. However, it is possible for us to boot Linux at EL2 on these
>>> devices [1].
>>>
>>> When running under Gunyah, remote processor firmware IOMMU streams is
>>> controlled by the Gunyah however when Linux take ownership of it in EL2,
>>> It need to configure it properly to use remote processor.
>>>
>>> Add a EL2-specific DT overlay and apply it to Lemans IOT variant
>>> devices to create -el2.dtb for each of them alongside "normal" dtb.
>>>
>>> [1]
>>> https://docs.qualcomm.com/bundle/publicresource/topics/80-70020-4/boot-developer-touchpoints.html#uefi
>>>
>>> Signed-off-by: Mukesh Ojha <[email protected]>
>>> ---
[...]
>>> +&iris {
>>> + /* TODO: Add video-firmware iommus to start IRIS from EL2 */
>>
>> So the missing 'iommus' property is the only blocker to enable IRIS?
>
> Yes, but this would require some changes in the driver as well to create
> a platform device for the firmware and IOMMU domain, and to attach the
> firmware device to the domain.
"yes, but actually no"
>
> There was some discussion around this in v2[1], where I added support
> for video. However, the change involved hooking into the video-firmware
> property, which was used for Venus. There were concerns[2] about following
> the same approach for Iris, and due to that, we have dropped video
> support for now. However, an RFC has been posted from our side to
> handle such scenarios[3], as of now unclear about the direction for
> Iris.
>
>
> [1] https://lore.kernel.org/lkml/[email protected]/
>
> [2]
> https://lore.kernel.org/lkml/[email protected]/
>
> [3]
> https://lore.kernel.org/all/[email protected]/
>
> [4]
> https://lore.kernel.org/lkml/[email protected]/
Reword the comment to "/* More driver work is needed */" since there
is nothing more you can do at the moment and you most likely don't
want to block your series on resolving the above entanglement
Konrad
