Re: [PATCH 2/4] dt-bindings: display: tegra: Add channel/syncpoint range properties

[Krzysztof Kozlowski <krzk@kernel.org>]

On 29/06/2026 06:02, Mikko Perttunen wrote:
> On Friday, June 26, 2026 7:26 PM Krzysztof Kozlowski wrote:
>> On Thu, Jun 25, 2026 at 06:26:43PM +0900, Mikko Perttunen wrote:
>>> On Thursday, June 25, 2026 5:36 PM Krzysztof Kozlowski wrote:
>>>> On Mon, Jun 22, 2026 at 05:22:51PM +0900, Mikko Perttunen wrote:
>>>>> Channels and syncpoints available may be limited when other system
>>>>
>>>> What are channels and syncpoints?
>>>
>>> Very host1x-specific hardware resources. Somewhat close to GPU channels
>>> and semaphores / fences if you're familiar with those.
>>>
>>>>
>>>>> components are using them. Add properties nvidia,channels and
>>>>> nvidia,syncpoints to limit the range of usable channels and/or
>>>>> syncpoints.
>>>>
>>>> Why isn't this deducible from the compatible?
>>>
>>> When Host1x is partitioned, the hypervisor (or other software entity
>>> with access to the non-vm host1x register regions) can configure which
>>> channels and syncpoints are available to each partition arbitrarily.
>>
>> So you will have different boards for the same SoC with different
>> values?
>>
> 
> Yes -- even the same board will have different values depending on the
> use case of the system. The hypervisor or bootloader has to update the
> properties according to the configuration it has programmed in the
> hardware.
> 
> I will update the commit message with clarification.
> 
>>>
>>> How that partitioning was done is not discoverable through hardware
>>> directly, so we need to pass that information through device tree.
>>>
>>>>
>>>> Also, nvidia,channels is too broad/generic. This is not ADC, right? And
>>>> channels is a common term in IIO. And in few other cases.
>>>
>>> It's not ADC. Yes, it's a common term in a lot of contexts. I can call
>>> it nvidia,host1x-channels if you prefer but that seems a bit redundant
>>> given the context.
>>
>> host1x is indeed poor, but maybe there is some way to be a bit more
>> descriptive? message-channels?
> 
> I would prefer to keep these as is -- anyone working with host1x will
> know what 'channels' and 'syncpoints' mean, and changing the name could
> cause confusion since the name would not match other code or
> documentation discussing these.
> 
> I can update the binding documentation with some more explanation about
> what these properties mean.

Property has only one meaning in DT schema, so basically you are now
fixing nvidia,channels to uint32-array for all possible use cases and
nvidia devices. Well, you have been warned.

Best regards,
Krzysztof