Re: [PATCH 2/2] phy: qcom-mipi-csi2: Add a CSI2 MIPI D-PHY driver

[Bryan O'Donoghue <bryan.odonoghue@linaro.org>]

On 22/07/2025 10:59, Neil Armstrong wrote:
> On 22/07/2025 11:08, Bryan O'Donoghue wrote:
>> On 22/07/2025 09:32, Neil Armstrong wrote:
>>> The whole key point here is the combo mode, as I understood the combo 
>>> mode feature
>>> makes the PHY lanes available as 2 separate streams, like if you got 
>>> 2 "controllers"
>>> attached to the same PHY. So in fact, the PHY should have a single 
>>> node, but 2 PHY
>>> interfaces in combo mode.
>>>
>>> This makes all this controller/phy model very complex to handle and 
>>> add a lot of
>>> logic in the camss side. Moving the "csiphy" as an independent media 
>>> device that
>>> can declare up to 2 endpoints in combo mode makes things much 
>>> simpler, and allows
>>> us to attach each "csiphy" stream to any "controller" side of camss.
>>
>> I think there should be a generic extension to PHY/linux-media to 
>> support that instead of something Qualcomm specific.
> 
> Can you point out what's missing ? AFAIK it's more a matter of proper 
> representation of all
> the CAMSS components with a proper ports/endpoint graph design that 
> adding new kernel APIs.

Perhaps I'm not understanding the pushback.

Vlad's design puts the CSIPHY nodes under CAMSS and doesn't use the 
upstream PHY API, which if I've understood right is done to facilitate 
multiple sensors on the same CSIPHY.

If the kernel APIs or standard representations of CSIPHYs in the 
upstream kernel are insufficent to facilitate this model, then I think 
that change should be done separately so that all of the existing 
upstream stuff can benefit.

CAMSS should have a standard PHY interface. That's what this series 
provides.

If multiple sensors on the CSIPHY can't fit into that standard model, 
then we need a series to rectify.

I've given an example of how two sensors could be routed to one CSIPHY 
in DT. Another possibility is virtual channels.

I don't know if your sensors support VCs, have you explored that ?

If the message is "we need a custom PHY interface in CAMSS for multiple 
sensors" then I think in fact what that points to additional work that 
needs to be done in CAMSS and perhaps in the kernel linux-media and PHY 
layer to facilitate.

Like I say I'm happy to help you guys do that, ship me some hardware.

---
bod