Re: [PATCH v9 06/10] usb: dwc3: qcom: Add support to read IRQ's related to multiport

[Krishna Kurapati PSSNV]

On 7/21/2023 2:05 PM, Johan Hovold wrote:
> On Sun, Jul 16, 2023 at 12:31:05AM +0530, Krishna Kurapati PSSNV wrote:
> > On 7/14/2023 4:10 PM, Krishna Kurapati PSSNV wrote:
> > > On 7/14/2023 2:35 PM, Johan Hovold wrote:
>
> > > > I haven't had time to look at your latest replies yet, but as I already
> > > > said when reviewing v9, it seems you should be using a common helper for
> > > > non-mp and mp.
>
> > >    The gist of my mail was to see if I can defer qcom probe when dwc3
> > > probe fails/or doesn't happen on of_plat_pop (which is logical) so that
> > > we can move setup_irq to after dwc3_register_core so that we know
> > > whether we are MP capable or not. This would help us move all IRQ
> > > reading into one function.
>
> >    I see it is difficult to write a common helper. To do so, we need to
> > know whether the device is MP capable or not in advance. And since it is
> > not possible to know it before of_plat_pop is done, I see only few ways
> > to do it:
> >
> > 1. Based on qcom node compatible string, I can read whether the device
> > is MP capable or not and get IRQ's accordingly.
>
> See, it's not impossible. You can also determine whether you have a
> multiport controller from looking at the interrupt names which are
> indexed and distinct for MP.
>
> > 2. Read the port_info in advance but it needs me to go through some DT
> > props and try getting this info. Or read xhci regs like we are doing in
> > core (which is not good). Also since some Dt props can be missing, is it
> > difficult to get the MP capability info before of_plat_pop is done.
>
> That seem unnecessary currently, but long term we probably need to fix
> the design of this driver and defer some setup using callbacks that are
> called when the core driver probes. Perhaps now is the time to add such
> functionality.
>
> > 3. Remove IRQ handling completely. Just because the device has IRQ's
> > present, I don't see a point in adding them to bindings, and because we
> > added them to bindings, we are making a patch to read them (and since
> > this is a little challenging, the whole of multiport series is blocked
> > although I don't need wakeup support on these interrupts right away).
>
> Again, no. The devicetree binding should describe the hardware
> capabilities and that has nothing to do with whether you need this for
> you current project or not.
>
> > Can't we let the rest of the patches go through and let interrupt
> > handling for 2nd, 3rd and 4rth ports be taken care later ? I am asking
> > this because I want the rest of the patches which are in good shape now
> > (after fixing the nits mentioned) to get merged atleast. I will make
> > sure to add interrupt handling later in a different series once this is
> > merged once I send v10.
>
> As I've explained in earlier mails, I don't think that is acceptable as
> you'd be dumping your technical debt on the community which will be left
> to clean up your mess.
>
> > Or if there is a simpler way to do it, I would be happy to take any
> > suggestions and complete this missing part in this series itself.

Hi Johan,

 Thanks for these comments.

> Using the 'compatible' or 'interrupt-names' properties seems like the
> easiest way to determine whether you have an MP controller or not.

Yes, I can make a common helper to get IRQ's based on compatible. I also 
provided another implementation (which is more unambiguous and better I 
feel) on [1]. I will take one path forward based on your review of that 
patch as well.

Thanks a lot again for the reviews !

[1]: 
https://lore.kernel.org/all/f6f2456d-0067-6cd6-3282-8cae7c47a2d3@xxxxxxxxxxx/

Regards,
Krishna,