[PATCH v3 10/14] mach-snapdragon: fixup USB nodes

[Sumit Garg]

On Tue, 19 Mar 2024 at 20:15, Caleb Connolly <caleb.connolly at linaro.org> wrote:
>
> Hi Sumit,
>
> On 19/03/2024 13:49, Sumit Garg wrote:
> > Hi Caleb,
> >
> > On Tue, 19 Mar 2024 at 17:52, Caleb Connolly <caleb.connolly at linaro.org> wrote:
> >>
> >> We don't support USB super-speed in U-Boot yet, we lack the SS PHY
> >> drivers, however from my testing even with a PHY driver there seem to be
> >> other issues when talking to super-speed peripherals.
> >>
> >> In pursuit of maintaining upstream DT compatibility,
> >
> > I can understand the reasoning behind this but since we enable these
> > fixups for every Qcom platform it may turn out to be counter
> > productive. There can be embedded use-cases where bootup times have
> > stringent requirements. Also, depending upon CPU speed/freq the add-on
> > times due to these can be significant.
>
> I have measured this on a few different boards:
>
> On DB410c, the slowest board we currently support
> * of_live_build took 7228us
> * Fixing up USB nodes took 131us
> * Fixing up power domains took 88us
>
> On RB1 (the slowest new platform with a QCM2290 SoC)
> * of_live_build took 2078us
> * Fixing up USB nodes took 39us
> * Fixing up power domains took 27us
>
> The time taken initially to build the livetree is likely made back as it
> is much much faster to query than the flat tree (as you can see, walking
> every single node takes <100us on db410c). I took some rough
> measurements of the boot-to-console time on sdm845 (see the "enable
> livetree" patch) and basically concluded that the delta between live and
> flat trees is within the margin of error.
>
> If a specific board for whatever reason wants to avoid using OF_LIVE
> then I'm fine with that, db410c isn't using it for example.

Okay that's fair. Let's try this approach and see if it pans out well.

-Sumit