[PATCH v4 5/5] usb: dwc3: rockchip: add devicetree bindings documentation

Heiko Stuebner heiko at sntech.de
Tue Jun 28 09:41:28 PDT 2016

Hi William,

Am Dienstag, 28. Juni 2016, 11:18:04 schrieb William Wu:
> >> So about the usb3 controller clk management, I think it should contain
> >> the following clk:
> >> 1.  aclk_usb3otg1
> >> 2.  aclk_usb3otg0
> >> 3.  aclk_usb3_grf
> > 
> > correct, aclk_usb3otgX would then be the busclk for each controller if
> > I'm not mistaken and the grf clock should also get enabled, like we
> > also plan on doing for the vio_grf clock in the display area.
> OK, so  aclk_usb3_grf should be marked as critical, right?

nope ... the consensus for the vio_grf clock was that the driver accessing 
it should control it. So for the usb3_grf clock this would be your dwc3-
based driver being responsible for the grf-clock.

> I found that most of the grf clocks haven't been marked as critical,
> apart from vio_grf. So may I keep the aclk_usb3_grf in usb3 dts, and
> remove it after clock manager adds it to critical clocks?

you should keep the usb3-grf clock in the dts all the time.

> >> 4.  aclk_usb3_noc
> >> For "aclk_usb3_noc", I discuss with our clk manager, the clk is always
> >> on before,
> >> but according to upstream maintainer's suggestion, we need to manage
> >> the
> >> noc clk by each module.
> > 
> > can you point me to this discussion? The bus-interconnect is a very
> > separate component, which we don't model so far and thus we have all
> > the noc clocks simply marked as critical.
> > 
> > As this clock doesn't belong to the actual usb controller block, but
> > said
> > separate component, handling it in the controller seems somehow wrong to
> > me.
> > 
> > So my (current) opinion would again be to mark the noc clock as critical
> > for the time being.
> Sorry, it seems that I get the new information about clk management too
> late.:-)
> There's no dedicated discussion about noc clk, but similar to grf clock,
> please refer to "https://patchwork.kernel.org/patch/9171467/" for add
> pclk_vio_grf to critical clock on the RK3399, and you have agreed on
> that mark vio grf clk as critical. So I agree with your opinion, thanks~

The difference as I see it is, that the GRF parts are _part_ of the usb3 
controller, while the interconnect really is a separate component, 
connecting the controller to the rest of the system.

|  USB3  |----[Interconnect]----[rest of the system]
| [+GRF] |	

So the controller binding + driver should handle all clocks it needs to 
operate. We currently don't model and handle the separate interconnect 
though, so that noc clock should be critical for the time being.


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