Re: [PATCH 1/3] usb: misc: generic_onboard_hub: add generic onboard USB HUB driver

[Peter Chen <peter.chen-KZfg59tc24xl57MIdRCFDg@public.gmane.org>]

On Wed, Dec 09, 2015 at 10:10:51AM +0100, Arnd Bergmann wrote:
> On Wednesday 09 December 2015 09:57:40 Lucas Stach wrote:
> > Am Mittwoch, den 09.12.2015, 16:50 +0800 schrieb Peter Chen:
> > > On Tue, Dec 08, 2015 at 08:36:00AM -0700, Mathieu Poirier wrote:
> > > > On 7 December 2015 at 18:37, Peter Chen <peter.chen-KZfg59tc24xl57MIdRCFDg@public.gmane.org> wrote:
> > > > > +
> > > > > +       if (dev->of_node) {
> > > > > +               struct device_node *node = dev->of_node;
> > > > > +
> > > > > +               hub_data->clk = devm_clk_get(dev, "external_clk");
> > > > > +               if (IS_ERR(hub_data->clk)) {
> > > > > +                       dev_dbg(dev, "Can't get external clock: %ld\n",
> > > > > +                                       PTR_ERR(hub_data->clk));
> > > > > +               }
> > > > 
> > > > Is the intended behaviour to keep going here event when there is an
> > > > error?  Can the "hub_data" really work without a clock?
> > > 
> > > Yes, some HUB may work with fixed 24M OSC at the board, but they need to
> > > reset through external IO, so the clock is not need at this case, but
> > > reset pin is mandatory.
> > > 
> > If the hub always requires a clock it must not be optional. If you have
> > a fixed 24MHz clock on board add this to the DT as a fixed-clock and use
> > it as an input to the hub.
> 
> I think it's fine to make the clock optional in the sense that you only
> need to list non-fixed clocks that have to be enabled and or controlled.
> 
> Which reminds me, should the driver call clk_set_rate()? It currently
> doesn't, but other machines might need that.
> 

Yes, you are right, I will add it at v2.

-- 

Best Regards,
Peter Chen
--
To unsubscribe from this list: send the line "unsubscribe linux-usb" in
the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html