Re: [PATCH v3 6/7] USB: ohci-at91: add usb_clk for transition tocommon clk framework

[boris brezillon]

Hello Alan,

On 16/07/2013 18:48, Alan Stern wrote:
> On Tue, 16 Jul 2013, Boris BREZILLON wrote:
>
> > The AT91 PMC (Power Management Controller) provides an USB clock used by
> > USB Full Speed host (ohci) and USB Full Speed device (udc).
> > The usb drivers (ohci and udc) must configure this clock to 48Mhz.
> > This configuration was formely done in mach-at91/clock.c, but this
> > implementation will be removed when moving to common clk framework.
> >
> > This patch add support for usb clock retrieval and configuration, and is
> > backward compatible with the current at91 clk implementation (if usb clk
> > is not found, it does not configure/enable the usb clk).
> But it does print a warning in the system log, right?
Yes it does.
> > @@ -144,6 +150,11 @@ static int usb_hcd_at91_probe(const struct hc_driver *driver,
> >   		goto err2;
> >   	}
> >   
> > +	uclk = clk_get(&pdev->dev, "usb_clk");
> > +	if (IS_ERR(uclk)) {
> > +		uclk = NULL;
> > +		dev_warn(&pdev->dev, "failed to get usb_clk\n");
> > +	}
> Is this really what you want for backward compatibility?
Here are some proposition to remove the warning message:

1) replace it with a dev_info and change the message:
    dev_info(&pdev->dev, "failed to get usb_clk (most likely using old 
at91 clk implementation)\n");
2) drop the log and silently ignore the missing clk (I'm not a big fan 
of this solution
    as it may lead to some errors if we're using new clk implem and the 
clock is really missing)
3) rework the current clk_set_rate function to accept clk_set_rate on 
usb clk and add clk_lookup entries
    for the usb clk (I'm not a big fan of this solution neither as this 
modifications will only be used for a short time
    until the transition to common clk framework is completed).
> Alan Stern

Thanks for your review.

Best Regards,

Boris
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