linux-kernel - Re: [PATCH] usb: gadget: udc: atmel: Also get regmap for at91sam9x5-pmc

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Message-ID: <20160613092636.GA3240@piout.net>
Date:	Mon, 13 Jun 2016 11:26:36 +0200
From:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
To:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
Cc:	Felipe Balbi <balbi@...nel.org>,
	Nicolas Ferre <nicolas.ferre@...el.com>,
	Boris Brezillon <boris.brezillon@...e-electrons.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-arm-kernel@...ts.infradead.org, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: gadget: udc: atmel: Also get regmap for
 at91sam9x5-pmc

On 13/06/2016 at 10:56:08 +0200, Uwe Kleine-König wrote :
> Hello,
> 
> On Mon, Jun 13, 2016 at 10:47:30AM +0200, Alexandre Belloni wrote:
> > The "atmel,at91sam9g45-udc" compatible UDC is also used on at91sam9x5 so it
> > is also necessary to try to get the syscon for at91sam9x5-pmc.
> > 
> > Fixes: 4747639f01c9 ("usb: gadget: atmel: access the PMC using regmap")
> > Reported-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
> 
> I played with the AT91 during my non-work time, so please use
> uwe@...ine-koenig.org as my email address.
> 
> > Signed-off-by: Alexandre Belloni <alexandre.belloni@...e-electrons.com>
> > ---
> >  drivers/usb/gadget/udc/atmel_usba_udc.c | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/drivers/usb/gadget/udc/atmel_usba_udc.c b/drivers/usb/gadget/udc/atmel_usba_udc.c
> > index 18569de06b04..bb1f6c8f0f01 100644
> > --- a/drivers/usb/gadget/udc/atmel_usba_udc.c
> > +++ b/drivers/usb/gadget/udc/atmel_usba_udc.c
> > @@ -1920,6 +1920,8 @@ static struct usba_ep * atmel_udc_of_init(struct platform_device *pdev,
> >  
> >  	udc->errata = match->data;
> >  	udc->pmc = syscon_regmap_lookup_by_compatible("atmel,at91sam9g45-pmc");
> > +	if (IS_ERR(udc->pmc))
> > +		udc->pmc = syscon_regmap_lookup_by_compatible("atmel,at91sam9x5-pmc");
> >  	if (udc->errata && IS_ERR(udc->pmc))
> >  		return ERR_CAST(udc->pmc);
> 
> I didn't retest but I'm sure this makes usb gadget work on my AT91.
> Still I'm unsure if the patch is correct. Can
> 
> 	syscon_regmap_lookup_by_compatible("atmel,at91sam9g45-pmc")
> 
> return -EPROBE_DEFER? Are there other error codes that should be fatal
> enough to not try to look for a sam9x5-pmc?
> 

Well, if finding the PMC fails, you are probably not far enough in the
boot process to care about USB :)

Also, looking up the syscon will never return -EPROBE_DEFER because it
will create the regmap on first lookup, it doesn't matter where it is
coming from.

> Nearly orthogonal to the issue: An error message on failure would be
> nice. When I saw usb gadget broken I first had to add messages to this
> driver to see where it failed.
> 

Good point, this can probably go in a separate, less urgent patch.

-- 
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com