linux-kernel - Re: [PATCH] usb: dwc3: core: continue probe even if usb3 phy is not available

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Date:	Thu, 27 Jun 2013 08:14:16 +0200
From:	Michael Grzeschik <mgr@...gutronix.de>
To:	Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc:	Felipe Balbi <balbi@...com>,
	George Cherian <george.cherian@...com>,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	gregkh@...uxfoundation.org, linux-omap@...r.kernel.org,
	Kishon Vijay Abraham I <kishon@...com>,
	Alan Stern <stern@...land.harvard.edu>
Subject: Re: [PATCH] usb: dwc3: core: continue probe even if usb3 phy is
 not available

On Wed, Jun 26, 2013 at 03:46:45PM +0300, Alexander Shishkin wrote:
> Felipe Balbi <balbi@...com> writes:
> 
> > On Wed, Jun 26, 2013 at 05:37:19PM +0530, George Cherian wrote:
> >> On 6/26/2013 3:46 PM, Felipe Balbi wrote:
> >> >Hi,
> >> >
> >> >On Wed, Jun 26, 2013 at 02:59:14PM +0530, George Cherian wrote:
> >> >>There can be configurations in which DWC3 is hoooked up only to USB2 PHY.
> >> >>In such cases we should not return -EPROBE_DEFER, rather continue probe
> >> >>even if there is no USB3 PHY.
> >> >>
> >> >>Signed-off-by: George Cherian <george.cherian@...com>
> >> >>---
> >> >>  drivers/usb/dwc3/core.c | 31 ++++++++++++++++++++++++-------
> >> >>  1 file changed, 24 insertions(+), 7 deletions(-)
> >> >>
> >> >>diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> >> >>index c35d49d..d5e6f3e 100644
> >> >>--- a/drivers/usb/dwc3/core.c
> >> >>+++ b/drivers/usb/dwc3/core.c
> >> >>@@ -100,7 +100,9 @@ static void dwc3_core_soft_reset(struct dwc3 *dwc)
> >> >>  	dwc3_writel(dwc->regs, DWC3_GUSB2PHYCFG(0), reg);
> >> >>  	usb_phy_init(dwc->usb2_phy);
> >> >>-	usb_phy_init(dwc->usb3_phy);
> >> >>+
> >> >>+	if (dwc->usb3_phy)
> >> >>+		usb_phy_init(dwc->usb3_phy);
> >> >I would feel more comfortable if you would move our maximum_speed module
> >> >parameter to DT with a property such as:
> >> >
> >> >snps,maximum_speed = "highspeed";
> >> >
> >> >then on driver you could:
> >> okay
> >> >ret = of_property_read_string(np, "snps,maximum_speed", &maximum_speed);
> >> >if (ret < 0)
> >> >	bailout();
> >> >
> >> >if (strncmp(maximum_speed, "superspeed", 10) == 0) {
> >> >	/* grab USB3 PHY, return EPROBE_DEFER if not found */
> >> >	grab_usb3_phy();
> >> >}
> >> >
> >> >if ((strncmp(maximum_speed, "highspeed", 9) == 0) ||
> >> >	(strncmp(maximum_speed, "fullspeed", 9) == 0) ||
> >> >	(strncmp(maximum_speed, "lowspeed", 8) == 0)) {
> >> >	/* grab USB2 PHY, return EPROBE_DEFER if not found */
> >> >	grab_usb2_phy();
> >> >}
> >> >
> >> >this way, we depend solely on setting maximum_speed to highspeed for
> >> >AM437x :-)
> >> In dra7xx one instance is superspeed and one instance highspeed.
> >
> > right, but in DT you will define both instances and each instance will
> > have a seaparate snps,maximum_speed attribute :-)
> >
> > I'm now considering if we should make maximum_speed a generic attribute,
> > Kishon ? Alex ? Alan ?
> >
> > anyone else needs such thing ?
> 
> We have a force-full-speed attibute for chipidea on the way. This
> maximum_speed looks like a more generic alternative. Michael, what say
> you?

The maximum_speed attribute sounds more reasonable. I will change my
patch to it.

Regards,
Michael

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