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

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Message-ID: <20130626121210.GA12640@arwen.pp.htv.fi>
Date:	Wed, 26 Jun 2013 15:12:11 +0300
From:	Felipe Balbi <balbi@...com>
To:	George Cherian <george.cherian@...com>
CC:	<balbi@...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>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.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 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 ?

-- 
balbi

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