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

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Message-ID: <874nclghu2.fsf@ashishki-desk.ger.corp.intel.com>
Date:	Wed, 26 Jun 2013 15:46:45 +0300
From:	Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To:	Felipe Balbi <balbi@...com>, 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>,
	Alan Stern <stern@...land.harvard.edu>, mgr@...gutronix.de
Subject: Re: [PATCH] usb: dwc3: core: continue probe even if usb3 phy is not available

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?

Regards,
--
Alex
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