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

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Date:	Wed, 26 Jun 2013 13:16:47 +0300
From:	Felipe Balbi <balbi@...com>
To:	George Cherian <george.cherian@...com>
CC:	<linux-usb@...r.kernel.org>, <balbi@...com>,
	<linux-kernel@...r.kernel.org>, <gregkh@...uxfoundation.org>,
	<linux-omap@...r.kernel.org>
Subject: Re: [PATCH] usb: dwc3: core: continue probe even if usb3 phy is not
 available

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:

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 :-)

ps: don't forget to default to superspeed in case no property is passed.

-- 
balbi

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