linux-kernel - Re: [PATCH 1/7] usb: dwc3: get "usb_phy" only if the platform indicates the presence of PHY

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Date:	Thu, 12 Sep 2013 16:56:34 +0530
From:	Vivek Gautam <gautamvivek1987@...il.com>
To:	Roger Quadros <rogerq@...com>
Cc:	Kishon Vijay Abraham I <kishon@...com>,
	Felipe Balbi <balbi@...com>,
	Benoit Cousson <bcousson@...libre.com>,
	Tony Lindgren <tony@...mide.com>,
	Rob Herring <rob.herring@...xeda.com>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Grant Likely <grant.likely@...aro.org>,
	Sylwester Nawrocki <s.nawrocki@...sung.com>,
	Kumar Gala <galak@...eaurora.org>,
	Stephen Warren <swarren@...dotorg.org>,
	Ian Campbell <ian.campbell@...rix.com>,
	Rob Landley <rob@...dley.net>, george.cherian@...com,
	Greg KH <gregkh@...uxfoundation.org>,
	linux-doc@...r.kernel.org, linux-omap@...r.kernel.org,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Linux USB Mailing List <linux-usb@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/7] usb: dwc3: get "usb_phy" only if the platform
 indicates the presence of PHY

Hi,


On Thu, Sep 12, 2013 at 4:34 PM, Roger Quadros <rogerq@...com> wrote:
> Hi,
>
> On 09/12/2013 01:47 PM, Vivek Gautam wrote:
>> On Thu, Sep 12, 2013 at 4:06 PM, Roger Quadros <rogerq@...com> wrote:
>>> Hi Kishon,
>>>
>>> On 09/02/2013 06:43 PM, Kishon Vijay Abraham I wrote:
>>>> There can be systems which does not have a external usb_phy, so get
>>>> usb_phy only if usb-phy property is added in the case of dt boot or if
>>>> platform_data indicates the presence of PHY. Also remove checking if
>>>> return value is -ENXIO since it's now changed to always enable usb_phy layer.
>>>>
>>>> Signed-off-by: Kishon Vijay Abraham I <kishon@...com>
>>>> ---
>>>>  drivers/usb/dwc3/Kconfig         |    1 +
>>>>  drivers/usb/dwc3/core.c          |   60 +++++++++++++++++---------------------
>>>>  drivers/usb/dwc3/platform_data.h |    1 +
>>>>  3 files changed, 28 insertions(+), 34 deletions(-)
>>>>
>>>> diff --git a/drivers/usb/dwc3/Kconfig b/drivers/usb/dwc3/Kconfig
>>>> index f969ea2..cfc16dd 100644
>>>> --- a/drivers/usb/dwc3/Kconfig
>>>> +++ b/drivers/usb/dwc3/Kconfig
>>>> @@ -2,6 +2,7 @@ config USB_DWC3
>>>>       tristate "DesignWare USB3 DRD Core Support"
>>>>       depends on (USB || USB_GADGET) && GENERIC_HARDIRQS && HAS_DMA
>>>>       depends on EXTCON
>>>> +     select USB_PHY
>>>>       select USB_XHCI_PLATFORM if USB_SUPPORT && USB_XHCI_HCD
>>>>       help
>>>>         Say Y or M here if your system has a Dual Role SuperSpeed
>>>> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
>>>> index 474162e..428c29e 100644
>>>> --- a/drivers/usb/dwc3/core.c
>>>> +++ b/drivers/usb/dwc3/core.c
>>>> @@ -387,16 +387,38 @@ static int dwc3_probe(struct platform_device *pdev)
>>>>       if (node) {
>>>>               dwc->maximum_speed = of_usb_get_maximum_speed(node);
>>>>
>>>> -             dwc->usb2_phy = devm_usb_get_phy_by_phandle(dev, "usb-phy", 0);
>>>> -             dwc->usb3_phy = devm_usb_get_phy_by_phandle(dev, "usb-phy", 1);
>>>> +             if (of_property_read_bool(node, "usb-phy")) {
>>>> +                     dwc->usb2_phy = devm_usb_get_phy_by_phandle(dev,
>>>> +                             "usb-phy", 0);
>>>> +                     if (IS_ERR(dwc->usb2_phy))
>>>> +                             return PTR_ERR(dwc->usb2_phy);
>>>> +                     dwc->usb3_phy = devm_usb_get_phy_by_phandle(dev,
>>>> +                             "usb-phy", 1);
>>>> +                     if (IS_ERR(dwc->usb3_phy))
>>>> +                             return PTR_ERR(dwc->usb3_phy);
>>>
>>> Some DWC3 instances use only usb2_phy. e.g. on DRA7 the 2nd dwc3 instance doesn't use usb3_phy.
>>> This needs to be a valid case and driver shouldn't error out.
>>
>> So, i think adding flexibility to DWC3 to have either
>> usb2-phy/usb3-phy or both of them seems to be valid point.
>> Any suggestions ?
>>
>
> For high speed operation we need only usb2_phy but for super speed we need both usb2_phy
> and usb3_phy.
>
> Why would a dwc3 controller use only usb3_phy? A USB3.0 interface has to be compatible with
> USB2.0 as well, no?

True and for that reason we need both UTMI+ interface as well as PIPE3
interface, right ?
But as also mentioned in the thread:
https://lkml.org/lkml/2013/9/12/181, on Samsung exynos5
architecturally same block is managing UTMI+ and PIPE3 interfaces,
which is handled by phy-samsung-usb3 driver and denoted by "usb3_phy:
usbphy@...00000" node in "arch/arm/boot/dts/exynos5250.dtsi".

So on exynos5250, DWC3 really needs just usb3-phy, which is compatible
for USB 2.0 as well.

>
> cheers,
> -roger
>



-- 
Best Regards
Vivek
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