linux-kernel - Re: [PATCH v2 1/7] usb: dwc3: get "usb_phy" only if the platform indicates the presence of PHY's

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Message-ID: <525E943E.3080706@ti.com>
Date:	Wed, 16 Oct 2013 16:27:26 +0300
From:	Roger Quadros <rogerq@...com>
To:	Kishon Vijay Abraham I <kishon@...com>
CC:	<balbi@...com>, <gregkh@...uxfoundation.org>,
	<rob.herring@...xeda.com>, <pawel.moll@....com>,
	<mark.rutland@....com>, <swarren@...dotorg.org>,
	<ijc+devicetree@...lion.org.uk>, <rob@...dley.net>,
	<bcousson@...libre.com>, <tony@...mide.com>,
	<linux@....linux.org.uk>, <grant.likely@...aro.org>,
	<s.nawrocki@...sung.com>, <galak@...eaurora.org>,
	<devicetree@...r.kernel.org>, <linux-doc@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <linux-omap@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>, <linux-usb@...r.kernel.org>
Subject: Re: [PATCH v2 1/7] usb: dwc3: get "usb_phy" only if the platform
 indicates the presence of PHY's

On 10/16/2013 04:10 PM, Kishon Vijay Abraham I wrote:
> Hi roger,
> 
> On Wednesday 16 October 2013 06:33 PM, Roger Quadros wrote:
>> Hi Kishon,
>>
>> On 10/15/2013 10:54 PM, Kishon Vijay Abraham I wrote:
>>> There can be systems which does not have a external usb_phy, so get
>>> usb_phy only if dt data indicates the presence of PHY 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>
>>> ---
>>> In usb_get_phy_by_phandle, index 0 always refers to usb2 phy and index 1 always
>>> refers to usb3 phy. Since we've lived so long with this, this patch will make
>>> an assumption that if only one entry is populated in *usb-phy* property, it will
>>> be usb2 phy and the next entry will be usb3 phy.
>>>
>>>  drivers/usb/dwc3/Kconfig         |    1 +
>>>  drivers/usb/dwc3/core.c          |   72 ++++++++++++++++++++------------------
>>>  drivers/usb/dwc3/platform_data.h |    2 ++
>>>  3 files changed, 41 insertions(+), 34 deletions(-)
>>>
>>> diff --git a/drivers/usb/dwc3/Kconfig b/drivers/usb/dwc3/Kconfig
>>> index 70fc430..8e385b4 100644
>>> --- a/drivers/usb/dwc3/Kconfig
>>> +++ b/drivers/usb/dwc3/Kconfig
>>> @@ -1,6 +1,7 @@
>>>  config USB_DWC3
>>>  	tristate "DesignWare USB3 DRD Core Support"
>>>  	depends on (USB || USB_GADGET) && HAS_DMA
>>> +	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..cb91d70 100644
>>> --- a/drivers/usb/dwc3/core.c
>>> +++ b/drivers/usb/dwc3/core.c
>>> @@ -354,6 +354,7 @@ static int dwc3_probe(struct platform_device *pdev)
>>>  	struct device_node	*node = dev->of_node;
>>>  	struct resource		*res;
>>>  	struct dwc3		*dwc;
>>> +	int			count;
>>>  
>>>  	int			ret = -ENOMEM;
>>>  
>>> @@ -387,16 +388,49 @@ 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);
>>> +		count = of_count_phandle_with_args(node, "usb-phy", NULL);
>>> +		switch (count) {
>>> +		case 2:
>>> +			dwc->usb3_phy = devm_usb_get_phy_by_phandle(dev,
>>> +				"usb-phy", 1);
>>> +			if (IS_ERR(dwc->usb3_phy)) {
>>> +				dev_err(dev, "usb3 phy not found\n");
>>> +				return PTR_ERR(dwc->usb3_phy);
>>> +			}
>>> +		case 1:
>>> +			dwc->usb2_phy = devm_usb_get_phy_by_phandle(dev,
>>> +				"usb-phy", 0);
>>> +			if (IS_ERR(dwc->usb2_phy)) {
>>> +				dev_err(dev, "usb2 phy not found\n");
>>> +				return PTR_ERR(dwc->usb2_phy);
>>> +			}
>>> +			break;
>>
>> In the Exynos case, there is only 1 phy and it is the USB3 phy. This code
>> will wrongly treat it as usb2_phy.
> 
> That was the case even before this patch no? Unfortunately the old USB PHY
> library doesn't have APIs to get PHYs in a better way. If we try modifying the
> USB PHY library, it'll be kind of duplicating what is already there in the
> Generic PHY library. I'd rather prefer Exynos guys to use the new framework.

OK. I agree with you.
Do you know if there are users of dwc3 other than exynos5250 and omap5?
If not, we should get rid of the old USB PHY altogether.

cheers,
-roger
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