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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Date:	Wed, 16 Oct 2013 18:40:30 +0530
From:	Kishon Vijay Abraham I <kishon@...com>
To:	Roger Quadros <rogerq@...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

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.

Thanks
Kishon
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