linux-kernel - Re: [PATCH v6 3/5] usb: dwc3: add phyif_utmi

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Date:	Wed, 13 Jul 2016 11:39:16 +0800
From:	"William.wu" <William.wu@...k-chips.com>
To:	Rob Herring <robh@...nel.org>, Heiko Stuebner <heiko@...ech.de>
Cc:	gregkh@...uxfoundation.org, balbi@...nel.org,
	linux-rockchip@...ts.infradead.org, briannorris@...gle.com,
	dianders@...gle.com, kever.yang@...k-chips.com,
	huangtao@...k-chips.com, frank.wang@...k-chips.com,
	eddie.cai@...k-chips.com, John.Youn@...opsys.com,
	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
	sergei.shtylyov@...entembedded.com, mark.rutland@....com,
	devicetree@...r.kernel.org
Subject: Re: [PATCH v6 3/5] usb: dwc3: add phyif_utmi_quirk

Dear Rob,


On 2016/7/11 22:54, Rob Herring wrote:
> On Fri, Jul 08, 2016 at 02:33:09PM +0200, Heiko Stuebner wrote:
>> Hi William,
>>
>> Am Donnerstag, 7. Juli 2016, 10:54:24 schrieb William Wu:
>>> Add a quirk to configure the core to support the
>>> UTMI+ PHY with an 8- or 16-bit interface. UTMI+ PHY
>>> interface is hardware property, and it's platform
>>> dependent. Normall, the PHYIf can be configured
>>> during coreconsultant. But for some specific usb
>>> cores(e.g. rk3399 soc dwc3), the default PHYIf
>>> configuration value is fault, so we need to
>>> reconfigure it by software.
>>>
>>> And refer to the dwc3 databook, the GUSB2PHYCFG.USBTRDTIM
>>> must be set to the corresponding value according to
>>> the UTMI+ PHY interface.
>>>
>>> Signed-off-by: William Wu <william.wu@...k-chips.com>
>>> ---
>> [...]
>>> diff --git a/Documentation/devicetree/bindings/usb/dwc3.txt
>>> b/Documentation/devicetree/bindings/usb/dwc3.txt index 020b0e9..8d7317d
>>> 100644
>>> --- a/Documentation/devicetree/bindings/usb/dwc3.txt
>>> +++ b/Documentation/devicetree/bindings/usb/dwc3.txt
>>> @@ -42,6 +42,10 @@ Optional properties:
>>>    - snps,dis-u2-freeclk-exists-quirk: when set, clear the
>>> u2_freeclk_exists in GUSB2PHYCFG, specify that USB2 PHY doesn't provide
>>>   			a free-running PHY clock.
>>> + - snps,phyif-utmi-quirk: when set core will set phyif UTMI+ interface.
>>> + - snps,phyif-utmi: the value to configure the core to support a UTMI+
>>> PHY +			with an 8- or 16-bit interface. Value 0 select 8-bit
>>> +			interface, value 1 select 16-bit interface.
>> maybe
>> 	snps,phyif-utmi-width = <8> or <16>;
> Seems like this could be common. Any other bindings have something
> similar already? If not "utmi-width" is fine.

It seems that there's not any dwc3 binding similar to this.
So I prefer to use “utmi-width”. :-)

>
>> devicetree is about describing the hardware, not the things that get written
>> to registers :-) . The conversion from the described width to the register
>> value can easily be done in the driver.
>>
>>
>> Also I don't think you need two properties for this. If the snps,phyif-utmi
>> property is specified it indicates that you want to manually set the width
>> and if it is absent you want to use the IC default. All functions reading
>> property-values indicate if the property is missing.
> Agreed.
>
> Rob
>
>
>