linux-kernel - Re: [PATCH v3 2/3] USB3/DWC3: Add property "snps, incr-burst-type-adjustment" for INCR burst type

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Message-ID: <CAL_JsqJuifiSQAt-6FgtYYSukAnjzOLuTGEsO-Spn5LxkU-iwQ@mail.gmail.com>
Date:   Tue, 3 Jan 2017 15:23:46 -0600
From:   Rob Herring <robh@...nel.org>
To:     Jerry Huang <jerry.huang@....com>
Cc:     "balbi@...nel.org" <balbi@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "catalin.marinas@....com" <catalin.marinas@....com>,
        "will.deacon@....com" <will.deacon@....com>,
        "linux@...linux.org.uk" <linux@...linux.org.uk>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v3 2/3] USB3/DWC3: Add property "snps, incr-burst-type-adjustment"
 for INCR burst type

On Thu, Dec 22, 2016 at 8:52 PM, Jerry Huang <jerry.huang@....com> wrote:
> Hi, Rob,
>> -----Original Message-----
>> From: Rob Herring [mailto:robh@...nel.org]
>> Sent: Friday, December 23, 2016 2:45 AM
>> To: Jerry Huang <jerry.huang@....com>
>> Cc: balbi@...nel.org; mark.rutland@....com; catalin.marinas@....com;
>> will.deacon@....com; linux@...linux.org.uk; devicetree@...r.kernel.org;
>> linux-usb@...r.kernel.org; linux-kernel@...r.kernel.org; linux-arm-
>> kernel@...ts.infradead.org
>> Subject: Re: [PATCH v3 2/3] USB3/DWC3: Add property "snps, incr-burst-
>> type-adjustment" for INCR burst type
>>
>> On Mon, Dec 19, 2016 at 05:25:53PM +0800, Changming Huang wrote:
>> > New property "snps,incr-burst-type-adjustment = <x>, <y>" for USB3.0
>> DWC3.
>> > Field "x": 1/0 - undefined length INCR burst type enable or not; Field
>> > "y": INCR4/INCR8/INCR16/INCR32/INCR64/INCR128/INCR256 burst type.
>> >
>> > While enabling undefined length INCR burst type and INCR16 burst type,
>> > get better write performance on NXP Layerscape platform:
>> > around 3% improvement (from 364MB/s to 375MB/s).
>> >
>> > Signed-off-by: Changming Huang <jerry.huang@....com>
>> > ---
>> > Changes in v3:
>> >   - add new property for INCR burst in usb node.
>> >
>> >  Documentation/devicetree/bindings/usb/dwc3.txt |    5 +++++
>> >  arch/arm/boot/dts/ls1021a.dtsi                 |    1 +
>> >  arch/arm64/boot/dts/freescale/fsl-ls1043a.dtsi |    3 +++
>> >  arch/arm64/boot/dts/freescale/fsl-ls2080a.dtsi |    2 ++
>> >  4 files changed, 11 insertions(+)
>> >
>> > diff --git a/Documentation/devicetree/bindings/usb/dwc3.txt
>> > b/Documentation/devicetree/bindings/usb/dwc3.txt
>> > index e3e6983..8c405a3 100644
>> > --- a/Documentation/devicetree/bindings/usb/dwc3.txt
>> > +++ b/Documentation/devicetree/bindings/usb/dwc3.txt
>> > @@ -55,6 +55,10 @@ Optional properties:
>> >     fladj_30mhz_sdbnd signal is invalid or incorrect.
>> >
>> >   - <DEPRECATED> tx-fifo-resize: determines if the FIFO *has* to be
>> reallocated.
>> > + - snps,incr-burst-type-adjustment: Value for INCR burst type of
>> GSBUSCFG0
>> > +   register, undefined length INCR burst type enable and INCRx type.
>> > +   First field is for undefined length INCR burst type enable or not.
>> > +   Second field is for largest INCRx type enabled.
>>
>> Why do you need the first field? Is the 2nd field used if the 1st is 0?
>> If not, then just use the presence of the property to enable or not.
> The first field is one switch.
> When it is 1, means undefined length INCR burst type enabled, we can use any length less than or equal to the largest-enabled burst length of INCR4/8/16/32/64/128/256.
> When it is zero, means INCRx burst mode enabled, we can use one fixed burst length of 1/4/8/16/32/64/128/256 byte.
> So, the 2nd field is used if the 1st is 0, we need to select one largest burst length the USB controller can support.
> If we don't want to change the value of this register (use the default value), we don't need to add this property to usb node.

Just make this a single value with 0 meaning INCR and 4/8/16/etc being INCRx.

Rob