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Re: [PATCH 2/2] usb: dwc3: Added a property to set GFLADJ register

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  Re: [PATCH 2/2] usb: dwc3: Added a property to set GFLADJ register Rob Herring <robh@kernel.org> - 2016-09-12 17:40 +0200
    Re: [PATCH 2/2] usb: dwc3: Added a property to set GFLADJ register Felipe Balbi <balbi@kernel.org> - 2016-09-13 07:50 +0200
    Re: [PATCH 2/2] usb: dwc3: Added a property to set GFLADJ register John Youn <John.Youn@synopsys.com> - 2016-09-13 21:20 +0200

#1481452 — Re: [PATCH 2/2] usb: dwc3: Added a property to set GFLADJ register

On Thu, Sep 01, 2016 at 02:32:33PM -0700, John Youn wrote:
> From: Thinh Nguyen <thinhn@synopsys.com>
> 
> Added gfladj variable to control the core behavior with respect to
> SOF, ITP, and frame timer functionality.
> 
> Currently there is dwc->fladj that holds a single field in GFLADJ
> register (GFLADJ.GFLADJ_30MHZ). A new variable gfladj is added to
> dwc structure to allow setting of the entire GFLADJ register. If
> dwc->gfladj is set, then it has a higher priority than dwc->fladj
> when writing to the GFLADJ register.

I'm not a fan of magic register values for DT properties.

How many fields in this register that you will ever need to touch?

> Synopsys HW setup (HAPS DX and phy board) requires a preset to this
> register to improve interoperablitity. For example, the value for
> GFLADJ_REFCLK_LPM_SEL should be set to 0 with ref_clk period of 50.

This sounds like it should be handled in the driver. Is it a simple, 
constant correlation of ref_clk period to this value?

> 
> Signed-off-by: Thinh Nguyen <thinhn@synopsys.com>
> Signed-off-by: John Youn <johnyoun@synopsys.com>
> ---
>  Documentation/devicetree/bindings/usb/dwc3.txt | 2 ++
>  drivers/usb/dwc3/core.c                        | 5 +++++
>  drivers/usb/dwc3/core.h                        | 1 +
>  drivers/usb/dwc3/dwc3-pci.c                    | 1 +
>  4 files changed, 9 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/usb/dwc3.txt b/Documentation/devicetree/bindings/usb/dwc3.txt
> index aa54ba7..cad4bf6 100644
> --- a/Documentation/devicetree/bindings/usb/dwc3.txt
> +++ b/Documentation/devicetree/bindings/usb/dwc3.txt
> @@ -52,6 +52,8 @@ Optional properties:
>     UTMI+ and "ulpi" for ULPI when the DWC_USB3_HSPHY_INTERFACE has value 3.
>   - snps,ref_clk_per: value for GUTCL.RefClkPer field that sets the period of
>  			ref_clk in nano seconds.
> + - snps,gfladj: if set, overides the value in the GFLADJ register. Takes
> + 			precedence over snps,quirk-frame-length-adjustment.
>   - snps,quirk-frame-length-adjustment: Value for GFLADJ_30MHZ field 
of GFLADJ
>  	register for post-silicon frame length adjustment when the
>  	fladj_30mhz_sdbnd signal is invalid or incorrect.

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#1482149

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Hi,

Rob Herring <robh@kernel.org> writes:
>> Synopsys HW setup (HAPS DX and phy board) requires a preset to this
>> register to improve interoperablitity. For example, the value for
>> GFLADJ_REFCLK_LPM_SEL should be set to 0 with ref_clk period of 50.
>
> This sounds like it should be handled in the driver. Is it a simple, 
> constant correlation of ref_clk period to this value?

you mean that this could be calculated based off of clk_get_rate() ?

-- 
balbi

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#1482719

On 9/12/2016 8:30 AM, Rob Herring wrote:
> On Thu, Sep 01, 2016 at 02:32:33PM -0700, John Youn wrote:
>> From: Thinh Nguyen <thinhn@synopsys.com>
>>
>> Added gfladj variable to control the core behavior with respect to
>> SOF, ITP, and frame timer functionality.
>>
>> Currently there is dwc->fladj that holds a single field in GFLADJ
>> register (GFLADJ.GFLADJ_30MHZ). A new variable gfladj is added to
>> dwc structure to allow setting of the entire GFLADJ register. If
>> dwc->gfladj is set, then it has a higher priority than dwc->fladj
>> when writing to the GFLADJ register.
> 
> I'm not a fan of magic register values for DT properties.
> 

Sure. Felipe gave the same feedback. We'll fix it.

> How many fields in this register that you will ever need to touch?
> 
>> Synopsys HW setup (HAPS DX and phy board) requires a preset to this
>> register to improve interoperablitity. For example, the value for
>> GFLADJ_REFCLK_LPM_SEL should be set to 0 with ref_clk period of 50.
> 
> This sounds like it should be handled in the driver. Is it a simple, 
> constant correlation of ref_clk period to this value?

I don't know. I'll look into it.

Regards,
John

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