Re: [PATCH 1/3] usb: dwc3: Add reference clock properties

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Hi Felipe,

On 11/6/2018 3:26 AM, Felipe Balbi wrote:
> hi,
>
> Thinh Nguyen <thinh.nguyen@xxxxxxxxxxxx> writes:
>> Add two new device properties to program the reference clock period and
>> to enable low power management using the reference clock. This allows a
>> higher demand to go in low power for Audio Device Class devices. This
>> feature is currently only valid for DWC_usb31 peripheral controller
>> v1.80a and higher.
>>
>> Set "snps,refclk-period-ns" to program the reference clock period. The
>> valid input periods are as follow:
>>  +-------------+-----------------+
>>  | Period (ns) | Freq (MHz)      |
>>  +-------------+-----------------+
>>  | 25          | 39.7/40         |
>>  | 41          | 24.4            |
>>  | 50          | 20              |
>>  | 52          | 19.2            |
>>  | 58          | 17.2            |
>>  | 62          | 16.1            |
>>  +-------------+-----------------+
>>
>> Set "snps,refclk-lpm" to enable low power scheduling of isochronous
>> transfers by running SOF/ITP counters using the reference clock. Both
>> "snps,dis_u2_susphy_quirk" and "snps,dis_enblslpm_quirk" must not be
>> set for this feature to be enabled.
>>
>> Signed-off-by: Thinh Nguyen <thinhn@xxxxxxxxxxxx>
>> ---
>>  Documentation/devicetree/bindings/usb/dwc3.txt | 18 ++++++++++++++++++
>>  1 file changed, 18 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/usb/dwc3.txt b/Documentation/devicetree/bindings/usb/dwc3.txt
>> index 636630fb92d7..712b344c3a31 100644
>> --- a/Documentation/devicetree/bindings/usb/dwc3.txt
>> +++ b/Documentation/devicetree/bindings/usb/dwc3.txt
>> @@ -95,6 +95,24 @@ Optional properties:
>>  			this and tx-thr-num-pkt-prd to a valid, non-zero value
>>  			1-16 (DWC_usb31 programming guide section 1.2.3) to
>>  			enable periodic ESS TX threshold.
>> + - snps,refclk-period-ns: set to program the reference clock period. The valid
>> +   			input periods are as follow:
>> +			+-------------+-----------------+
>> +			| Period (ns) | Freq (MHz)      |
>> +			+-------------+-----------------+
>> +			| 25          | 39.7/40         |
>> +			| 41          | 24.4            |
>> +			| 50          | 20              |
>> +			| 52          | 19.2            |
>> +			| 58          | 17.2            |
>> +			| 62          | 16.1            |
>> +			+-------------+-----------------+
>> + - snps,enable-refclk-lpm: set to enable low power scheduling of isochronous
>> +			transfers by running SOF/ITP counters using the
>> +			reference clock. Only valid for DWC_usb31 peripheral
>> +			controller v1.80a and higher. Both
>> +			"snps,dis_u2_susphy_quirk" and
>> +			"snps,dis_enblslpm_quirk" must not be set.
> sounds like you should rely on clk API here. Then on driver call
> clk_get_rate() to computer whatever you need to compute.
>
There's nothing to compute here. We can simply enable this feature with
"snps, enable-refclk-lpm" and the controller will use the default refclk
settings.

Thinh





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