On 14/05/2022 08:24, Krishna Kurapati PSSNV wrote:
>
> On 5/12/2022 4:00 PM, Krzysztof Kozlowski wrote:
>> On 12/05/2022 07:57, Krishna Kurapati PSSNV wrote:
>>> On 5/11/2022 11:49 PM, Krzysztof Kozlowski wrote:
>>>> On 11/05/2022 17:26, Krishna Kurapati wrote:
>>>>> From: Sandeep Maheswaram <quic_c_sanm@xxxxxxxxxxx>
>>>>>
>>>>> Add device tree bindings for SNPS phy tuning parameters.
>>>>>
>>>>> Signed-off-by: Sandeep Maheswaram <quic_c_sanm@xxxxxxxxxxx>
>>>>> Signed-off-by: Krishna Kurapati <quic_kriskura@xxxxxxxxxxx>
>>>>> ---
>>>>> .../bindings/phy/qcom,usb-snps-femto-v2.yaml | 87 ++++++++++++++++++++++
>>>>> 1 file changed, 87 insertions(+)
>>>>>
>>>>> diff --git a/Documentation/devicetree/bindings/phy/qcom,usb-snps-femto-v2.yaml b/Documentation/devicetree/bindings/phy/qcom,usb-snps-femto-v2.yaml
>>>>> index 1ce251d..70efffe 100644
>>>>> --- a/Documentation/devicetree/bindings/phy/qcom,usb-snps-femto-v2.yaml
>>>>> +++ b/Documentation/devicetree/bindings/phy/qcom,usb-snps-femto-v2.yaml
>>>>> @@ -53,6 +53,93 @@ properties:
>>>>> vdda33-supply:
>>>>> description: phandle to the regulator 3.3V supply node.
>>>>>
>>>>> + qcom,hs-disconnect-bps:
>>>>> + $ref: /schemas/types.yaml#/definitions/int32
>>>>> + description:
>>>>> + This adjusts the voltage level for the threshold used to
>>>>> + detect a disconnect event at the host. Possible values are.
>>>>> + The values defined are in multiples of basis points (1bp = 0.01%).
>>>> This means there is some minimum and maximum (100%)?
>>> Hi Krzystof,
>>>
>>> Yes there are max and min for each parameter (not necessarily 0%/100%)
>>>
>>> As an example if we take squelch detector threshold, the register value
>>> vs actual percentage changer as per data book is as follows :
>>>
>>> % change in voltage | corresponding reg value
>>>
>>> -20.90% | 7
>>> -15.60% | 6
>>> -10.30% | 5
>>> -5.30% | 4
>>> 0% | 3
>>> 5.30% | 2
>>> 10.60% | 1
>>> 15.90% | 0
>>>
>>> Here the min and max are 15.9% to -20.9%
>>>
>>> The min and max differ for each parameter and might not be necessarily
>>> 0% and 100%
>> Then it seems possible to define minimum and maximum values - please add
>> them ("minimum: xxxx").
>>
>>
>> Best regards,
>> Krzysztof
>
> Hi Krzysztof,
>
> Sorry for the late reply, missed this mail.
>
> Currently, these values have a fixed maximum and minimum. But if these
> limits change in the
>
> future (say on a per target basis) , would it be appropriate to add them
> here in bindings file ?
Per "target" you mean compatible? Then yes, the same as customizing
number of interrupts, clocks etc.
>
> Also in the driver file for sc7280 target, we have added parameter
> mapping : (map b/w register value
>
> and bps passed from device tree). For squelch detector, it is as follows:
>
> +static struct override_param squelch_det_threshold_sc7280[] = {
> + OVERRIDE_PARAM(-2090, 7),
> + OVERRIDE_PARAM(-1560, 6),
> + OVERRIDE_PARAM(-1030, 5),
> + OVERRIDE_PARAM(-530, 4),
> + OVERRIDE_PARAM(0, 3),
> + OVERRIDE_PARAM(530, 2),
> + OVERRIDE_PARAM(1060, 1),
> + OVERRIDE_PARAM(1590, 0),
> +};
>
> And the code is written such that if we give a bps value in dt greater than max value in
> table, we would automatically choose max value. And if we provide bps value lesser than
> minimum value, we would choose the min value.
>
> So, would it be appropriate to add the min and max in dt-bindings when there is a
> slight chance of them changing in the future ?
The kernel behavior should not matter here, because the bindings are
about the hardware. Therefore if hardware comes with maximum/minimum
values, it would be better to document them here.
Best regards,
Krzysztof
