linux-kernel - Re: R: [PATCH v3 08/11] devicetree: bindings: pci: document PARF params bindings

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Message-ID: <99f42001-0f41-5e63-f6ad-2e744ec86d36@mm-sol.com>
Date:   Wed, 13 May 2020 14:43:20 +0300
From:   Stanimir Varbanov <svarbanov@...sol.com>
To:     Rob Herring <robh@...nel.org>, ansuelsmth@...il.com
Cc:     'Bjorn Andersson' <bjorn.andersson@...aro.org>,
        'Andy Gross' <agross@...nel.org>,
        'Bjorn Helgaas' <bhelgaas@...gle.com>,
        'Mark Rutland' <mark.rutland@....com>,
        'Lorenzo Pieralisi' <lorenzo.pieralisi@....com>,
        'Andrew Murray' <amurray@...goodpenguin.co.uk>,
        'Philipp Zabel' <p.zabel@...gutronix.de>,
        linux-arm-msm@...r.kernel.org, linux-pci@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: R: [PATCH v3 08/11] devicetree: bindings: pci: document PARF
 params bindings



On 5/12/20 6:45 PM, Rob Herring wrote:
> On Thu, May 07, 2020 at 09:34:35PM +0200, ansuelsmth@...il.com wrote:
>>> On Fri, May 01, 2020 at 12:06:15AM +0200, Ansuel Smith wrote:
>>>> It is now supported the editing of Tx De-Emphasis, Tx Swing and
>>>> Rx equalization params on ipq8064. Document this new optional params.
>>>>
>>>> Signed-off-by: Ansuel Smith <ansuelsmth@...il.com>
>>>> ---
>>>>  .../devicetree/bindings/pci/qcom,pcie.txt     | 36 +++++++++++++++++++
>>>>  1 file changed, 36 insertions(+)
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/pci/qcom,pcie.txt
>>> b/Documentation/devicetree/bindings/pci/qcom,pcie.txt
>>>> index 6efcef040741..8cc5aea8a1da 100644
>>>> --- a/Documentation/devicetree/bindings/pci/qcom,pcie.txt
>>>> +++ b/Documentation/devicetree/bindings/pci/qcom,pcie.txt
>>>> @@ -254,6 +254,42 @@
>>>>  			- "perst-gpios"	PCIe endpoint reset signal line
>>>>  			- "wake-gpios"	PCIe endpoint wake signal line
>>>>
>>>> +- qcom,tx-deemph-gen1:
>>>> +	Usage: optional (available for ipq/apq8064)
>>>> +	Value type: <u32>
>>>> +	Definition: Gen1 De-emphasis value.
>>>> +		    For ipq806x should be set to 24.
>>>
>>> Unless these need to be tuned per board, then the compatible string for
>>> ipq806x should imply all these settings.
>>>
>>
>> It was requested by v2 to make this settings tunable. These don't change are
>> all the same for every ipq806x SoC. The original implementation had this 
>> value hardcoded for ipq806x. Should I restore this and drop this patch?
> 
> Yes, please.

I still think that the values for tx deemph and tx swing should be
tunable. But I can live with them in the driver if they not break
support for apq8064.

The default values in the registers for apq8064 and ipq806x are:

			default		your change
TX_DEEMPH_GEN1		21		24
TX_DEEMPH_GEN2_3_5DB	21		24
TX_DEEMPH_GEN2_6DB	32		34

TX_SWING_FULL		121		120
TX_SWING_LOW		121		120

So until now (without your change) apq8064 worked with default values.

> 
> Rob
> 

-- 
regards,
Stan