linux-kernel - Re: [PATCH] phy: qcom-qmp: Fix dts bindings to reflect reality

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Date:   Fri, 20 Jul 2018 08:13:44 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Rob Herring <robh@...nel.org>
Cc:     Kishon Vijay Abraham I <kishon@...com>,
        Mark Rutland <mark.rutland@....com>,
        devicetree@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        Vivek Gautam <vivek.gautam@...eaurora.org>,
        Manu Gautam <mgautam@...eaurora.org>,
        Varadarajan Narayanan <varada@...eaurora.org>
Subject: Re: [PATCH] phy: qcom-qmp: Fix dts bindings to reflect reality

Rob,

On Fri, Jul 20, 2018 at 7:10 AM, Rob Herring <robh@...nel.org> wrote:
> On Fri, Jul 06, 2018 at 04:31:42PM -0700, Douglas Anderson wrote:
>> A few patches have landed for the qcom-qmp PHY that affect how you
>> would write a device tree node.  ...yet the bindings weren't updated.
>> Let's remedy the situation and make the bindings refelect reality.
>
> "dt-bindings: phy: ..." for the subject.

Sorry.  Every subsystem has different conventions for this so I
usually just do a "git log" on the file and make my best guess.  I'll
try to remember this for next time though.

In this case, though, it looks like this already landed.  I see this
patch in Kishon's next branch.

>> Fixes: efb05a50c956 ("phy: qcom-qmp: Add support for QMP V3 USB3 PHY")
>> Fixes: ac0d239936bd ("phy: qcom-qmp: Add support for runtime PM")
>> Signed-off-by: Douglas Anderson <dianders@...omium.org>
>> ---
>>
>>  .../devicetree/bindings/phy/qcom-qmp-phy.txt       | 14 ++++++++++++--
>>  1 file changed, 12 insertions(+), 2 deletions(-)
>>
>> diff --git a/Documentation/devicetree/bindings/phy/qcom-qmp-phy.txt b/Documentation/devicetree/bindings/phy/qcom-qmp-phy.txt
>> index 266a1bb8bb6e..0c7629e88bf3 100644
>> --- a/Documentation/devicetree/bindings/phy/qcom-qmp-phy.txt
>> +++ b/Documentation/devicetree/bindings/phy/qcom-qmp-phy.txt
>> @@ -12,7 +12,14 @@ Required properties:
>>              "qcom,sdm845-qmp-usb3-phy" for USB3 QMP V3 phy on sdm845,
>>              "qcom,sdm845-qmp-usb3-uni-phy" for USB3 QMP V3 UNI phy on sdm845.
>>
>> - - reg: offset and length of register set for PHY's common serdes block.
>> + - reg:
>> +   - For "qcom,sdm845-qmp-usb3-phy":
>> +     - index 0: address and length of register set for PHY's common serdes
>> +       block.
>> +     - named register "dp_com" (using reg-names): address and length of the
>> +       DP_COM control block.
>
> You need to list reg-names and what are the names for the other 2
> regions?

Here's the code works.  You can tell me how you want this expressed in
the bindings:

* In all cases the driver maps its main memory range (for the common
serdes block) without specifying any name.  This is equivalent to
asking for index 0.

* For "qcom,sdm845-qmp-usb3-phy" the driver requests a second memory
range by name using the name "dp_com".

...basically the driver is inconsistent between using names and
indices and I was trying to document that fact.

I guess options:

1. I could reword this so it's clearer (open to suggestions)

2. I could add something to the bindings saying that the first reg
name should be "reg-base" or something.  Then the question is whether
we should go to the code and start enforcing that.  If we do choose to
enforce it then it's technically breaking compatibility (though I
doubt there is any real dts in the wild).  If we don't choose to
enforce it then why did we bother saying what it should be named?

Anyway, let me know.  As I said above, Kishon already applied this
change but I'm happy to post a followup.

-Doug