linux-kernel - Re: [PATCH v6 1/2] mtd: arasan: Add device tree binding documentation

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Date:   Mon, 5 Dec 2016 17:11:36 +0100
From:   Marek Vasut <marek.vasut@...il.com>
To:     Boris Brezillon <boris.brezillon@...e-electrons.com>
Cc:     Punnaiah Choudary Kalluri <punnaiah.choudary.kalluri@...inx.com>,
        dwmw2@...radead.org, computersforpeace@...il.com, richard@....at,
        cyrille.pitchen@...el.com, robh+dt@...nel.org,
        mark.rutland@....com, linux-kernel@...r.kernel.org,
        linux-mtd@...ts.infradead.org, devicetree@...r.kernel.org,
        michals@...inx.com, kalluripunnaiahchoudary@...il.com,
        kpc528@...il.com, Punnaiah Choudary Kalluri <punnaia@...inx.com>
Subject: Re: [PATCH v6 1/2] mtd: arasan: Add device tree binding documentation

On 12/05/2016 09:36 AM, Boris Brezillon wrote:
> On Mon, 5 Dec 2016 05:25:54 +0100
> Marek Vasut <marek.vasut@...il.com> wrote:
> 
>> On 12/05/2016 05:11 AM, Punnaiah Choudary Kalluri wrote:
>>> This patch adds the dts binding document for arasan nand flash
>>> controller.
>>>
>>> Signed-off-by: Punnaiah Choudary Kalluri <punnaia@...inx.com>
>>> Acked-by: Rob Herring <robh@...nel.org>
>>> ---
>>> changes in v6:
>>> - Removed num-cs property
>>> - Separated nandchip from nand controller
>>> changes in v5:
>>> - None
>>> Changes in v4:
>>> - Added num-cs property
>>> - Added clock support
>>> Changes in v3:
>>> - None
>>> Changes in v2:
>>> - None
>>> ---
>>>  .../devicetree/bindings/mtd/arasan_nfc.txt         | 38 ++++++++++++++++++++++
>>>  1 file changed, 38 insertions(+)
>>>  create mode 100644 Documentation/devicetree/bindings/mtd/arasan_nfc.txt
>>>
>>> diff --git a/Documentation/devicetree/bindings/mtd/arasan_nfc.txt b/Documentation/devicetree/bindings/mtd/arasan_nfc.txt
>>> new file mode 100644
>>> index 0000000..dcbe7ad
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/mtd/arasan_nfc.txt
>>> @@ -0,0 +1,38 @@
>>> +Arasan Nand Flash Controller with ONFI 3.1 support  
>>
>> Arasan NAND Flash ...
>>
>>> +Required properties:
>>> +- compatible: Should be "arasan,nfc-v3p10"  
>>
>> This v3p10 looks like version 3 patchlevel 10, but shouldn't we have
>> some fallback option which doesn't encode IP version in the compat
>> string ?
> 
> Not necessarily. Usually you define a generic compatible when you have
> other reliable means to detect the IP version (a version register for
> example).
> If you can't detect that at runtime, then providing only specific
> compatible strings is a good solution to avoid breaking the DT ABI.

Can we detect it at runtime with this hardware ?

>>
>> Also, shouldn't quirks be handled by DT props instead of effectively
>> encoding them into the compatible string ?
> 
> Well, from my experience, it's better to hide as much as possible
> behind the compatible. This way, if new quirks are needed for a
> specific revision, you can update the driver without having to change
> the DT.

That's a good point, yes.

-- 
Best regards,
Marek Vasut