linux-kernel - Re: [PATCH 39/39] mtd: nand: denali_dt: add compatible strings for UniPhier SoC variants

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Date:   Mon, 5 Dec 2016 04:44:37 +0100
From:   Marek Vasut <marek.vasut@...il.com>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Dinh Nguyen <dinh.linux@...il.com>
Cc:     Rob Herring <robh@...nel.org>,
        "linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Boris Brezillon <boris.brezillon@...e-electrons.com>,
        Brian Norris <computersforpeace@...il.com>,
        Richard Weinberger <richard@....at>,
        David Woodhouse <dwmw2@...radead.org>,
        Cyrille Pitchen <cyrille.pitchen@...el.com>,
        Mark Rutland <mark.rutland@....com>,
        Dinh Nguyen <dinguyen@...era.com>,
        Alan Tull <atull@...nsource.altera.com>,
        Chin Liang See <clsee@...era.com>,
        Dinh Nguyen <dinguyen@...nel.org>
Subject: Re: [PATCH 39/39] mtd: nand: denali_dt: add compatible strings for
 UniPhier SoC variants

On 12/05/2016 04:30 AM, Masahiro Yamada wrote:
> Hi Dinh,
> 
> 
> 2016-12-04 7:08 GMT+09:00 Dinh Nguyen <dinh.linux@...il.com>:
>> Hi,
>>
>> On Fri, Dec 2, 2016 at 8:49 PM, Marek Vasut <marek.vasut@...il.com> wrote:
>>> On 12/03/2016 03:41 AM, Masahiro Yamada wrote:
>>>> Hi Rob,
>>>
>>> Hi!
>>>
>>>> 2016-12-03 1:26 GMT+09:00 Rob Herring <robh@...nel.org>:
>>>>
>>>>>>
>>>>>>
>>>>>> (Plan A)
>>>>>>   "denali,socfpga-nand"           (for Altera SOCFPGA variant)
>>>>>>   "denali,uniphier-nand-v1"       (for old Socionext UniPhier family variant)
>>>>>>   "denali,uniphier-nand-v2"       (for new Socionext UniPhier family variant)
>>>>>>
>>>>>> (Plan B)
>>>>>>   "altera,denali-nand"            (for Altera SOCFPGA variant)
>>>>>>   "socionext,denali-nand-v5a"     (for old Socionext UniPhier family variant)
>>>>>>   "socionext,denali-nand-v5b"     (for new Socionext UniPhier family variant)
>>>>
>>>>> Let the Altera folks worry about their stuff. At least for soft IP in
>>>>> FPGA, it's a bit of a special case. The old string can remain as bad
>>>>> as it is.
>>>>
>>>>
>>>> Hmm, I am not sure if this IP would fit in FPGA
>>>> (to use it along with NIOS-II?)
>>>>
>>>> (even if it happened, nothing of this IP would be customizable on users' side.
>>>> When buying the IP, SoC vendors submit a list of desired features.
>>>> Denali (now Cadence) generates the RTL according to the configuration sheet.
>>>> The function is fixed at this point. So, generic compatible would be
>>>> useless anyway.)
>>>>
>>>>
>>>> If we are talking about SOCFPGA,
>>>> SOCFPGA is not only FPGA. Rather "SOC" + "FPGA".
>>>> It consists of two parts:
>>>> [1] SOC part  (Cortex-A9 + various hard-wired peripherals such UART,
>>>> USB, SD, NAND, ...)
>>>> [2] FPGA part (User design logic)
>>>>
>>>> The Denali NAND controller is included in [1].
>>>> So, as far as we talk about the Denali on SOCFPGA,
>>>> it is as hard-wired as Intel, Socionext's ones.
>>>
>>> That's correct, the Denali NAND IP in altera socfpga is a hardware
>>> block. You can make it available to the fabric too, but by default
>>> it's used by the ARM part of the chip, so for this discussion, you
>>> can forget that the FPGA part exists altogether.
>>>
>>> I would be in favor of plan B, since it seems to be the more often
>>> taken approach. A nice example is ci-hdrc:
>>>
>>> $ git grep compatible drivers/usb/chipidea/
>>>
>>>>> I simply would do "socionext,uniphier-v5b-nand" (and v5a).
>>>>> The fact that it is denali is part of the documentation.
>>>>>
>>>>
>>>> Let me think about this.
>>>>
>>>> Socionext bought two version of Denali IP,
>>>> and we are now re-using the newer one (v5b) for several SoCs.
>>>> Socionext has some more product lines other than Uniphier SoC family,
>>>> perhaps wider re-use might happen in the future.
>>>>
>>>> At first, I included "uniphier" in compatible, but I am still wondering
>>>> if such a specific string is good or not.
>>>>
>>>> Also, comments from Altera engineers are appreciated.
>>
>> Sorry, it's taken me a while to add comments. My altera email is very spotty now
>> that the Intel merge is completed. Please use dinguyen@...nel.org for any future
>> communications.
>>
>> Yes, everything that is said so far for the NAND controller on the
>> SoCFPGA is correct. I added the binding for the controller a while
>> back, but unfortunately, we never added the NAND interface to the
>> devkit, so we did not do much in terms of enabling it.
>>
>> I think the only SoCFPGA board I know that has the NAND interface active is
>> the TRCom board, but I have never seen that board.
>>
>> I don't have any strong opinions on this matter, just as long as the
>> original binding
>> "denali,denali-nand-dt" is kept, and I think Rob was ok with keeping
>> that binding.
>>
> 
> I am proposing to add "altera,denali-nand" for Altera.
> For what, do you need the generic compatible?
> This IP has no default for it to fallback to.

IMO just for compatibility reasons with old DTs .
I'm also for "altera,denali-nand" or maybe "altera,socfpga-denali-nand"
to be more precise ?

-- 
Best regards,
Marek Vasut