linux-kernel - Re: [PATCH v6 04/10] Documentation: dt: device tree bindings for LPDDR3 memories

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Date:   Tue, 30 Apr 2019 22:04:31 +0200
From:   Lukasz Luba <l.luba@...tner.samsung.com>
To:     Rob Herring <robh@...nel.org>
Cc:     devicetree@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "open list:THERMAL" <linux-pm@...r.kernel.org>,
        linux-samsung-soc <linux-samsung-soc@...r.kernel.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Kukjin Kim <kgene@...nel.org>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Sylwester Nawrocki <s.nawrocki@...sung.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Kees Cook <keescook@...omium.org>,
        Tony Lindgren <tony@...mide.com>,
        Joerg Roedel <jroedel@...e.de>,
        Thierry Reding <treding@...dia.com>,
        Dmitry Osipenko <digetx@...il.com>, willy.mh.wolff.ml@...il.com
Subject: Re: [PATCH v6 04/10] Documentation: dt: device tree bindings for
 LPDDR3 memories

Hi Rob,

On 4/29/19 6:36 PM, Rob Herring wrote:
> On Mon, Apr 29, 2019 at 7:05 AM Lukasz Luba <l.luba@...tner.samsung.com> wrote:
>>
>> Hi Rob,
>>
>> On 4/25/19 9:51 PM, Rob Herring wrote:
>>> On Fri, Apr 19, 2019 at 04:19:22PM +0200, Lukasz Luba wrote:
>>>> The device tree bindings for LPDDR3 SDRAM memories.
>>>>
>>>> For specifying the AC timing parameters of the memory device
>>>> the 'lpddr3' binding uses binding 'lpddr2-timings'.
>>>>
>>>> Signed-off-by: Lukasz Luba <l.luba@...tner.samsung.com>
>>>> ---
>>>>    .../devicetree/bindings/lpddr3/lpddr3-timings.txt  | 57 +++++++++++++
>>>>    .../devicetree/bindings/lpddr3/lpddr3.txt          | 93 ++++++++++++++++++++++
>>>
>>> Please rename the lpddr2 directory to 'ddr' and add these to it.
>> OK, I will rename it in the nex patch set.
>>>
>>> Maybe whatever properties are common should be put in a common doc.
>> There are maybe a few common properties, but I would not dare to merge
>> lpddr2 and lpddr3 before consulting it with TI engineers who made
>> LPDDR2 support.
> 
> Why not. You aren't changing anything. Just rearranging.
True.
> 
>> Could we work on a common file after the patch set got merged?
> 
> Yes, but please still move everything to a common directory.
OK, I am currently working on it and moving these lpddr* files into
Documentation/devicetree/bindings/ddr/
Then after acceptance I will find the common stuff and do the merge.
> 
>>>
>>>>    2 files changed, 150 insertions(+)
>>>>    create mode 100644 Documentation/devicetree/bindings/lpddr3/lpddr3-timings.txt
>>>>    create mode 100644 Documentation/devicetree/bindings/lpddr3/lpddr3.txt
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/lpddr3/lpddr3-timings.txt b/Documentation/devicetree/bindings/lpddr3/lpddr3-timings.txt
>>>> new file mode 100644
>>>> index 0000000..ebf3e00
>>>> --- /dev/null
>>>> +++ b/Documentation/devicetree/bindings/lpddr3/lpddr3-timings.txt
>>>> @@ -0,0 +1,57 @@
>>>> +* AC timing parameters of LPDDR3 memories for a given speed-bin.
>>>> +* The structures are based on LPDDR2 and extended where needed.
>>>> +
>>>> +Required properties:
>>>> +- compatible : Should be "jedec,lpddr3-timings"
>>>> +- min-freq : minimum DDR clock frequency for the speed-bin. Type is <u32>
>>>> +- max-freq : maximum DDR clock frequency for the speed-bin. Type is <u32>
>>>> +
>>>> +Optional properties:
>>>> +
>>>> +The following properties represent AC timing parameters from the memory
>>>> +data-sheet of the device for a given speed-bin. All these properties are
>>>> +of type <u32> and the default unit is ps (pico seconds).
>>>> +- tRFC
>>>> +- tRRD
>>>> +- tRPab
>>>> +- tRPpb
>>>> +- tRCD
>>>> +- tRC
>>>> +- tRAS
>>>> +- tWTR
>>>> +- tWR
>>>> +- tRTP
>>>> +- tW2W-C2C
>>>> +- tR2R-C2C
>>>> +- tFAW
>>>> +- tXSR
>>>> +- tXP
>>>> +- tCKE
>>>> +- tCKESR
>>>> +- tMRD
>>>> +
>>>> +Example:
>>>> +
>>>> +timings_samsung_K3QF2F20DB_800mhz: lpddr3-timings@0 {
>>>
>>> Since the lpddr2 version was written, we've gotten stricter about
>>> allowing unit-address without reg property. Perhaps 'reg' should be the
>>> max-freq instead.
>> OK, so I will rename 'max-freq' to 'reg' and add a comment with:
>> '/* workaround: it shows max-freq */
>> Does it make sense?
> 
> Sure.
OK. Thank you.

Regards,
Lukasz
> 
> Rob
> 
>