linux-kernel - Re: [PATCH v2 12/25] dt-bindings: qcom

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Message-ID: <20170804144536.4177a12f@bbrezillon>
Date:   Fri, 4 Aug 2017 14:45:36 +0200
From:   Boris Brezillon <boris.brezillon@...e-electrons.com>
To:     Abhishek Sahu <absahu@...eaurora.org>
Cc:     Rob Herring <robh@...nel.org>, dwmw2@...radead.org,
        computersforpeace@...il.com, marek.vasut@...il.com, richard@....at,
        cyrille.pitchen@...ev4u.fr, mark.rutland@....com,
        linux-mtd@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        andy.gross@...aro.org, architt@...eaurora.org,
        sricharan@...eaurora.org
Subject: Re: [PATCH v2 12/25] dt-bindings: qcom_nandc: QPIC NAND
 documentation

On Mon, 31 Jul 2017 21:35:57 +0530
Abhishek Sahu <absahu@...eaurora.org> wrote:

> On 2017-07-26 00:13, Abhishek Sahu wrote:
> > On 2017-07-25 00:47, Rob Herring wrote:  
> >> On Wed, Jul 19, 2017 at 05:18:00PM +0530, Abhishek Sahu wrote:  
> >>> 1. QPIC NAND will use compatible string "qcom,qpic-nandc-v1.4.0"
> >>> 2. QPIC NAND will 3 BAM channels: command, data tx and data rx
> >>>    while EBI2 NAND uses only single ADM channel.
> >>> 3. CRCI is only required for ADM DMA and its not required for
> >>>    QPIC NAND.
> >>> 
> >>> Signed-off-by: Abhishek Sahu <absahu@...eaurora.org>
> >>> ---
> >>>  .../devicetree/bindings/mtd/qcom_nandc.txt         | 54 
> >>> ++++++++++++++++++++--
> >>>  1 file changed, 51 insertions(+), 3 deletions(-)
> >>> 
> >>> diff --git a/Documentation/devicetree/bindings/mtd/qcom_nandc.txt 
> >>> b/Documentation/devicetree/bindings/mtd/qcom_nandc.txt
> >>> index b24adfe..8efaeb0 100644
> >>> --- a/Documentation/devicetree/bindings/mtd/qcom_nandc.txt
> >>> +++ b/Documentation/devicetree/bindings/mtd/qcom_nandc.txt
> >>> @@ -1,13 +1,15 @@
> >>>  * Qualcomm NAND controller
> >>> 
> >>>  Required properties:
> >>> -- compatible:		should be "qcom,ebi2-nandc" - EBI2 NAND which uses 
> >>> ADM
> >>> -			DMA like IPQ8064.
> >>> -
> >>> +- compatible:		must be one of the following:
> >>> +	* "qcom,ebi2-nandc" - EBI2 NAND which uses ADM DMA like IPQ8064.
> >>> +	* "qcom,qpic-nandc-v1.4.0" - QPIC NAND v1.4.0 which uses BAM DMA 
> >>> like IPQ4019.  
> >> 
> >> Looks like you have 2 SoCs and 2 versions of h/w. Use SoC specific
> >> compatible strings.  
> > 
> >  We have 3 versions of NAND HW currently.
> >  EBI2,
> >  QPIC version 1.4.0
> >  QPIC version 1.5.0
> > 
> >  and multiple Qualcomm SoCs which use any one of these.
> > 
> >  The original plan was to have compatible string for NAND version since
> >  same NAND hardware is being in different SoC and SoC dtsi will simply
> >  use its NAND version compatible string like other Qualcomm hardwares
> > 
> > 
> > http://elixir.free-electrons.com/linux/latest/source/Documentation/devicetree/bindings/dma/qcom_bam_dma.txt
> > 
> > http://elixir.free-electrons.com/linux/latest/source/Documentation/devicetree/bindings/spi/qcom,spi-qup.txt
> >   
> 
>   Following are the partial list for NAND controller and supported
>   SoC
> 
>    EBI2:          IPQ8064, APQ8064, MSM7xx, MDM9x15
>    QPIC v1.4.0    MDM9x25, MDM9x35, MDM9x45, IPQ4019
>    QPIC v1.5.0    MDM9x55, IPQ8074
> 
>   so could we use NAND controller specific compatible strings instead of 
> SoC
>   since it will easy to maintain?

Nope, though you can re-use the compatible of an old SoC for new SoCs
if the IP did not change.

For example:

- EBI2: compatible = "qcom,ipq8064"
- QPIC 1.4: compatible = "qcom,mdm9x25"
- QPIC 1.5: compatible = "qcom,mdm9x55"

Note that we usually pick the oldest SoC that started embedding an IP
when choosing the compatible. So my suggestion assumes IPQ8064 is older
than APQ8064, MSM7xx and MDM9x15.