Re: [PATCH v2 12/25] dt-bindings: qcom_nandc: QPIC NAND documentation

[Abhishek Sahu]

On 2017-08-04 18:15, Boris Brezillon wrote:
> On Mon, 31 Jul 2017 21:35:57 +0530
> Abhishek Sahu <absahu@xxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxx>
> > >>> ---
> > >>>  .../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.

 Thanks Boris for detailed clarification.
 Then I will change the patch to use SoC specific compatible string.

 Its better to use qcom,ipq4019 for 1.4.0 and qcom,ipq8074 for 1.5.0
 since we don't have other SoC in upstream and I have tested the
 NAND driver on these IPQ SoC's.