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

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Date:   Mon, 5 Dec 2016 13:56:51 +0000
From:   Punnaiah Choudary Kalluri <punnaiah.choudary.kalluri@...inx.com>
To:     Boris Brezillon <boris.brezillon@...e-electrons.com>,
        Marek Vasut <marek.vasut@...il.com>
CC:     "dwmw2@...radead.org" <dwmw2@...radead.org>,
        "computersforpeace@...il.com" <computersforpeace@...il.com>,
        "richard@....at" <richard@....at>,
        "cyrille.pitchen@...el.com" <cyrille.pitchen@...el.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Michal Simek <michals@...inx.com>,
        "kalluripunnaiahchoudary@...il.com" 
        <kalluripunnaiahchoudary@...il.com>,
        "kpc528@...il.com" <kpc528@...il.com>
Subject: RE: [PATCH v6 1/2] mtd: arasan: Add device tree binding
 documentation



> -----Original Message-----
> From: Boris Brezillon [mailto:boris.brezillon@...e-electrons.com]
> Sent: Monday, December 05, 2016 2:07 PM
> To: Marek Vasut <marek.vasut@...il.com>
> Cc: Punnaiah Choudary Kalluri <punnaia@...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; Michal Simek <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 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.

Yes. I am also thinking the same. Arasan controller doesn't have the register
to indicate the IP version number.

> 
> >
> > 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.
> 

Agree.

Regards,
Punnaiah

> >
> > > +- reg: Memory map for module access
> > > +- interrupt-parent: Interrupt controller the interrupt is routed
> > > +through
> > > +- interrupts: Should contain the interrupt for the device
> > > +- clock-name: List of input clocks - "clk_sys", "clk_flash"
> > > +	      (See clock bindings for details)
> > > +- clocks: Clock phandles (see clock bindings for details)
> > > +
> > > +Optional properties:
> > > +- arasan,has-mdma: Enables Dma support
> >
> > 'Enables DMA support' , with DMA in caps.
> >
> > > +for nand partition information please refer the below file
> >
> > For NAND ...
> >
> > > +Documentation/devicetree/bindings/mtd/partition.txt
> > > +
> > > +Example:
> > > +	nand0: nand@...00000 {
> > > +		compatible = "arasan,nfc-v3p10"
> > > +		reg = <0x0 0xff100000 0x1000>;
> > > +		clock-name = "clk_sys", "clk_flash"
> > > +		clocks = <&misc_clk &misc_clk>;
> > > +		interrupt-parent = <&gic>;
> > > +		interrupts = <0 14 4>;
> > > +		arasan,has-mdma;
> > > +		#address-cells = <1>;
> > > +		#size-cells = <0>
> > > +
> > > +		nand@0 {
> > > +			reg = <0>
> > > +			partition@0 {
> > > +				label = "filesystem";
> > > +				reg = <0x0 0x0 0x1000000>;
> > > +			};
> > > +			(...)
> > > +		};
> > > +	};
> > >
> >
> >