linux-kernel - Re: [LINUX PATCH v9 1/4] Devicetree: Add pl353 smc controller devicetree binding information

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Date:   Thu, 7 Jun 2018 17:47:27 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Naga Sureshkumar Relli <naga.sureshkumar.relli@...inx.com>
Cc:     <boris.brezillon@...tlin.com>, <richard@....at>,
        <wmw2@...radead.org>, <computersforpeace@...il.com>,
        <marek.vasut@...il.com>, <f.fainelli@...il.com>,
        <mmayer@...adcom.com>, <rogerq@...com>, <ladis@...ux-mips.org>,
        <ada@...rsis.com>, <honghui.zhang@...iatek.com>,
        <linux-mtd@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        <nagasureshkumarrelli@...il.com>
Subject: Re: [LINUX PATCH v9 1/4] Devicetree: Add pl353 smc controller
 devicetree binding information

Hi Miquel,

On Thu, 7 Jun 2018 17:42:03 +0200, Miquel Raynal
<miquel.raynal@...tlin.com> wrote:

> Hi Naga,
> 
> On Wed, 6 Jun 2018 13:19:39 +0530, Naga Sureshkumar Relli
> <naga.sureshkumar.relli@...inx.com> wrote:
> 
> > Add pl353 static memory controller devicetree binding information.
> > 
> > Signed-off-by: Naga Sureshkumar Relli <naga.sureshkumar.relli@...inx.com>
> > ---
> > Changes in v9:
> >  - Addressed commens given by Randy Dunlap and Miquel Raynal  
> 
> Can you please be more specific in your next changelog? I don't
> remember what I suggested a few months ago :)
> 
> > Changes in v8:
> >  - None
> > Changes in v7:
> > - Corrected clocks description
> > - prefixed '#' for address and size cells 
> > Changes in v6:
> >  - None
> > Changes in v5:
> >  - Removed timing properties
> > Changes in v4:
> >  - none
> > Changes in v3:
> >  - none
> > Changes in v2:
> >  - modified timing binding info as per onfi timing parameters
> >  - add suffix nano second as timing unit
> >  - modified the clock names as per the IP spec
> > ---
> >  .../bindings/memory-controllers/pl353-smc.txt      | 53 ++++++++++++++++++++++
> >  1 file changed, 53 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/memory-controllers/pl353-smc.txt
> > 
> > diff --git a/Documentation/devicetree/bindings/memory-controllers/pl353-smc.txt b/Documentation/devicetree/bindings/memory-controllers/pl353-smc.txt
> > new file mode 100644
> > index 0000000..551e66b
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/memory-controllers/pl353-smc.txt
> > @@ -0,0 +1,53 @@
> > +Device tree bindings for ARM PL353 static memory controller
> > +
> > +PL353 static memory controller supports two kinds of memory
> > +interfaces.i.e NAND and SRAM/NOR interfaces.
> > +The actual devices are instantiated from the child nodes of pl353 smc node.
> > +
> > +Required properties:
> > +- compatible		: Should be "arm,pl353-smc-r2p1"  
> 
> I thing Rob prefers:
> 
> - compatible: Must be one of:
>   * arm, pl353-smc-r2p1
> 
> > +- reg			: Controller registers map and length.
> > +- clock-names		: List of input clock names - "ref_clk", "aper_clk"
> > +			  (See clock bindings for details).
> > +- clocks		: Clock phandles (see clock bindings for details).
> > +- address-cells		: Address cells, must be 1.
> > +- size-cells		: Size cells. Must be 1.  
> 
> Please avoid padding, just this is enough:
> 
> - something: And another thing.
> 
> > +
> > +Child nodes:
> > + For NAND the "arm,pl353-nand-r2p1" and for NOR the "cfi-flash" drivers are
> > +supported as child nodes.
> > +
> > +Mandatory timing properties for child nodes:
> > +- arm,nand-cycle-t0	: Read cycle time(t_rc).
> > +- arm,nand-cycle-t1	: Write cycle time(t_wc).
> > +- arm,nand-cycle-t2	: re_n assertion delay(t_rea).
> > +- arm,nand-cycle-t3	: we_n de-assertion delay(t_wp).
> > +- arm,nand-cycle-t4	: Status read time(t_clr)
> > +- arm,nand-cycle-t5	: ID read time(t_ar)
> > +- arm,nand-cycle-t6	: busy to re_n(t_rr)  
> 
> I think this has nothing to do in the DT, you should handle timings
> from the ->setup_data_interface() hook. If you need, you may use
> different compatibles to distinguish different platform data.

Actually these are NAND-chip dependant and should be derived from the
timings given by the core in the SDR interface structure by
->setup_data_interface().