linux-kernel - Re: [PATCH 2/2] memory: ti-aemif: add bindings for AEMIF driver

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Date:	Mon, 9 Dec 2013 17:09:11 -0600
From:	Kumar Gala <galak@...nel.crashing.org>
To:	Grygorii Strashko <grygorii.strashko@...com>
Cc:	Ivan Khoronzhuk <ivan.khoronzhuk@...com>,
	Santosh Shilimkar <santosh.shilimkar@...com>,
	Rob Landley <rob@...dley.net>,
	Russell King <linux@....linux.org.uk>,
	devicetree <devicetree@...r.kernel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Rob Herring <rob.herring@...xeda.com>,
	Stephen Warren <swarren@...dotorg.org>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-mtd@...ts.infradead.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH 2/2] memory: ti-aemif: add bindings for AEMIF driver


On Nov 26, 2013, at 10:27 AM, Grygorii Strashko <grygorii.strashko@...com> wrote:

> On 11/22/2013 11:04 PM, Kumar Gala wrote:
>> 
>> On Nov 20, 2013, at 9:46 AM, Ivan Khoronzhuk <ivan.khoronzhuk@...com> wrote:
>> 
>>> Add bindings for AEMIF controller drivers/memory/ti-aemif.c
>>> 
>> 
>> Binding shouldn’t normally refer to code.
>> 
>> Just saying something like:
>> 
>> Adding binging for TI Async External Memory Interface (AEMIF) controller.
>> 
>> 
>>> Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@...com>
>>> ---
>>> .../bindings/memory-controllers/ti-aemif.txt       |  198 ++++++++++++++++++++
>>> 1 file changed, 198 insertions(+)
>>> create mode 100644 Documentation/devicetree/bindings/memory-controllers/ti-aemif.txt
>>> 
>>> diff --git a/Documentation/devicetree/bindings/memory-controllers/ti-aemif.txt b/Documentation/devicetree/bindings/memory-controllers/ti-aemif.txt
>>> new file mode 100644
>>> index 0000000..be0c0cb
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/memory-controllers/ti-aemif.txt
>>> @@ -0,0 +1,198 @@
>>> +* Device tree bindings for Texas instruments AEMIF controller
>>> +
>>> +Th Async External Memory Interface (EMIF16/AEMIF) controller is intended to
>> 
>> The?
>> 
>>> +provide a glue-less interface to a variety of asynchronous memory devices like
>>> +ASRA M, NOR and NAND memory. A total of 256M bytes of any of these memories
>>> +can be accessed at any given time via four chip selects with 64M byte access
>>> +per chip select. Synchronous memories such as DDR1 SD RAM, SDR SDRAM
>>> +and Mobile SDR are not supported.
>>> +
>>> +Documentation:
>>> +Davinci DM646x - http://www.ti.com/lit/ug/sprueq7c/sprueq7c.pdf
>>> +OMAP-L138 - http://www.ti.com/lit/ug/spruh77a/spruh77a.pdf
>>> +Kestone - http://www.ti.com/lit/ug/sprugz3a/sprugz3a.pdf
>>> +
>>> +Required properties:
>>> +
>>> +- compatible:		"ti,davinci-aemif"
>>> +			"ti,keystone-aemif"
>>> +			"ti,omap-L138-aemif"
>>> +
>>> +- #address-cells:	Must be 2. The first cell is the memory partition
>>> +			number. The 0 partition is for chip selects. And the
>>> +			second cell is the offset into the partition, for the 0
>>> +			partition it corresponds to chip select offset.
>>> +
>> 
>> Is the first cell just the chip select number?
> 
> No. It's rather memory range/partition number. Now there are 2 partitions:
> - control partition which is common for all CS interfaces
> - CS-specific partition/range
> (this one can be splitted according to specific SoC requirement)
> 
> As per Keystone TCI6638K2K
> Datasheet http://www.ti.com/lit/ds/sprs836d/sprs836d.pdf:
> 
> 1) the memory range 0 will be from 0x30000000 size 0x10000000:
> 00 3000 0000 - 00 33FF FFFF 64M EMIF16 CE0
> 00 3400 0000 - 00 37FF FFFF 64M EMIF16 CE1
> 00 3800 0000 - 00 3BFF FFFF 64M EMIF16 CE2
> 00 3C00 0000 - 00 3FFF FFFF 64M EMIF16 CE3
> 
> 2) the memory range 1:
> 00 2100 0A00 - 00 2100 0AFF 256 AEMIF Config
> 
> And AEMIF node contains definition:
> ranges = <0 0 0x30000000 0x10000000
> 	  1 0 0x21000A00 0x0000100>;
> 
> 
> Child node has (nand):
> reg = <0 0 0x4000000 (cs0)
>        - or - 0 0x4000000 0x4000000 (cs1)
>        - or - 0 0x8000000 0x4000000 (cs2)
> 	- or - 0 0xC000000 0x4000000 (cs3)
> 	- and -
>        1 0 0x0000100>; (for all cs)
> 
> For example for cs2 child node the resulting mem range 0 will be calculated as
> 
> from: 0x30000000 + (0 0x8000000 - 0 0)
> size: 0x4000000
> 
> We don't encode CS number in reg/ranges, because it will allow simply change 
> AEMIF DT definitions depending on each SoC
> (AEMIF CS memory range can be continuous as above or not, if not - additional
> range/partition can be added and child device can select the proper one).

This is quite confusing.  I think the ranges property needs far more description as part of the top level controller node.  It spec out what the various fields are in the ranges property.

- k--
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