linux-kernel - Re: [PATCH v3 1/9] mtd: nand: define struct nand

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Message-ID: <536CF887.7020903@free-electrons.com>
Date:	Fri, 09 May 2014 17:47:19 +0200
From:	Boris BREZILLON <boris.brezillon@...e-electrons.com>
To:	Lee Jones <lee.jones@...aro.org>,
	Brian Norris <computersforpeace@...il.com>
CC:	devicetree@...r.kernel.org, Arnd Bergmann <arnd@...db.de>,
	linux-doc@...r.kernel.org, dev@...ux-sunxi.org,
	linux-kernel@...r.kernel.org,
	Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
	Rob Herring <robherring2@...il.com>,
	Grant Likely <grant.likely@...aro.org>,
	linux-mtd@...ts.infradead.org,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	David Woodhouse <dwmw2@...radead.org>,
	linux-arm-kernel@...ts.infradead.org,
	Lucas Stach <l.stach@...gutronix.de>
Subject: Re: [PATCH v3 1/9] mtd: nand: define struct nand_timings


On 08/05/2014 16:29, Lee Jones wrote:
>>> Define a struct containing the standard NAND timings as described in NAND
>>> datasheets.
>>>
>>> Signed-off-by: Boris BREZILLON <b.brezillon.dev@...il.com>
>>> ---
>>>  include/linux/mtd/nand.h |   49 ++++++++++++++++++++++++++++++++++++++++++++++
>>>  1 file changed, 49 insertions(+)
>>>
>>> diff --git a/include/linux/mtd/nand.h b/include/linux/mtd/nand.h
>>> index 389b3c5..f3ff3a3 100644
>>> --- a/include/linux/mtd/nand.h
>>> +++ b/include/linux/mtd/nand.h
> [...]
>
>>> + * Parameters)
>> Please document the units for these fields here. It looks like you're
>> using picoseconds.
> Can't we leave this open to interpretation?  For instance, it's more
> convenient for our driver to handle these as nano second values.
>
>>> + *
>>> + */
>>> +
>> Extra blank line.
>>
>>> +struct nand_sdr_timings {
>>> +	u32 tALH_min;
>>> +	u32 tADL_min;
>>> +	u32 tALS_min;
>>> +	u32 tAR_min;
>>> +	u32 tCEA_max;
>>> +	u32 tCEH_min;
>>> +	u32 tCH_min;
>>> +	u32 tCHZ_max;
>>> +	u32 tCLH_min;
>>> +	u32 tCLR_min;
>>> +	u32 tCLS_min;
>>> +	u32 tCOH_min;
>>> +	u32 tCS_min;
> 	u32 tCSD_min;

This is related to ddr2 timings, and this structure only define sdr
related timings.

>>> +	u32 tDH_min;
>>> +	u32 tDS_min;
>>> +	u32 tFEAT_max;
>>> +	u32 tIR_min;
>>> +	u32 tITC_max;
> 	u32 tR_max;

Actually this one cannot be retrieved from the ONFI timing mode, you'll
have to read bytes 137 and 138 in the parameter page.
Hence I got rid of it in the first place. Then I considered adding all
those missing timings in another structure (see [1]).

I noticed you posted something similar on the MTD mailing list (and
Lucas was waiting for the feature too).
Could we work together to propose something that fulfills all our needs ?

Here's what I need:
- get detailled timings to be able to configure the sunxi NAND
controller appropriately
- a way to get these timings on non-ONFi NANDs (the proposed solution is
exposing the closest  supported ONFI timing mode in the NAND chip DT
node, but I'm open to any new proposal).


Best Regards,

Boris

[1] http://lists.infradead.org/pipermail/linux-mtd/2014-March/052525.html


-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

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