linux-kernel - Re: [RFC PATCH 3/9] of: mtd: add NAND timings retrieval support

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Message-ID: <52D6BF45.80407@overkiz.com>
Date:	Wed, 15 Jan 2014 18:03:01 +0100
From:	boris brezillon <b.brezillon@...rkiz.com>
To:	Jason Gunthorpe <jgunthorpe@...idianresearch.com>
CC:	devicetree@...r.kernel.org, Russell King <linux@....linux.org.uk>,
	linux-doc@...r.kernel.org, dev@...ux-sunxi.org,
	linux-kernel@...r.kernel.org, linux-mtd@...ts.infradead.org,
	Rob Landley <rob@...dley.net>,
	Grant Likely <grant.likely@...aro.org>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	David Woodhouse <dwmw2@...radead.org>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [RFC PATCH 3/9] of: mtd: add NAND timings retrieval support

On 15/01/2014 16:09, boris brezillon wrote:
> Hello Jason,
>
> On 09/01/2014 18:35, Jason Gunthorpe wrote:
>> On Thu, Jan 09, 2014 at 09:36:18AM +0100, boris brezillon wrote:
>>
>>>> You might want to check if you can boil down the DT timings from the
>>>> huge list to just an ONFI mode number..
>>> Sure, but the sunxi driver needs at least 19 of them...
>> So does mvebu's NAND driver..
>>
>> What I ment was you could have a
>>
>>    onfi,nand-timing-mode = 0
>>
>> in the DT. Each of the modes defines all ~19 parameters, higher modes
>> are faster.
>>
>> Pick a mode value that fits all the parameters of the connected
>> non-ONFI flash.
>>
>> This would be instead of defining each parameter
>> individually.. Provide some helpers to convert from a onfi mode number
>> to all the onfi defined timing parameters so that drivers can
>> configure the HW..
>
> Are you suggesting we should provide a function that converts these
> modes into a nand_timings struct, or just use the timing modes and
> let the NAND controller drivers configure its IP accordingly ?
>
> I found the ONFI timing tables in this document:
>
> www.*onfi*.org/~/media/*ONFI*/specs/*onfi*_3_1_spec.pdf‎ (chapter 4.16).
>
> I suppose my nand_timings struct should use the names described
> page 110-111 (at least if we decide to use nand_timings and not
> nand_timing_modes), right ?

After taking a closer look at this document, the only parameter 
available in my
nand_timings struct that is not defined in the standard is tR_max (data 
transfer
from cell to register).

And the ONFI standard defines 4 more timings:
- tCEA_max
- tCEH_min
- tFEAT_max
- tITC_max



>
> Best Regards,
>
> Boris
>
>>
>> Jason
>

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