linux-kernel - Re: [RFC PATCH v2 04/14] mtd: nand: define struct nand

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Message-ID: <531DC1A4.7010208@gmail.com>
Date:	Mon, 10 Mar 2014 14:44:04 +0100
From:	Boris BREZILLON <b.brezillon.dev@...il.com>
To:	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	David Woodhouse <dwmw2@...radead.org>,
	Grant Likely <grant.likely@...aro.org>,
	Brian Norris <computersforpeace@...il.com>,
	Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
	Rob Herring <rob.herring@...xeda.com>
CC:	devicetree@...r.kernel.org, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-mtd@...ts.infradead.org, dev@...ux-sunxi.org
Subject: Re: [RFC PATCH v2 04/14] mtd: nand: define struct nand_timings

Hello,

Le 29/01/2014 15:34, Boris BREZILLON a écrit :
> 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 9e6c8f9..67f0829 100644
> --- a/include/linux/mtd/nand.h
> +++ b/include/linux/mtd/nand.h
> @@ -805,4 +805,53 @@ static inline bool nand_is_slc(struct nand_chip *chip)
>   {
>   	return chip->bits_per_cell == 1;
>   }
> +
> +/**
> + * struct nand_sdr_timings - SDR NAND chip timings
> + *
> + * This struct defines the timing requirements of a SDR NAND chip.
> + * These informations can be found in every NAND datasheets and the timings
> + * meaning are described in the ONFI specifications:
> + * www.onfi.org/~/media/ONFI/specs/onfi_3_1_spec.pdf‎ (chapter 4.15 Timing
> + * Parameters)
> + *
> + */
> +
> +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 tDH_min;
> +	u32 tDS_min;
> +	u32 tFEAT_max;
> +	u32 tIR_min;
> +	u32 tITC_max;
> +	u32 tRC_min;
> +	u32 tREA_max;
> +	u32 tREH_min;
> +	u32 tRHOH_min;
> +	u32 tRHW_min;
> +	u32 tRHZ_max;
> +	u32 tRLOH_min;
> +	u32 tRP_min;
> +	u32 tRR_min;
> +	u64 tRST_max;
> +	u32 tWB_max;
> +	u32 tWC_min;
> +	u32 tWH_min;
> +	u32 tWHR_min;
> +	u32 tWP_min;
> +	u32 tWW_min;
> +};

Some timings are missing here (see Table 55 in the ONFI spec):

-tR
-tBERS
-tCCS
-tPLEBSY
-...

I see at least 3 of those timings that could be useful (for the moment) :
- tR: this one should be used to fill the chip_delay field
- tPROG and tBERS: could be used within nand_wait to choose the timeo
   value appropriately.

The problem is that these timings cannot be deduced from the ONFI timing 
mode
but should rather be extracted from other ONFI parameters or from 
specific DT
properties (hence why I didn't add them to the nand_sdr_timings struct 
int the
first place).

Should I add these fields to the nand_sdr_timings struct and change the way
onfi_async_timing_mode_to_sdr_timings works (fill a nand timing struct 
passed
as an argument instead of returning a const pointer) ?
Or should I create a new struct for these timings ?
In the latter case how should I name it ?

Best Regards,

Boris

> +
>   #endif /* __LINUX_MTD_NAND_H */

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