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Date: Tue, 26 Nov 2013 17:22:03 +0800
From: Huang Shijie <b32955@freescale.com>
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To: "Gupta, Pekon" <pekon@ti.com>
Subject: Re: [PATCH] mtd: nand: auto-detection of NAND bus-width from ONFI
 param or nand_id[]
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Cc: Brian Norris <computersforpeace@gmail.com>,
 "linux-mtd@lists.infradead.org" <linux-mtd@lists.infradead.org>, "Balbi,
 Felipe" <balbi@ti.com>,
 "ezequiel.garcia@free-electrons.com" <ezequiel.garcia@free-electrons.com>,
 Artem Bityutskiy <dedekind1@gmail.com>
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=E4=BA=8E 2013=E5=B9=B411=E6=9C=8826=E6=97=A5 15:49, Gupta, Pekon =E5=86=99=
=E9=81=93:
>> From: Huang Shijie [mailto:b32955@freescale.com]
> [...]
>>> @@ -3033,6 +3028,12 @@ static int nand_flash_detect_onfi(struct
>> mtd_info *mtd, struct nand_chip *chip,
>>>    	}
>> If it is 16bit bus, could we reconfigure the bus width in here?
>> it's better to limit the influence only in the ONFI code.
>>
> Yes I too wanted same, but then once a device is found in
> nand_flash_id[] table, ONFI probe is not done ..
> Refer below code in nand_base.c
> 	@@ nand_get_flash_type()
> 	if (!type->name || !type->pagesize) {
> 			/* Check is chip is ONFI compliant */
> 			if (nand_flash_detect_onfi(mtd, chip,&busw))
>
> Thus, if we want to truly auto-detection, then we need to
> set bus-width in both cases
> (1) when NAND device is detected based on nand_flash_id[] table
If the bus-width is not the same. we'd better return with -EINVAL to tell
the user that he has a wrong configuration.

so i do not suggest we remove the -EINVAL code of nand_get_flash_type().
(I am not sure whether we should remove the NAND_BUSWIDTH_AUTO, let=20
Brian judge it)


> (2) when NAND device is detected based on ONFI probe
>
Just as suspend/resume, if we do the same thing in the ONFI probe,

we do not need to remove the -EINVAL code of the nand_get_flash_type().


thanks
Huang Shijie