Patchwork nand_base.c: reset chip first

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Submitter karl beldan
Date Sept. 15, 2008, 12:37 p.m.
Message ID <ea2442770809150537p538f5298s9b5b003a1825b09f@mail.gmail.com>
Download mbox | patch
Permalink /patch/278/
State Accepted
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Comments

karl beldan - Sept. 15, 2008, 12:37 p.m.
Some chips require a RESET after power-up (e.g. Micron MT29FxGxxxxx).
The first command sent is NAND_CMD_READID.
Issue a NAND_CMD_RESET in nand_scan_ident before reading the device id.
Tested with an MT29F4G08AAC.

Signed-off-by: Karl Beldan <karl.beldan@gmail.com>
Ben Dooks - Sept. 16, 2008, 10:10 a.m.
On Mon, Sep 15, 2008 at 02:37:29PM +0200, Karl Beldan wrote:
> Some chips require a RESET after power-up (e.g. Micron MT29FxGxxxxx).
> The first command sent is NAND_CMD_READID.
> Issue a NAND_CMD_RESET in nand_scan_ident before reading the device id.
> Tested with an MT29F4G08AAC.

This seems sensible to me, we don't really know what state the NAND
chip is in.

Does there need to be a delay after sending the reset command before
attempting to read the chip's identity?
 
> Signed-off-by: Karl Beldan <karl.beldan@gmail.com>
> ---
> Prior to resetting, the chip gives a correct first ID byte though.
> 
> 
> diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
> index d1129ba..2cfac9b 100644
> --- a/drivers/mtd/nand/nand_base.c
> +++ b/drivers/mtd/nand/nand_base.c
> @@ -2318,6 +2318,12 @@ static struct nand_flash_dev
> *nand_get_flash_type(struct mtd_info *mtd,
>  	/* Select the device */
>  	chip->select_chip(mtd, 0);
> 
> +	/*
> +	 * Reset the chip, required by some chips (e.g. Micron MT29FxGxxxxx)
> +	 * after power-up
> +	 */
> +	chip->cmdfunc(mtd, NAND_CMD_RESET, -1, -1);
> +
>  	/* Send the command for reading device ID */
>  	chip->cmdfunc(mtd, NAND_CMD_READID, 0x00, -1);
> 
> @@ -2488,6 +2494,8 @@ int nand_scan_ident(struct mtd_info *mtd, int maxchips)
>  	/* Check for a chip array */
>  	for (i = 1; i < maxchips; i++) {
>  		chip->select_chip(mtd, i);
> +		/* See comment in nand_get_flash_type for reset */
> +		chip->cmdfunc(mtd, NAND_CMD_RESET, -1, -1);
>  		/* Send the command for reading device ID */
>  		chip->cmdfunc(mtd, NAND_CMD_READID, 0x00, -1);
>  		/* Read manufacturer and device IDs */
> 
> ______________________________________________________
> Linux MTD discussion mailing list
> http://lists.infradead.org/mailman/listinfo/linux-mtd/
karl beldan - Sept. 16, 2008, 11:55 a.m.
Ben Dooks wrote:
> On Mon, Sep 15, 2008 at 02:37:29PM +0200, Karl Beldan wrote:
>> Some chips require a RESET after power-up (e.g. Micron MT29FxGxxxxx).
>> The first command sent is NAND_CMD_READID.
>> Issue a NAND_CMD_RESET in nand_scan_ident before reading the device id.
>> Tested with an MT29F4G08AAC.
> 
> This seems sensible to me, we don't really know what state the NAND
> chip is in.
> 
> Does there need to be a delay after sending the reset command before
> attempting to read the chip's identity?
>  

There's the tWB + tRST delay which is handled by the CMD_RESET case in 
nand_command if that's what you were thinking of.
Tested both R/B and STATUS_READY code paths.

>> Signed-off-by: Karl Beldan <karl.beldan@gmail.com>
>> ---
>> Prior to resetting, the chip gives a correct first ID byte though.
>>
>>
>> diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
>> index d1129ba..2cfac9b 100644
>> --- a/drivers/mtd/nand/nand_base.c
>> +++ b/drivers/mtd/nand/nand_base.c
>> @@ -2318,6 +2318,12 @@ static struct nand_flash_dev
>> *nand_get_flash_type(struct mtd_info *mtd,
>>  	/* Select the device */
>>  	chip->select_chip(mtd, 0);
>>
>> +	/*
>> +	 * Reset the chip, required by some chips (e.g. Micron MT29FxGxxxxx)
>> +	 * after power-up
>> +	 */
>> +	chip->cmdfunc(mtd, NAND_CMD_RESET, -1, -1);
>> +
>>  	/* Send the command for reading device ID */
>>  	chip->cmdfunc(mtd, NAND_CMD_READID, 0x00, -1);
>>
>> @@ -2488,6 +2494,8 @@ int nand_scan_ident(struct mtd_info *mtd, int maxchips)
>>  	/* Check for a chip array */
>>  	for (i = 1; i < maxchips; i++) {
>>  		chip->select_chip(mtd, i);
>> +		/* See comment in nand_get_flash_type for reset */
>> +		chip->cmdfunc(mtd, NAND_CMD_RESET, -1, -1);
>>  		/* Send the command for reading device ID */
>>  		chip->cmdfunc(mtd, NAND_CMD_READID, 0x00, -1);
>>  		/* Read manufacturer and device IDs */
>>
>> ______________________________________________________
>> Linux MTD discussion mailing list
>> http://lists.infradead.org/mailman/listinfo/linux-mtd/
>

Patch

diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index d1129ba..2cfac9b 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -2318,6 +2318,12 @@  static struct nand_flash_dev
*nand_get_flash_type(struct mtd_info *mtd,
 	/* Select the device */
 	chip->select_chip(mtd, 0);

+	/*
+	 * Reset the chip, required by some chips (e.g. Micron MT29FxGxxxxx)
+	 * after power-up
+	 */
+	chip->cmdfunc(mtd, NAND_CMD_RESET, -1, -1);
+
 	/* Send the command for reading device ID */
 	chip->cmdfunc(mtd, NAND_CMD_READID, 0x00, -1);