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SubjectRe: [PATCH -next v3 1/2] mtd: nand: toshiba: Retrieve ECC requirements from extended ID
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On 2017/12/07 0:08, Boris Brezillon wrote:
> On Wed, 6 Dec 2017 23:04:57 +0900
> KOBAYASHI Yoshitake <yoshitake.kobayashi@toshiba.co.jp> wrote:
>
>> This patch enables support to read the ECC strength and size from the
>> NAND flash using Toshiba Memory SLC NAND extended-ID. This patch is
>> based on the information of the 6th ID byte of the Toshiba Memory SLC
>> NAND.
>>
>> Signed-off-by: KOBAYASHI Yoshitake <yoshitake.kobayashi@toshiba.co.jp>
>> ---
>> drivers/mtd/nand/nand_toshiba.c | 28 ++++++++++++++++++++++++++++
>> 1 file changed, 28 insertions(+)
>>
>> diff --git a/drivers/mtd/nand/nand_toshiba.c b/drivers/mtd/nand/nand_toshiba.c
>> index 57df857..c2c141b 100644
>> --- a/drivers/mtd/nand/nand_toshiba.c
>> +++ b/drivers/mtd/nand/nand_toshiba.c
>> @@ -35,6 +35,34 @@ static void toshiba_nand_decode_id(struct nand_chip *chip)
>> (chip->id.data[5] & 0x7) == 0x6 /* 24nm */ &&
>> !(chip->id.data[4] & 0x80) /* !BENAND */)
>> mtd->oobsize = 32 * mtd->writesize >> 9;
>> +
>> + /*
>> + * Extract ECC requirements from 6th id byte.
>> + * For Toshiba SLC, ecc requrements are as follows:
>> + * - 43nm: 1 bit ECC for each 512Byte is required.
>> + * - 32nm: 4 bit ECC for each 512Byte is required.
>> + * - 24nm: 8 bit ECC for each 512Byte is required.
>> + */
>> + if (chip->id.len >= 6 && nand_is_slc(chip)) {
>> + chip->ecc_step_ds = 512;
>> + switch (chip->id.data[5] & 0x7) {
>> + case 0x4:
>> + chip->ecc_strength_ds = 1;
>> + break;
>> + case 0x5:
>> + chip->ecc_strength_ds = 4;
>> + break;
>> + case 0x6:
>> + chip->ecc_strength_ds = 8;
>> + break;
>> + default:
>> + WARN(1, "Could not get ECC info");
>> + chip->ecc_step_ds = 0;
>> + break;
>> + }
>> + } else if (chip->id.len < 6 && nand_is_slc(chip)) {
>> + WARN(1, "Could not get ECC info, 6th nand id byte does not exist.");
>
> I'm pretty sure you have old NAND chips that do not have 6bytes ids
> (see the table here [1]), and printing a huge backtrace in this case is
> probably not what you want.
>
> If you're okay with dropping this else block, I'll do the change when
> applying, no need to send a new version.

Some controllers may have limitation in reading ids beyond 5 bytes,
considering such scenario we think it is better to keep this warning.
However if you feel huge backtrace is an issue, how about we using pr_warn() instead?

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