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SubjectRe: [PATCH -next v3 1/2] mtd: nand: toshiba: Retrieve ECC requirements from extended ID
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On 2017/12/27 15:06, KOBAYASHI Yoshitake wrote:
> On 2017/12/19 20:56, Boris Brezillon wrote:
>> On Tue, 19 Dec 2017 20:42:36 +0900
>> KOBAYASHI Yoshitake <yoshitake.kobayashi@toshiba.co.jp> wrote:
>>
>>> 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?
>>>
>>
>> Toshiba NANDs with an id smaller than 6 bytes exist, so no, we should
>> not complain at all. If the controller is broken and can't read the 8 id
>> bytes the core is asking for, then it should be detected at the core
>> level not in the NAND manufacturer driver.
>
> I understood your opinion. Please apply this patch with dropping the else block.

Should I repost patch with else block dropped? Please let me know if that is necessary.

-- Yoshi

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