Re: [RFC PATCH v1 2/2] mtd: rawnand: meson: support for 512B ECC step size

Arseniy Krasnov
2023-07-04T10:26:46Z

On 04.07.2023 12:56, Miquel Raynal wrote:
> Hi Arseniy,
>
> avkrasnov@sberdevices.ru wrote on Tue, 4 Jul 2023 12:46:51 +0300:
>
>> On 04.07.2023 12:41, Miquel Raynal wrote:
>>> Hi Arseniy,
>>>
>>> avkrasnov@sberdevices.ru wrote on Tue, 4 Jul 2023 12:23:03 +0300:
>>>
>>>> On 04.07.2023 11:36, Miquel Raynal wrote:
>>>>> Hi Arseniy,
>>>>>
>>>>> AVKrasnov@sberdevices.ru wrote on Wed, 28 Jun 2023 12:29:36 +0300:
>>>>>
>>>>>> Meson NAND supports both 512B and 1024B ECC step size.
>>>>>>
>>>>>> Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
>>>>>> ---
>>>>>> drivers/mtd/nand/raw/meson_nand.c | 47 +++++++++++++++++++++++--------
>>>>>> 1 file changed, 35 insertions(+), 12 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/mtd/nand/raw/meson_nand.c b/drivers/mtd/nand/raw/meson_nand.c
>>>>>> index 345212e8c691..6cc4f63b86c8 100644
>>>>>> --- a/drivers/mtd/nand/raw/meson_nand.c
>>>>>> +++ b/drivers/mtd/nand/raw/meson_nand.c
>>>>>> @@ -135,6 +135,7 @@ struct meson_nfc_nand_chip {
>>>>>> struct meson_nand_ecc {
>>>>>> u32 bch;
>>>>>> u32 strength;
>>>>>> + u32 size;
>>>>>> };
>>>>>>
>>>>>> struct meson_nfc_data {
>>>>>> @@ -190,7 +191,8 @@ struct meson_nfc {
>>>>>> };
>>>>>>
>>>>>> enum {
>>>>>> - NFC_ECC_BCH8_1K = 2,
>>>>>> + NFC_ECC_BCH8_512 = 1,
>>>>>> + NFC_ECC_BCH8_1K,
>>>>>> NFC_ECC_BCH24_1K,
>>>>>> NFC_ECC_BCH30_1K,
>>>>>> NFC_ECC_BCH40_1K,
>>>>>> @@ -198,15 +200,16 @@ enum {
>>>>>> NFC_ECC_BCH60_1K,
>>>>>> };
>>>>>>
>>>>>> -#define MESON_ECC_DATA(b, s) { .bch = (b), .strength = (s)}
>>>>>> +#define MESON_ECC_DATA(b, s, sz) { .bch = (b), .strength = (s), .size = (sz) }
>>>>>>
>>>>>> static struct meson_nand_ecc meson_ecc[] = {
>>>>>> - MESON_ECC_DATA(NFC_ECC_BCH8_1K, 8),
>>>>>> - MESON_ECC_DATA(NFC_ECC_BCH24_1K, 24),
>>>>>> - MESON_ECC_DATA(NFC_ECC_BCH30_1K, 30),
>>>>>> - MESON_ECC_DATA(NFC_ECC_BCH40_1K, 40),
>>>>>> - MESON_ECC_DATA(NFC_ECC_BCH50_1K, 50),
>>>>>> - MESON_ECC_DATA(NFC_ECC_BCH60_1K, 60),
>>>>>> + MESON_ECC_DATA(NFC_ECC_BCH8_512, 8, 512),
>>>>>> + MESON_ECC_DATA(NFC_ECC_BCH8_1K, 8, 1024),
>>>>>> + MESON_ECC_DATA(NFC_ECC_BCH24_1K, 24, 1024),
>>>>>> + MESON_ECC_DATA(NFC_ECC_BCH30_1K, 30, 1024),
>>>>>> + MESON_ECC_DATA(NFC_ECC_BCH40_1K, 40, 1024),
>>>>>> + MESON_ECC_DATA(NFC_ECC_BCH50_1K, 50, 1024),
>>>>>> + MESON_ECC_DATA(NFC_ECC_BCH60_1K, 60, 1024),
>>>>>> };
>>>>>>
>>>>>> static int meson_nand_calc_ecc_bytes(int step_size, int strength)
>>>>>> @@ -224,8 +227,27 @@ static int meson_nand_calc_ecc_bytes(int step_size, int strength)
>>>>>>
>>>>>> NAND_ECC_CAPS_SINGLE(meson_gxl_ecc_caps,
>>>>>> meson_nand_calc_ecc_bytes, 1024, 8, 24, 30, 40, 50, 60);
>>>>>> -NAND_ECC_CAPS_SINGLE(meson_axg_ecc_caps,
>>>>>> - meson_nand_calc_ecc_bytes, 1024, 8);
>>>>>> +
>>>>>> +static const int axg_stepinfo_strengths[] = { 8 };
>>>>>> +static const struct nand_ecc_step_info axg_stepinfo_1024 = {
>>>>>> + .stepsize = 1024,
>>>>>> + .strengths = axg_stepinfo_strengths,
>>>>>> + .nstrengths = ARRAY_SIZE(axg_stepinfo_strengths)
>>>>>> +};
>>>>>> +
>>>>>> +static const struct nand_ecc_step_info axg_stepinfo_512 = {
>>>>>> + .stepsize = 512,
>>>>>> + .strengths = axg_stepinfo_strengths,
>>>>>> + .nstrengths = ARRAY_SIZE(axg_stepinfo_strengths)
>>>>>> +};
>>>>>> +
>>>>>> +static const struct nand_ecc_step_info axg_stepinfo[] = { axg_stepinfo_1024, axg_stepinfo_512 };
>>>>>> +
>>>>>> +static const struct nand_ecc_caps meson_axg_ecc_caps = {
>>>>>> + .stepinfos = axg_stepinfo,
>>>>>> + .nstepinfos = ARRAY_SIZE(axg_stepinfo),
>>>>>> + .calc_ecc_bytes = meson_nand_calc_ecc_bytes,
>>>>>> +};
>>>>>>
>>>>>> static struct meson_nfc_nand_chip *to_meson_nand(struct nand_chip *nand)
>>>>>> {
>>>>>> @@ -1259,7 +1281,8 @@ static int meson_nand_bch_mode(struct nand_chip *nand)
>>>>>> return -EINVAL;
>>>>>>
>>>>>> for (i = 0; i < ARRAY_SIZE(meson_ecc); i++) {
>>>>>> - if (meson_ecc[i].strength == nand->ecc.strength) {
>>>>>> + if (meson_ecc[i].strength == nand->ecc.strength &&
>>>>>> + meson_ecc[i].size == nand->ecc.size) {
>>>>>> meson_chip->bch_mode = meson_ecc[i].bch;
>>>>>> return 0;
>>>>>> }
>>>>>> @@ -1278,7 +1301,7 @@ static int meson_nand_attach_chip(struct nand_chip *nand)
>>>>>> struct meson_nfc *nfc = nand_get_controller_data(nand);
>>>>>> struct meson_nfc_nand_chip *meson_chip = to_meson_nand(nand);
>>>>>> struct mtd_info *mtd = nand_to_mtd(nand);
>>>>>> - int nsectors = mtd->writesize / 1024;
>>>>>> + int nsectors = mtd->writesize / 512;
>>>>>
>>>>> This cannot be unconditional, right?
>>>>
>>>> Hello Miquel!
>>>>
>>>> Yes, this code looks strange. 'nsectors' is used to calculate space in OOB
>>>> that could be used by ECC engine (this value will be passed as 'oobavail'
>>>> to 'nand_ecc_choose_conf()'). Idea of 512 is to consider "worst" case
>>>> for ECC, e.g. minimal number of bytes for ECC engine (and at the same time
>>>> maximum number of free bytes). For Meson, if ECC step size is 512, then we
>>>> have 4 x 2 free bytes in OOB (if step size if 1024 then we have 2 x 2 free
>>>> bytes in OOB).
>>>>
>>>> I think this code could be reworked in the following way:
>>>>
>>>> if ECC step size is already known here (from DTS), calculate 'nsectors' using
>>>> given value (div by 512 for example). Otherwise calculate 'nsectors' in the
>>>> current manner:
>>>
>>> It will always be known when these function are run. There is no
>>> guessing here.
>>
>> Hm I checked, that but if step size is not set in DTS, here it will be 0,
>> then it will be selected in 'nand_ecc_choose_conf()' according provided 'ecc_caps'
>> and 'oobavail'...
>>
>> Anyway, I'll do the following thing:
>>
>> int nsectors;
>>
>> if (nand->ecc.size)
>> nsectors = mtd->writesize / nand->ecc.size; <--- this is for 512 ECC
>
> You should set nand->ecc.size in ->attach_chip() instead.

Sorry, didn't get it... if ECC step size is set in DTS, then here, in chip attach
callback it will be already known (DT part was processed in 'rawnand_dt_init()').
If ECC step size is unknown (e.g. 0 here), 'nand_ecc_choose_conf()' will set it
according provided ecc caps. What do You mean for "You should set ..." ?

Thanks, Arseniy

>
>> else
>> nsectors = mtd->writesize / 1024; <--- this is for default 1024 ECC
>>
>> Thanks, Arseniy
>>
>>>
>>>>
>>>> int nsectors = mtd->writesize / 1024;
>>>>
>>>> Moreover 1024 is default ECC step size for this driver, so default behaviour
>>>> will be preserved.
>>>
>>> Yes, otherwise you would break existing users.
>>>
>>>>
>>>> Thanks, Arseniy
>>>>
>>>>>
>>>>>> int raw_writesize;
>>>>>> int ret;
>>>>>>
>>>>>
>>>>>
>>>>> Thanks,
>>>>> Miquèl
>>>
>>>
>>> Thanks,
>>> Miquèl
>
>
> Thanks,
> Miquèl