Re: [PATCH v2 3/3] mtd: rawnand: meson: read/write access for boot ROM pages

On 26.08.2024 10:16, Michael Nazzareno Trimarchi wrote:
> Hi
> 
> On Mon, Aug 26, 2024 at 8:17 AM Arseniy Krasnov
> <[email protected]> wrote:
>>
>> Boot ROM on Meson needs some pages to be read/written in a special mode:
>> 384 byte ECC mode (so called "short" by Amlogic) and with scrambling
>> enabled. Such pages are located on the chip in the following way (for
>> example):
>>
>> [ p0 ][ p1 ][ p2 ][ p3 ][ p4 ][ p5 ][ p6 ][ p7 ] ... [ pN ]
>>   ^           ^           ^           ^
>>
>> pX is page number "X". "^" means "special" page used by boot ROM - e.g.
>> every 2nd page in the range of [0, 7]. Step (2 here) and last page in
>> range is read from the device tree.
>>
>> Signed-off-by: Arseniy Krasnov <[email protected]>
>> ---
>>  drivers/mtd/nand/raw/meson_nand.c | 56 +++++++++++++++++++++++++------
>>  1 file changed, 46 insertions(+), 10 deletions(-)
>>
>> diff --git a/drivers/mtd/nand/raw/meson_nand.c b/drivers/mtd/nand/raw/meson_nand.c
>> index 19f005202b..54ea035d8d 100644
>> --- a/drivers/mtd/nand/raw/meson_nand.c
>> +++ b/drivers/mtd/nand/raw/meson_nand.c
>> @@ -40,6 +40,7 @@
>>  #define NFC_CMD_RB                     BIT(20)
>>  #define NFC_CMD_SCRAMBLER_ENABLE       BIT(19)
>>  #define NFC_CMD_SCRAMBLER_DISABLE      0
>> +#define NFC_CMD_SHORTMODE_ENABLE       1
>>  #define NFC_CMD_SHORTMODE_DISABLE      0
>>  #define NFC_CMD_RB_INT                 BIT(14)
>>  #define NFC_CMD_RB_INT_NO_PIN          ((0xb << 10) | BIT(18) | BIT(16))
>> @@ -78,6 +79,8 @@
>>
>>  #define DMA_DIR(dir)           ((dir) ? NFC_CMD_N2M : NFC_CMD_M2N)
>>
>> +#define NFC_SHORT_MODE_ECC_SZ  384
>> +
>>  #define ECC_CHECK_RETURN_FF    -1
>>
>>  #define NAND_CE0               (0xe << 10)
>> @@ -141,6 +144,8 @@
>>  struct meson_nfc_nand_chip {
>>         struct list_head node;
>>         struct nand_chip nand;
>> +       u32 boot_pages;
>> +       u32 boot_page_step;
>>
>>         u32 bch_mode;
>>         u8 *data_buf;
>> @@ -229,33 +234,46 @@ static void meson_nfc_cmd_seed(const struct meson_nfc *nfc, u32 seed)
>>                nfc->reg_base + NFC_REG_CMD);
>>  }
>>
>> +static int meson_nfc_is_boot_page(struct nand_chip *nand, int page)
>> +{
>> +       const struct meson_nfc_nand_chip *meson_chip = to_meson_nand(nand);
>> +
>> +       return (nand->options & NAND_IS_BOOT_MEDIUM) &&
>> +              !(page % meson_chip->boot_page_step) &&
>> +              (page < meson_chip->boot_pages);
>> +}
>> +
>>  static void meson_nfc_cmd_access(struct nand_chip *nand, bool raw, bool dir, int page)
>>  {
>> +       const struct meson_nfc_nand_chip *meson_chip = to_meson_nand(nand);
>>         struct mtd_info *mtd = nand_to_mtd(nand);
>>         const struct meson_nfc *nfc = nand_get_controller_data(mtd_to_nand(mtd));
>> -       const struct meson_nfc_nand_chip *meson_chip = to_meson_nand(nand);
>> -       u32 bch = meson_chip->bch_mode, cmd;
>>         int len = mtd->writesize, pagesize, pages;
>>         int scrambler;
>> +       u32 cmd;
>>
>>         if (nand->options & NAND_NEED_SCRAMBLING)
>>                 scrambler = NFC_CMD_SCRAMBLER_ENABLE;
>>         else
>>                 scrambler = NFC_CMD_SCRAMBLER_DISABLE;
>>
> 
> scrambler depends on NAND_NEED_SCRAMBLING so suppose
> that is not set
> 
> scrambler = NAND_NEED_SCRAMBLING;
> 
>> -       pagesize = nand->ecc.size;
>> -
>>         if (raw) {
>>                 len = mtd->writesize + mtd->oobsize;
>>                 cmd = len | scrambler | DMA_DIR(dir);
>> -               writel(cmd, nfc->reg_base + NFC_REG_CMD);
>> -               return;
>> -       }
>> +       } else if (meson_nfc_is_boot_page(nand, page)) {
> 
> Now here you  seems that you don't care anymore about this option and check
> only meson_nfc_is_boot_page
> 
> Is something am I missing?

Idea is the following IIUC: such boot pages could be read in ECC mode only with enabled scrambling -
otherwise we get ECC error. Or we need to read it in raw mode. So:

if (read page in raw mode) {
    use scrambler as provided
} else if (read boot page in ECC mode) {
    force scrambling mode + NFC_ECC_BCH8_1K + NFC_CMD_SHORTMODE_ENABLE
} else {
    //we read non-boot page in ECC mode
   use scrambler as provided
}

Thanks


> 
> Michael
> 
>> +               pagesize = NFC_SHORT_MODE_ECC_SZ >> 3;
>> +               pages = mtd->writesize / 512;
>>
>> -       pages = len / nand->ecc.size;
>> +               scrambler = NFC_CMD_SCRAMBLER_ENABLE;
>> +               cmd = CMDRWGEN(DMA_DIR(dir), scrambler, NFC_ECC_BCH8_1K,
>> +                              NFC_CMD_SHORTMODE_ENABLE, pagesize, pages);
>> +       } else {
>> +               pagesize = nand->ecc.size >> 3;
>> +               pages = len / nand->ecc.size;
>>
>> -       cmd = CMDRWGEN(DMA_DIR(dir), scrambler, bch,
>> -                      NFC_CMD_SHORTMODE_DISABLE, pagesize, pages);
>> +               cmd = CMDRWGEN(DMA_DIR(dir), scrambler, meson_chip->bch_mode,
>> +                              NFC_CMD_SHORTMODE_DISABLE, pagesize, pages);
>> +       }
>>
>>         if (scrambler == NFC_CMD_SCRAMBLER_ENABLE)
>>                 meson_nfc_cmd_seed(nfc, page);
>> @@ -1132,6 +1150,24 @@ static int meson_nfc_nand_chip_init(struct udevice *dev, struct meson_nfc *nfc,
>>                 goto err_chip_buf_free;
>>         }
>>
>> +       if (nand->options & NAND_IS_BOOT_MEDIUM) {
>> +               ret = ofnode_read_u32(node, "amlogic,boot-pages",
>> +                                     &meson_chip->boot_pages);
>> +               if (ret) {
>> +                       dev_err(dev, "could not retrieve 'amlogic,boot-pages' property: %d",
>> +                               ret);
>> +                       goto err_chip_buf_free;
>> +               }
>> +
>> +               ret = ofnode_read_u32(node, "amlogic,boot-page-step",
>> +                                     &meson_chip->boot_page_step);
>> +               if (ret) {
>> +                       dev_err(dev, "could not retrieve 'amlogic,boot-page-step' property: %d",
>> +                               ret);
>> +                       goto err_chip_buf_free;
>> +               }
>> +       }
>> +
>>         ret = nand_register(0, mtd);
>>         if (ret) {
>>                 dev_err(dev, "'nand_register()' failed: %d\n", ret);
>> --
>> 2.30.1
>>
> 
>