Re: [PATCH v1] mtd: rawnand: meson: waiting w/o wired ready/busy pin

[Liang Yang]

Hi Arseniy,

On 2023/6/7 3:51, Arseniy Krasnov wrote:
> [ EXTERNAL EMAIL ]
>
> If there is no wired ready/busy pin, classic way to wait for command
> completion is to use function 'nand_soft_waitrdy()'. Meson NAND has
> special command which allows to wait for NAND_STATUS_READY bit without
> reading status in a software loop (as 'nand_soft_waitrdy()' does). To
> use it send this command along with NAND_CMD_STATUS, then wait for an
> interrupt, and after interrupt send NAND_CMD_READ0. So this feature
> allows to use interrupt driven waiting without wired ready/busy pin.
>
> Suggested-by: Liang Yang <liang.yang@xxxxxxxxxxx>
> Signed-off-by: Arseniy Krasnov <AVKrasnov@xxxxxxxxxxxxxx>
> ---
>   drivers/mtd/nand/raw/meson_nand.c | 58 ++++++++++++++++++++++++++++++-
>   1 file changed, 57 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mtd/nand/raw/meson_nand.c b/drivers/mtd/nand/raw/meson_nand.c
> index 074e14225c06..f4c5309a9527 100644
> --- a/drivers/mtd/nand/raw/meson_nand.c
> +++ b/drivers/mtd/nand/raw/meson_nand.c
> @@ -38,6 +38,7 @@
>   #define NFC_CMD_SCRAMBLER_DISABLE      0
>   #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))
>
>   #define NFC_CMD_GET_SIZE(x)    (((x) >> 22) & GENMASK(4, 0))
>
> @@ -94,6 +95,7 @@
>
>   /* nand flash controller delay 3 ns */
>   #define NFC_DEFAULT_DELAY      3000
> +#define NFC_NO_RB_PIN_DELAY    5
>
>   #define ROW_ADDER(page, index) (((page) >> (8 * (index))) & 0xff)
>   #define MAX_CYCLE_ADDRS                5
> @@ -179,6 +181,7 @@ struct meson_nfc {
>          u32 info_bytes;
>
>          unsigned long assigned_cs;
> +       bool no_rb_pin;
>   };
>
>   enum {
> @@ -392,7 +395,41 @@ static void meson_nfc_set_data_oob(struct nand_chip *nand,
>          }
>   }
>
> -static int meson_nfc_queue_rb(struct meson_nfc *nfc, int timeout_ms)
> +static int meson_nfc_wait_no_rb_pin(struct meson_nfc *nfc, int timeout_ms)
> +{
> +       u32 cmd, cfg;
> +
> +       meson_nfc_cmd_idle(nfc, nfc->timing.twb);
> +       meson_nfc_drain_cmd(nfc);
> +       meson_nfc_wait_cmd_finish(nfc, CMD_FIFO_EMPTY_TIMEOUT);
> +
> +       cfg = readl(nfc->reg_base + NFC_REG_CFG);
> +       cfg |= NFC_RB_IRQ_EN;
> +       writel(cfg, nfc->reg_base + NFC_REG_CFG);
> +
> +       reinit_completion(&nfc->completion);
> +       cmd = nfc->param.chip_select | NFC_CMD_CLE | NAND_CMD_STATUS;
> +       writel(cmd, nfc->reg_base + NFC_REG_CMD);
> +       meson_nfc_cmd_idle(nfc, NFC_NO_RB_PIN_DELAY);
> +
> +       /* use the max erase time as the maximum clock for waiting R/B */
> +       cmd = NFC_CMD_RB | NFC_CMD_RB_INT_NO_PIN | nfc->timing.tbers_max;
> +       writel(cmd, nfc->reg_base + NFC_REG_CMD);
> +       meson_nfc_cmd_idle(nfc, NFC_NO_RB_PIN_DELAY);
> +
> +       if (!wait_for_completion_timeout(&nfc->completion,
> +                                        msecs_to_jiffies(timeout_ms)))
> +               return -ETIMEDOUT;
> +
> +       cmd = nfc->param.chip_select | NFC_CMD_CLE | NAND_CMD_READ0;

NAND_CMD_READ0 should only be needed for reading operation, so we need 
skip the other operations here, such as programming and erase.

> +       writel(cmd, nfc->reg_base + NFC_REG_CMD);
> +       meson_nfc_drain_cmd(nfc);
> +       meson_nfc_wait_cmd_finish(nfc, CMD_FIFO_EMPTY_TIMEOUT);
> +
> +       return 0;
> +}
> +
> +static int meson_nfc_wait_rb_pin(struct meson_nfc *nfc, int timeout_ms)
>   {
>          u32 cmd, cfg;
>          int ret = 0;
> @@ -420,6 +457,23 @@ static int meson_nfc_queue_rb(struct meson_nfc *nfc, int timeout_ms)
>          return ret;
>   }
>
> +static int meson_nfc_queue_rb(struct meson_nfc *nfc, int timeout_ms)
> +{
> +       if (nfc->no_rb_pin) {
> +               /* This mode is used when there is no wired R/B pin.
> +                * It works like 'nand_soft_waitrdy()', but instead of
> +                * polling NAND_CMD_STATUS bit in the software loop,
> +                * it will wait for interrupt - controllers checks IO
> +                * bus and when it detects NAND_CMD_STATUS on it, it
> +                * raises interrupt. After interrupt, NAND_CMD_READ0 is
> +                * sent as terminator of the ready waiting procedure.
> +                */
> +               return meson_nfc_wait_no_rb_pin(nfc, timeout_ms);
> +       } else {
> +               return meson_nfc_wait_rb_pin(nfc, timeout_ms);
> +       }
> +}
> +
>   static void meson_nfc_set_user_byte(struct nand_chip *nand, u8 *oob_buf)
>   {
>          struct meson_nfc_nand_chip *meson_chip = to_meson_nand(nand);
> @@ -1412,6 +1466,8 @@ static int meson_nfc_probe(struct platform_device *pdev)
>                  return ret;
>          }
>
> +       nfc->no_rb_pin = !of_property_read_bool(dev->of_node, "nand-rb");
> +
>          writel(0, nfc->reg_base + NFC_REG_CFG);
>          ret = devm_request_irq(dev, irq, meson_nfc_irq, 0, dev_name(dev), nfc);
>          if (ret) {
> --
> 2.35.0