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

[Liang Yang]

Hi Arseniy,

On 2023/6/7 3:54, Arseniy Krasnov wrote:
> [ EXTERNAL EMAIL ]
>
> On 06.06.2023 22:51, Arseniy Krasnov wrote:
> > 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);
>
> ^^^
> Liang, I've implemented "new RB_INT" way instead of 'nand_soft_waitrdy()'. There were two numbers
> 2 and 5 in 'meson_nfc_cmd_idle()' as time argument (here and above). I've replaced both with
> define of 5 == NFC_NO_RB_PIN_DELAY. Is it correct? 2 and 5 were from doc?

You can do like that. as i know, bigger has no impact.
yes, them come from the example code of the controller datasheet; but i 
think we can delete them also.

> Thanks, Arseniy
>
> > +
> > +     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;
> > +     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) {