Re: [PATCH v1 2/2] mtd: rawnand: meson: waiting w/o wired ready/busy pin

[Miquel Raynal <miquel.raynal@bootlin.com>]

Hi Arseniy,

AVKrasnov@sberdevices.ru wrote on Wed, 7 Jun 2023 17:50:25 +0300:

> 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@amlogic.com>
> Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
> ---
>  drivers/mtd/nand/raw/meson_nand.c | 82 +++++++++++++++++++++++++++++--
>  1 file changed, 78 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/mtd/nand/raw/meson_nand.c b/drivers/mtd/nand/raw/meson_nand.c
> index 074e14225c06..935de8e4934d 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))
>  
> @@ -179,6 +180,7 @@ struct meson_nfc {
>  	u32 info_bytes;
>  
>  	unsigned long assigned_cs;
> +	bool no_rb_pin;
>  };
>  
>  enum {
> @@ -392,7 +394,42 @@ 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,
> +				    bool need_cmd_read0)
> +{
> +	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);
> +
> +	/* 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);
> +
> +	if (!wait_for_completion_timeout(&nfc->completion,
> +					 msecs_to_jiffies(timeout_ms)))
> +		return -ETIMEDOUT;
> +
> +	if (need_cmd_read0) {
> +		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 +457,27 @@ 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,
> +			      bool need_cmd_read0)
> +{
> +	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 if
> +		 * needed (for all cases except page programming - this
> +		 * is reason of 'need_cmd_read0' flag).
> +		 */
> +		return meson_nfc_wait_no_rb_pin(nfc, timeout_ms,
> +						need_cmd_read0);
> +	} 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);
> @@ -623,7 +681,7 @@ static int meson_nfc_rw_cmd_prepare_and_execute(struct nand_chip *nand,
>  	if (in) {
>  		nfc->cmdfifo.rw.cmd1 = cs | NFC_CMD_CLE | NAND_CMD_READSTART;
>  		writel(nfc->cmdfifo.rw.cmd1, nfc->reg_base + NFC_REG_CMD);
> -		meson_nfc_queue_rb(nfc, PSEC_TO_MSEC(sdr->tR_max));
> +		meson_nfc_queue_rb(nfc, PSEC_TO_MSEC(sdr->tR_max), true);
>  	} else {
>  		meson_nfc_cmd_idle(nfc, nfc->timing.tadl);
>  	}
> @@ -669,7 +727,7 @@ static int meson_nfc_write_page_sub(struct nand_chip *nand,
>  
>  	cmd = nfc->param.chip_select | NFC_CMD_CLE | NAND_CMD_PAGEPROG;
>  	writel(cmd, nfc->reg_base + NFC_REG_CMD);
> -	meson_nfc_queue_rb(nfc, PSEC_TO_MSEC(sdr->tPROG_max));
> +	meson_nfc_queue_rb(nfc, PSEC_TO_MSEC(sdr->tPROG_max), false);
>  
>  	meson_nfc_dma_buffer_release(nand, data_len, info_len, DMA_TO_DEVICE);
>  
> @@ -952,7 +1010,8 @@ static int meson_nfc_exec_op(struct nand_chip *nand,
>  			break;
>  
>  		case NAND_OP_WAITRDY_INSTR:
> -			meson_nfc_queue_rb(nfc, instr->ctx.waitrdy.timeout_ms);
> +			meson_nfc_queue_rb(nfc, instr->ctx.waitrdy.timeout_ms,
> +					   true);
>  			if (instr->delay_ns)
>  				meson_nfc_cmd_idle(nfc, delay_idle);
>  			break;
> @@ -1248,6 +1307,7 @@ meson_nfc_nand_chip_init(struct device *dev,
>  	struct mtd_info *mtd;
>  	int ret, i;
>  	u32 tmp, nsels;
> +	u32 nand_rb_val;
>  
>  	nsels = of_property_count_elems_of_size(np, "reg", sizeof(u32));
>  	if (!nsels || nsels > MAX_CE_NUM) {
> @@ -1287,6 +1347,20 @@ meson_nfc_nand_chip_init(struct device *dev,
>  	mtd->owner = THIS_MODULE;
>  	mtd->dev.parent = dev;
>  
> +	ret = of_property_read_u32(np, "nand-rb", &nand_rb_val);
> +	if (ret) {
> +		/* If property was not found, don't use rb pin. */
> +		if (ret == -EINVAL)
> +			nfc->no_rb_pin = true;
> +		else
> +			return -EINVAL;

You must propagate the real error code, so return ret here.

> +	} else {
> +		if (nand_rb_val)
> +			return -EINVAL;
> +
> +		nfc->no_rb_pin = false;

I expect nfc structure to be allocated with kzalloc, if that's the
case, then you don't need this line. Actually if you reset nand_rb_val
at creation time you could have something more readable, like:

	ret = of_prop(...)
	if (ret == -EINVAL)
		no_rb_pin = true;
	else if (ret)
		return ret;

	if (nand_rb_val)
		return -EINVAL;

Otherwise both patches look good to me.

> +	}
> +
>  	ret = nand_scan(nand, nsels);
>  	if (ret)
>  		return ret;


Thanks,
Miquèl