linux-kernel - Re: [PATCH v4 1/5] mtd: rawnand: meson: fix command sequence for read/write

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Message-ID: <20230522170526.6486755a@xps-13>
Date:   Mon, 22 May 2023 17:05:26 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Arseniy Krasnov <AVKrasnov@...rdevices.ru>
Cc:     Liang Yang <liang.yang@...ogic.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Kevin Hilman <khilman@...libre.com>,
        Jerome Brunet <jbrunet@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        Yixun Lan <yixun.lan@...ogic.com>,
        Jianxin Pan <jianxin.pan@...ogic.com>, <oxffffaa@...il.com>,
        <kernel@...rdevices.ru>, <linux-mtd@...ts.infradead.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-amlogic@...ts.infradead.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 1/5] mtd: rawnand: meson: fix command sequence for
 read/write

Hi Arseniy,

AVKrasnov@...rdevices.ru wrote on Mon, 15 May 2023 12:44:35 +0300:

> This fixes read/write functionality by:
> 1) Changing NFC_CMD_RB_INT bit value.

I guess this is a separate fix

> 2) Adding extra NAND_CMD_STATUS command on each r/w request.

Is this really needed? Looks like you're delaying the next op only. Is
using a delay enough? If yes, then it's probably the wrong approach.

> 3) Adding extra idle commands during r/w request.

Question about this below, might also be a patch on its own?

> 4) Adding extra NAND_CMD_READ0 on each read request.
> 
> Without this patch driver works unstable, for example there are a lot
> of ECC errors.

I believe all the fixes should be Cc'ed to stable, please add in your
commits:

Cc: stable@...

> 
> Fixes: 8fae856c5350 ("mtd: rawnand: meson: add support for Amlogic NAND flash controller")
> Suggested-by: Liang Yang <liang.yang@...ogic.com>
> Signed-off-by: Arseniy Krasnov <AVKrasnov@...rdevices.ru>
> ---
>  drivers/mtd/nand/raw/meson_nand.c | 30 +++++++++++++++++++++---------
>  1 file changed, 21 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/mtd/nand/raw/meson_nand.c b/drivers/mtd/nand/raw/meson_nand.c
> index 074e14225c06..2f4d8c84186b 100644
> --- a/drivers/mtd/nand/raw/meson_nand.c
> +++ b/drivers/mtd/nand/raw/meson_nand.c
> @@ -37,7 +37,7 @@
>  #define NFC_CMD_SCRAMBLER_ENABLE	BIT(19)
>  #define NFC_CMD_SCRAMBLER_DISABLE	0
>  #define NFC_CMD_SHORTMODE_DISABLE	0
> -#define NFC_CMD_RB_INT		BIT(14)
> +#define NFC_CMD_RB_INT ((0xb << 10) | BIT(18) | BIT(16))
>  
>  #define NFC_CMD_GET_SIZE(x)	(((x) >> 22) & GENMASK(4, 0))
>  
> @@ -392,7 +392,7 @@ 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_queue_rb(struct meson_nfc *nfc, int timeout_ms, int cmd_read0)
>  {
>  	u32 cmd, cfg;
>  	int ret = 0;
> @@ -407,17 +407,29 @@ static int meson_nfc_queue_rb(struct meson_nfc *nfc, int timeout_ms)
>  
>  	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, 5);

Why 5 and 2 below? They look like magic values. Is this totally
experimental?

> +
>  	/* use the max erase time as the maximum clock for waiting R/B */
> -	cmd = NFC_CMD_RB | NFC_CMD_RB_INT
> -		| nfc->param.chip_select | nfc->timing.tbers_max;

This is not documented in the commit log, is it?

> +	cmd = NFC_CMD_RB | NFC_CMD_RB_INT | nfc->timing.tbers_max;
>  	writel(cmd, nfc->reg_base + NFC_REG_CMD);
> +	meson_nfc_cmd_idle(nfc, 2);
>  
>  	ret = wait_for_completion_timeout(&nfc->completion,
>  					  msecs_to_jiffies(timeout_ms));
>  	if (ret == 0)
> -		ret = -1;
> +		return -1;

Please use real error codes, such as ETIMEDOUT.

>  
> -	return ret;
> +	if (!cmd_read0)
> +		return 0;
> +
> +	cmd = nfc->param.chip_select | NFC_CMD_CLE | NAND_CMD_READ0;

This looks really wrong, I don't get why you would need to send an
expensive READ0 command.

> +	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 void meson_nfc_set_user_byte(struct nand_chip *nand, u8 *oob_buf)
> @@ -623,7 +635,7 @@ 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), 1);
>  	} else {
>  		meson_nfc_cmd_idle(nfc, nfc->timing.tadl);
>  	}
> @@ -669,7 +681,7 @@ 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), 0);
>  
>  	meson_nfc_dma_buffer_release(nand, data_len, info_len, DMA_TO_DEVICE);
>  
> @@ -952,7 +964,7 @@ 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, 1);
>  			if (instr->delay_ns)
>  				meson_nfc_cmd_idle(nfc, delay_idle);
>  			break;


Thanks,
Miquèl