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

[Arseniy Krasnov <avkrasnov@sberdevices.ru>]

On 23.05.2023 12:12, Arseniy Krasnov wrote:
> Hello Miquel, Liang
> 
> On 22.05.2023 18:05, Miquel Raynal wrote:
>> Hi Arseniy,
>>
>> AVKrasnov@sberdevices.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
>>
> 
> Ok, I'll move it to separate patch
> 
>>> 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.

Hi Miquel, small update, I found some details from @Liang's message in v1 talks from the last month:

*
After sending NAND_CMD_READ0, address, NAND_CMD_READSTART and read status(NAND_CMD_STATUS = 0x70) commands, it should send
NAND_CMD_READ0 command for exiting the read status mode from the datasheet from NAND device. but previous meson_nfc_queue_rb()
only checks the Ready/Busy pin and it doesn't send read status(NAND_CMD_STATUS = 0x70) command.
i think there is something wrong with the Ready/Busy pin(please check the hardware whether this
Ready/Busy pin is connected with SOC) or the source code. i have the board without Ready/Busy pin and prefer to use the
nfc command called RB_IO6. it sends NAND_CMD_STATUS command and checks bit6 of the status register of NAND device from the
data bus and generate IRQ if ready.
*

I guess, that sequence of commands from this patch is described in datasheet (unfortunately I don't have it and relied on the old driver).
Yesterday I tried to remove sending of NAND_CMD_STATUS from this patch, but it broke current driver - i had ECC errors, so it looks like
"shot in the dark" situation, to understand this logic.

Thanks, Arseniy

>>
>>> 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@...
>>
> 
> Ack, after everything will be clear with this patch :)
> 
>>>
>>> Fixes: 8fae856c5350 ("mtd: rawnand: meson: add support for Amlogic NAND flash controller")
>>> Suggested-by: Liang Yang <liang.yang@amlogic.com>
>>> Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.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?
> 
> @Liang, may be change it to defines ?
> 
>>
>>> +
>>>  	/* 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.
> 
> Ack
> 
>>
>>>  
>>> -	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.
> 
> This logic was suggested by @Liang Yang here to fix this driver (suggested as patch):
> https://lore.kernel.org/linux-mtd/8537e736-44a8-d17b-7923-25d5bd406dcc@sberdevices.ru/T/#m0df09d2ab2cac98431fb268a4ce3c00dc5c7a69e
> @Liang, could You please give us more details?
> 
> Thanks, Arseniy
> 
>>
>>> +	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