linux-kernel - Re: [PATCH v1] mtd: rawnand: Add Macronix NAND read retry support

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Date:   Fri, 10 May 2019 09:45:28 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Mason Yang <masonccyang@...c.com.tw>
Cc:     bbrezillon@...nel.org, marek.vasut@...il.com,
        linux-kernel@...r.kernel.org, richard@....at, dwmw2@...radead.org,
        computersforpeace@...il.com, linux-mtd@...ts.infradead.org,
        juliensu@...c.com.tw
Subject: Re: [PATCH v1] mtd: rawnand: Add Macronix NAND read retry support

Hi Mason,

Mason Yang <masonccyang@...c.com.tw> wrote on Fri, 10 May 2019 15:41:02
+0800:

> Add a driver for Macronix NAND read retry.

"Add support for Macronix NAND read retry."? This is not a "new driver".

> 
> Macronix NAND supports specfical read for data recovery and enabled


Macronix NANDs support specific read operation for data recovery,
which can be enabled with a SET_FEATURE.

> Driver check byte 167 of Vendor Blocks in ONFI parameter page table

         checks

> to see if this high reliability function is support or not.

                 high-reliability function? not sure it is English
                 anyway.

                                              supported

> 
> Signed-off-by: Mason Yang <masonccyang@...c.com.tw>
> ---
>  drivers/mtd/nand/raw/nand_macronix.c | 52 ++++++++++++++++++++++++++++++++++++
>  1 file changed, 52 insertions(+)
> 
> diff --git a/drivers/mtd/nand/raw/nand_macronix.c b/drivers/mtd/nand/raw/nand_macronix.c
> index 47d8cda..5cd1e5f 100644
> --- a/drivers/mtd/nand/raw/nand_macronix.c
> +++ b/drivers/mtd/nand/raw/nand_macronix.c
> @@ -17,6 +17,57 @@
>  
>  #include "internals.h"
>  
> +#define MACRONIX_READ_RETRY_BIT BIT(0)
> +#define MACRONIX_READ_RETRY_MODE 5
> +
> +struct nand_onfi_vendor_macronix {
> +	u8 reserved[1];
> +	u8 reliability_func;
> +} __packed;
> +
> +static int macronix_nand_setup_read_retry(struct nand_chip *chip, int mode)
> +{
> +	u8 feature[ONFI_SUBFEATURE_PARAM_LEN] = {0};

                                                 0 is not needed here

> +	int ret;
> +
> +	if (mode > MACRONIX_READ_RETRY_MODE)
> +		mode = MACRONIX_READ_RETRY_MODE;
> +
> +	feature[0] = mode;
> +	ret =  nand_set_features(chip, ONFI_FEATURE_ADDR_READ_RETRY, feature);

Don't you miss to select/deselect the target?

> +	if (ret)
> +		pr_err("set feature failed to read retry moded:%d\n", mode);

                       "Failed to set read retry mode: %d\n"

I think you can abort the operation with a negative return code in this
case.

> +
> +	ret =  nand_get_features(chip, ONFI_FEATURE_ADDR_READ_RETRY, feature);

If the operation succeeded but the controller cannot get the feature
you don't want to abort the operation. You should check if get_features
is supported, if yes you can rely on the below test.

> +	if (ret || feature[0] != mode)
> +		pr_err("get feature failed to read retry moded:%d(%d)\n",
> +		       mode, feature[0]);

                       "Failed to verify read retry mode..."

                Also return something negative here.

> +
> +	return ret;

And if all went right, return 0 at the end.

> +}
> +
> +static void macronix_nand_onfi_init(struct nand_chip *chip)
> +{
> +	struct nand_parameters *p = &chip->parameters;
> +
> +	if (p->onfi) {
> +		struct nand_onfi_vendor_macronix *mxic =
> +				(void *)p->onfi->vendor;

Please put everything on the same line

> +
> +		if (mxic->reliability_func & MACRONIX_READ_RETRY_BIT) {
> +			chip->read_retries = MACRONIX_READ_RETRY_MODE + 1;

Why +1 here, I am missing something?

> +			chip->setup_read_retry =
> +				 macronix_nand_setup_read_retry;
> +			if (p->supports_set_get_features) {
> +				set_bit(ONFI_FEATURE_ADDR_READ_RETRY,
> +					p->set_feature_list);
> +				set_bit(ONFI_FEATURE_ADDR_READ_RETRY,
> +					p->get_feature_list);

Please use bitmap_set()

> +			}
> +		}
> +	}
> +}
> +
>  /*
>   * Macronix AC series does not support using SET/GET_FEATURES to change
>   * the timings unlike what is declared in the parameter page. Unflag
> @@ -65,6 +116,7 @@ static int macronix_nand_init(struct nand_chip *chip)
>  		chip->bbt_options |= NAND_BBT_SCAN2NDPAGE;
>  
>  	macronix_nand_fix_broken_get_timings(chip);
> +	macronix_nand_onfi_init(chip);
>  
>  	return 0;
>  }


Thanks,
Miquèl