linux-kernel - Re: [PATCH v3 2/9] mtd: rawnand: denali: refactor syndrome layout handling for raw access

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Date:   Tue, 12 Mar 2019 11:28:11 +0100
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     linux-mtd@...ts.infradead.org,
        Boris Brezillon <bbrezillon@...nel.org>,
        Brian Norris <computersforpeace@...il.com>,
        linux-kernel@...r.kernel.org, Marek Vasut <marek.vasut@...il.com>,
        Richard Weinberger <richard@....at>,
        David Woodhouse <dwmw2@...radead.org>
Subject: Re: [PATCH v3 2/9] mtd: rawnand: denali: refactor syndrome layout
 handling for raw access

Hi Masahiro,

Masahiro Yamada <yamada.masahiro@...ionext.com> wrote on Tue, 12 Mar
2019 17:44:43 +0900:

> The Denali IP adopts the syndrome page layout (payload and ECC are
> interleaved). The *_page_raw() and *_oob() callbacks are complicated
> because they must hide the underlying layout used by the hardware,
> and always return contiguous in-band and out-of-band data.
> 
> Currently, similar code is duplicated to reorganize the data layout.
> For example, denali_read_page_raw() and denali_write_page_raw() look
> almost the same.
> 
> The idea for refactoring is to split the code into two parts:
>   [1] conversion of page layout
>   [2] what to do at every ECC chunk boundary
> 
> For [1], I wrote denali_raw_payload_op() and denali_raw_oob_op().
> They manipulate data for the Denali controller's specific page layout
> of in-band, out-of-band, respectively.
> 
> The difference between write and read is just the operation at
> ECC chunk boundaries. For example, denali_read_oob() calls
> nand_change_read_column_op(), whereas denali_write_oob() calls
> nand_change_write_column_op(). So, I implemented [2] as a callback
> passed into [1].
> 
> Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
> ---
> 

[...]

>  static int denali_read_page_raw(struct nand_chip *chip, uint8_t *buf,
>  				int oob_required, int page)
>  {
> +	struct denali_nand_info *denali = to_denali(chip);
>  	struct mtd_info *mtd = nand_to_mtd(chip);
> -	struct denali_nand_info *denali = mtd_to_denali(mtd);
> -	int writesize = mtd->writesize;
> -	int oobsize = mtd->oobsize;
> -	int ecc_steps = chip->ecc.steps;
> -	int ecc_size = chip->ecc.size;
> -	int ecc_bytes = chip->ecc.bytes;
>  	void *tmp_buf = denali->buf;
> -	int oob_skip = denali->oob_skip_bytes;
> -	size_t size = writesize + oobsize;
> -	int ret, i, pos, len;
> +	size_t size = mtd->writesize + mtd->oobsize;
> +	int ret;
> +
> +	if (!buf)
> +		return -EINVAL;
>  
>  	ret = denali_data_xfer(chip, tmp_buf, size, page, 1, 0);
>  	if (ret)
>  		return ret;
>  
> -	/* Arrange the buffer for syndrome payload/ecc layout */
> -	if (buf) {
> -		for (i = 0; i < ecc_steps; i++) {
> -			pos = i * (ecc_size + ecc_bytes);
> -			len = ecc_size;
> -
> -			if (pos >= writesize)
> -				pos += oob_skip;
> -			else if (pos + len > writesize)
> -				len = writesize - pos;
> -
> -			memcpy(buf, tmp_buf + pos, len);
> -			buf += len;
> -			if (len < ecc_size) {
> -				len = ecc_size - len;
> -				memcpy(buf, tmp_buf + writesize + oob_skip,
> -				       len);
> -				buf += len;
> -			}
> -		}
> -	}
> +	ret = denali_raw_payload_op(chip, buf, denali_memcpy_in, tmp_buf);

Honestly, I still don't like passing denali_memcpy_in/out as parameter.

Besides that, once you'll have added helpers to avoid abusing the
ternary operator in 4/9, the rest looks fine by me.

Thanks,
Miquèl