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 11:54:25 +0100
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     Boris Brezillon <bbrezillon@...nel.org>,
        Richard Weinberger <richard@....at>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Marek Vasut <marek.vasut@...il.com>,
        linux-mtd <linux-mtd@...ts.infradead.org>,
        Brian Norris <computersforpeace@...il.com>,
        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 19:51:21 +0900:

> On Tue, Mar 12, 2019 at 7:28 PM Miquel Raynal <miquel.raynal@...tlin.com> wrote:
> >
> > 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.
> >  
> 
> 
> Do you have any suggestion?

Maybe register these two helpers at probe as controller specific hooks,
then just pass an in/out boolean to the function?

Thanks,
Miquèl