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    SubjectRe: [RFC PATCH 4/8] mtd: rawnand: ams-delta: Optimize pointer resolution on read/write
    On Thu, 19 Jul 2018 01:57:06 +0200
    Janusz Krzysztofik <jmkrzyszt@gmail.com> wrote:

    > Further optimize processing speed of read/write callback functions by
    > resolving private structure pointer only once per callback and passing
    > it to all subfunctions instead of mtd_info.

    Not sure this has a real impact on perfs, but I also prefer not using
    mtd_info objects within NAND drivers, so I'm good with the change
    itself (its probably worth changing the commit message though)

    >
    > Signed-off-by: Janusz Krzysztofik <jmkrzyszt@gmail.com>
    > ---
    > drivers/mtd/nand/raw/ams-delta.c | 44 +++++++++++++++++++++++-----------------
    > 1 file changed, 25 insertions(+), 19 deletions(-)
    >
    > diff --git a/drivers/mtd/nand/raw/ams-delta.c b/drivers/mtd/nand/raw/ams-delta.c
    > index dfefcd79b420..d7e4c9dbef67 100644
    > --- a/drivers/mtd/nand/raw/ams-delta.c
    > +++ b/drivers/mtd/nand/raw/ams-delta.c
    > @@ -72,10 +72,9 @@ static const struct mtd_partition partition_info[] = {
    > .size = 3 * SZ_256K },
    > };
    >
    > -static void ams_delta_write_next_byte(struct mtd_info *mtd, u_char byte)
    > +static void ams_delta_write_next_byte(struct ams_delta_nand *priv, u_char byte)
    > {
    > - struct nand_chip *this = mtd_to_nand(mtd);
    > - struct ams_delta_nand *priv = nand_get_controller_data(this);
    > + struct nand_chip *this = &priv->nand_chip;
    >
    > writew(byte, this->IO_ADDR_W);
    > gpiod_set_value(priv->gpiod_nwe, 0);
    > @@ -83,21 +82,18 @@ static void ams_delta_write_next_byte(struct mtd_info *mtd, u_char byte)
    > gpiod_set_value(priv->gpiod_nwe, 1);
    > }
    >
    > -static void ams_delta_write_byte(struct mtd_info *mtd, u_char byte)
    > +static void ams_delta_write_first_byte(struct ams_delta_nand *priv, u_char byte)
    > {
    > - struct nand_chip *this = mtd_to_nand(mtd);
    > - struct ams_delta_nand *priv = nand_get_controller_data(this);
    > void __iomem *io_base = priv->io_base;
    >
    > writew(0, io_base + OMAP_MPUIO_IO_CNTL);
    >
    > - ams_delta_write_next_byte(mtd, byte);
    > + ams_delta_write_next_byte(priv, byte);
    > }
    >
    > -static u_char ams_delta_read_next_byte(struct mtd_info *mtd)
    > +static u_char ams_delta_read_next_byte(struct ams_delta_nand *priv)
    > {
    > - struct nand_chip *this = mtd_to_nand(mtd);
    > - struct ams_delta_nand *priv = nand_get_controller_data(this);
    > + struct nand_chip *this = &priv->nand_chip;
    > u_char res;
    >
    > gpiod_set_value(priv->gpiod_nre, 0);
    > @@ -108,36 +104,46 @@ static u_char ams_delta_read_next_byte(struct mtd_info *mtd)
    > return res;
    > }
    >
    > -static u_char ams_delta_read_byte(struct mtd_info *mtd)
    > +static u_char ams_delta_read_first_byte(struct ams_delta_nand *priv)
    > {
    > - struct nand_chip *this = mtd_to_nand(mtd);
    > - struct ams_delta_nand *priv = nand_get_controller_data(this);
    > void __iomem *io_base = priv->io_base;
    >
    > writew(~0, io_base + OMAP_MPUIO_IO_CNTL);
    >
    > - return ams_delta_read_next_byte(mtd);
    > + return ams_delta_read_next_byte(priv);
    > +}
    > +
    > +static u_char ams_delta_read_byte(struct mtd_info *mtd)
    > +{
    > + struct nand_chip *this = mtd_to_nand(mtd);
    > + struct ams_delta_nand *priv = nand_get_controller_data(this);
    > +
    > + return ams_delta_read_first_byte(priv);
    > }
    >
    > static void ams_delta_write_buf(struct mtd_info *mtd, const u_char *buf,
    > int len)
    > {
    > + struct nand_chip *this = mtd_to_nand(mtd);
    > + struct ams_delta_nand *priv = nand_get_controller_data(this);
    > int i;
    >
    > if (len > 0)
    > - ams_delta_write_byte(mtd, buf[0]);
    > + ams_delta_write_first_byte(priv, buf[0]);
    > for (i = 1; i < len; i++)
    > - ams_delta_write_next_byte(mtd, buf[i]);
    > + ams_delta_write_next_byte(priv, buf[i]);
    > }
    >
    > static void ams_delta_read_buf(struct mtd_info *mtd, u_char *buf, int len)
    > {
    > + struct nand_chip *this = mtd_to_nand(mtd);
    > + struct ams_delta_nand *priv = nand_get_controller_data(this);
    > int i;
    >
    > if (len > 0)
    > - buf[0] = ams_delta_read_byte(mtd);
    > + buf[0] = ams_delta_read_first_byte(priv);
    > for (i = 1; i < len; i++)
    > - buf[i] = ams_delta_read_next_byte(mtd);
    > + buf[i] = ams_delta_read_next_byte(priv);
    > }
    >
    > /*
    > @@ -161,7 +167,7 @@ static void ams_delta_hwcontrol(struct mtd_info *mtd, int cmd,
    > }
    >
    > if (cmd != NAND_CMD_NONE)
    > - ams_delta_write_byte(mtd, cmd);
    > + ams_delta_write_first_byte(priv, cmd);
    > }
    >
    > static int ams_delta_nand_ready(struct mtd_info *mtd)

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