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SubjectRe: [PATCH v4 3/3] mtd: rawnand: ams-delta: Set port direction when needed
On Mon, 20 Aug 2018 23:39:04 +0200
Janusz Krzysztofik <jmkrzyszt@gmail.com> wrote:

> In its current shape, the driver sets data port direction before each
> byte read/write operation, even during multi-byte transfers. Improve
> performance of the driver by setting the port direction only when
> needed.
>
> This optimisation will become particularly important as soon as
> planned conversion of the driver to GPIO API for data I/O will be
> implemented.
>
> Signed-off-by: Janusz Krzysztofik <jmkrzyszt@gmail.com>

Reviewed-by: Boris Brezillon <boris.brezillon@bootlin.com>

> ---
> drivers/mtd/nand/raw/ams-delta.c | 68 ++++++++++++++++++++++++++--------------
> 1 file changed, 45 insertions(+), 23 deletions(-)
>
> diff --git a/drivers/mtd/nand/raw/ams-delta.c b/drivers/mtd/nand/raw/ams-delta.c
> index 48233d638d2a..4d5e5790f18e 100644
> --- a/drivers/mtd/nand/raw/ams-delta.c
> +++ b/drivers/mtd/nand/raw/ams-delta.c
> @@ -45,6 +45,7 @@ struct ams_delta_nand {
> struct gpio_desc *gpiod_ale;
> struct gpio_desc *gpiod_cle;
> void __iomem *io_base;
> + bool data_in;
> };
>
> /*
> @@ -72,50 +73,65 @@ static const struct mtd_partition partition_info[] = {
> .size = 3 * SZ_256K },
> };
>
> -static void ams_delta_write_byte(struct mtd_info *mtd, u_char byte)
> +static void ams_delta_io_write(struct ams_delta_nand *priv, u8 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);
> - writew(byte, this->IO_ADDR_W);
> + writew(byte, priv->nand_chip.IO_ADDR_W);
> gpiod_set_value(priv->gpiod_nwe, 0);
> ndelay(40);
> gpiod_set_value(priv->gpiod_nwe, 1);
> }
>
> -static u_char ams_delta_read_byte(struct mtd_info *mtd)
> +static u8 ams_delta_io_read(struct ams_delta_nand *priv)
> {
> - u_char res;
> - 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;
> + u8 res;
>
> gpiod_set_value(priv->gpiod_nre, 0);
> ndelay(40);
> - writew(~0, io_base + OMAP_MPUIO_IO_CNTL);
> - res = readw(this->IO_ADDR_R);
> + res = readw(priv->nand_chip.IO_ADDR_R);
> gpiod_set_value(priv->gpiod_nre, 1);
>
> return res;
> }
>
> -static void ams_delta_write_buf(struct mtd_info *mtd, const u_char *buf,
> - int len)
> +static void ams_delta_dir_input(struct ams_delta_nand *priv, bool in)
> {
> + writew(in ? ~0 : 0, priv->io_base + OMAP_MPUIO_IO_CNTL);
> + priv->data_in = in;
> +}
> +
> +static void ams_delta_write_buf(struct mtd_info *mtd, const u8 *buf, int len)
> +{
> + struct nand_chip *this = mtd_to_nand(mtd);
> + struct ams_delta_nand *priv = nand_get_controller_data(this);
> int i;
>
> - for (i=0; i<len; i++)
> - ams_delta_write_byte(mtd, buf[i]);
> + if (priv->data_in)
> + ams_delta_dir_input(priv, false);
> +
> + for (i = 0; i < len; i++)
> + ams_delta_io_write(priv, buf[i]);
> }
>
> -static void ams_delta_read_buf(struct mtd_info *mtd, u_char *buf, int len)
> +static void ams_delta_read_buf(struct mtd_info *mtd, u8 *buf, int len)
> {
> + struct nand_chip *this = mtd_to_nand(mtd);
> + struct ams_delta_nand *priv = nand_get_controller_data(this);
> int i;
>
> - for (i=0; i<len; i++)
> - buf[i] = ams_delta_read_byte(mtd);
> + if (!priv->data_in)
> + ams_delta_dir_input(priv, true);
> +
> + for (i = 0; i < len; i++)
> + buf[i] = ams_delta_io_read(priv);
> +}
> +
> +static u8 ams_delta_read_byte(struct mtd_info *mtd)
> +{
> + u8 res;
> +
> + ams_delta_read_buf(mtd, &res, 1);
> +
> + return res;
> }
>
> /*
> @@ -138,8 +154,11 @@ static void ams_delta_hwcontrol(struct mtd_info *mtd, int cmd,
> gpiod_set_value(priv->gpiod_ale, !!(ctrl & NAND_ALE));
> }
>
> - if (cmd != NAND_CMD_NONE)
> - ams_delta_write_byte(mtd, cmd);
> + if (cmd != NAND_CMD_NONE) {
> + u8 byte = cmd;
> +
> + ams_delta_write_buf(mtd, &byte, 1);
> + }
> }
>
> static int ams_delta_nand_ready(struct mtd_info *mtd)
> @@ -262,6 +281,9 @@ static int ams_delta_init(struct platform_device *pdev)
> goto out_mtd;
> }
>
> + /* Initialize data port direction to a known state */
> + ams_delta_dir_input(priv, true);
> +
> /* Scan to find existence of the device */
> err = nand_scan(mtd, 1);
> if (err)

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