Re: [PATCH v3 2/3] mtd: spinand: use the spi-mem poll status APIs

Boris Brezillon
2021-05-18T11:29:02Z

On Tue, 18 May 2021 11:39:50 +0200
<patrice.chotard@foss.st.com> wrote:

> From: Patrice Chotard <patrice.chotard@foss.st.com>
>
> Make use of spi-mem poll status APIs to let advanced controllers
> optimize wait operations.

This should also fix the high CPU usage you were reporting for those
that don't have a dedicated STATUS poll block logic, which is great!

>
> Signed-off-by: Patrice Chotard <patrice.chotard@foss.st.com>
> Signed-off-by: Christophe Kerello <christophe.kerello@foss.st.com>
> ---
> Changes in v3:
> - Add initial_delay_us and polling_delay_us parameters to spinand_wait()
> - Add SPINAND_READ/WRITE/ERASE/RESET_INITIAL_DELAY_US and
> SPINAND_READ/WRITE/ERASE/RESET_POLL_DELAY_US defines.
>
> Changes in v2:
> - non-offload case is now managed by spi_mem_poll_status()
>
> drivers/mtd/nand/spi/core.c | 45 ++++++++++++++++++++++++++-----------
> include/linux/mtd/spinand.h | 11 ++++++++-
> 2 files changed, 42 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/mtd/nand/spi/core.c b/drivers/mtd/nand/spi/core.c
> index 17f63f95f4a2..ef2a692ab5b6 100644
> --- a/drivers/mtd/nand/spi/core.c
> +++ b/drivers/mtd/nand/spi/core.c
> @@ -473,20 +473,26 @@ static int spinand_erase_op(struct spinand_device *spinand,
> return spi_mem_exec_op(spinand->spimem, &op);
> }
>
> -static int spinand_wait(struct spinand_device *spinand, u8 *s)
> +static int spinand_wait(struct spinand_device *spinand,
> + unsigned long initial_delay_us,
> + unsigned long poll_delay_us,
> + u8 *s)
> {
> - unsigned long timeo = jiffies + msecs_to_jiffies(400);
> + struct spi_mem_op op = SPINAND_GET_FEATURE_OP(REG_STATUS,
> + spinand->scratchbuf);
> u8 status;
> int ret;
>
> - do {
> - ret = spinand_read_status(spinand, &status);
> - if (ret)
> - return ret;
> + ret = spi_mem_poll_status(spinand->spimem, &op, STATUS_BUSY, 0,
> + initial_delay_us,
> + poll_delay_us,
> + SPINAND_STATUS_TIMEOUT_MS);
> + if (ret)
> + return ret;
>
> - if (!(status & STATUS_BUSY))
> - goto out;
> - } while (time_before(jiffies, timeo));
> + status = *spinand->scratchbuf;
> + if (!(status & STATUS_BUSY))
> + goto out;
>
> /*
> * Extra read, just in case the STATUS_READY bit has changed
> @@ -526,7 +532,10 @@ static int spinand_reset_op(struct spinand_device *spinand)
> if (ret)
> return ret;
>
> - return spinand_wait(spinand, NULL);
> + return spinand_wait(spinand,
> + SPINAND_RESET_INITIAL_DELAY_US,
> + SPINAND_RESET_POLL_DELAY_US,
> + NULL);
> }
>
> static int spinand_lock_block(struct spinand_device *spinand, u8 lock)
> @@ -549,7 +558,10 @@ static int spinand_read_page(struct spinand_device *spinand,
> if (ret)
> return ret;
>
> - ret = spinand_wait(spinand, &status);
> + ret = spinand_wait(spinand,
> + SPINAND_READ_INITIAL_DELAY_US,
> + SPINAND_READ_POLL_DELAY_US,
> + &status);
> if (ret < 0)
> return ret;
>
> @@ -585,7 +597,10 @@ static int spinand_write_page(struct spinand_device *spinand,
> if (ret)
> return ret;
>
> - ret = spinand_wait(spinand, &status);
> + ret = spinand_wait(spinand,
> + SPINAND_WRITE_INITIAL_DELAY_US,
> + SPINAND_WRITE_POLL_DELAY_US,
> + &status);
> if (!ret && (status & STATUS_PROG_FAILED))
> return -EIO;
>
> @@ -768,7 +783,11 @@ static int spinand_erase(struct nand_device *nand, const struct nand_pos *pos)
> if (ret)
> return ret;
>
> - ret = spinand_wait(spinand, &status);
> + ret = spinand_wait(spinand,
> + SPINAND_ERASE_INITIAL_DELAY_US,
> + SPINAND_ERASE_POLL_DELAY_US,
> + &status);
> +
> if (!ret && (status & STATUS_ERASE_FAILED))
> ret = -EIO;
>
> diff --git a/include/linux/mtd/spinand.h b/include/linux/mtd/spinand.h
> index 6bb92f26833e..180c1fa64e62 100644
> --- a/include/linux/mtd/spinand.h
> +++ b/include/linux/mtd/spinand.h
> @@ -169,7 +169,16 @@
> struct spinand_op;
> struct spinand_device;
>
> -#define SPINAND_MAX_ID_LEN 4
> +#define SPINAND_MAX_ID_LEN 4
> +#define SPINAND_READ_INITIAL_DELAY_US 6
> +#define SPINAND_READ_POLL_DELAY_US 5
> +#define SPINAND_RESET_INITIAL_DELAY_US 5
> +#define SPINAND_RESET_POLL_DELAY_US 5
> +#define SPINAND_WRITE_INITIAL_DELAY_US 75
> +#define SPINAND_WRITE_POLL_DELAY_US 15
> +#define SPINAND_ERASE_INITIAL_DELAY_US 250
> +#define SPINAND_ERASE_POLL_DELAY_US 50

Could you add a comment explaining where those numbers come from?

> +#define SPINAND_STATUS_TIMEOUT_MS 400

I would name that one SPINAND_WAITRDY_TIMEOUT_MS.

>
> /**
> * struct spinand_id - SPI NAND id structure