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Message-ID: <20210518161834.6860c310@collabora.com>
Date: Tue, 18 May 2021 16:18:34 +0200
From: Boris Brezillon <boris.brezillon@...labora.com>
To: <patrice.chotard@...s.st.com>
Cc: Mark Brown <broonie@...nel.org>,
Miquel Raynal <miquel.raynal@...tlin.com>,
Vignesh Raghavendra <vigneshr@...com>,
<linux-mtd@...ts.infradead.org>,
Alexandre Torgue <alexandre.torgue@...s.st.com>,
<linux-spi@...r.kernel.org>,
<linux-stm32@...md-mailman.stormreply.com>,
<linux-arm-kernel@...ts.infradead.org>,
<linux-kernel@...r.kernel.org>, <christophe.kerello@...s.st.com>
Subject: Re: [PATCH v4 2/3] mtd: spinand: use the spi-mem poll status APIs
On Tue, 18 May 2021 15:43:31 +0200
<patrice.chotard@...s.st.com> wrote:
> From: Patrice Chotard <patrice.chotard@...s.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 for system that don't have
> a dedicated STATUS poll block logic.
>
> Signed-off-by: Patrice Chotard <patrice.chotard@...s.st.com>
> Signed-off-by: Christophe Kerello <christophe.kerello@...s.st.com>
> ---
> Changes in v4:
> - Update commit message.
> - Add comment which explains how delays has been calculated.
> - Rename SPINAND_STATUS_TIMEOUT_MS to SPINAND_WAITRDY_TIMEOUT_MS.
>
> 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 | 22 ++++++++++++++++++
> 2 files changed, 54 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/mtd/nand/spi/core.c b/drivers/mtd/nand/spi/core.c
> index 17f63f95f4a2..3131fae0c715 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_WAITRDY_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;
Looks like you expect the driver to not only wait for a status change
but also fill the data buffer with the last status value. I think that
should be documented in the SPI mem API.
> /*
> * 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..6988956b8492 100644
> --- a/include/linux/mtd/spinand.h
> +++ b/include/linux/mtd/spinand.h
> @@ -170,6 +170,28 @@ struct spinand_op;
> struct spinand_device;
>
> #define SPINAND_MAX_ID_LEN 4
> +/*
> + * For erase, write and read operation, we got the following timings :
> + * tBERS (erase) 1ms to 4ms
> + * tPROG 300us to 400us
> + * tREAD 25us to 100us
> + * In order to minimize latency, the min value is divided by 4 for the
> + * initial delay, and dividing by 20 for the poll delay.
> + * For reset, 5us/10us/500us if the device is respectively
> + * reading/programming/erasing when the RESET occurs. Since we always
> + * issue a RESET when the device is IDLE, 5us is selected for both initial
> + * and poll delay.
> + */
> +#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
> +
> +#define SPINAND_WAITRDY_TIMEOUT_MS 400
>
> /**
> * struct spinand_id - SPI NAND id structure
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