linux-kernel - Re: [PATCH v4 1/3] spi: spi-mem: add automatic poll status functions

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Message-ID: <20210518161252.3e4f2999@collabora.com>
Date:   Tue, 18 May 2021 16:12:52 +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 1/3] spi: spi-mem: add automatic poll status
 functions

On Tue, 18 May 2021 15:43:30 +0200
<patrice.chotard@...s.st.com> wrote:

> From: Patrice Chotard <patrice.chotard@...s.st.com>
> 
> With STM32 QSPI, it is possible to poll the status register of the device.
> This could be done to offload the CPU during an operation (erase or
> program a SPI NAND for example).
> 
> spi_mem_poll_status API has been added to handle this feature.
> This new function take care of the offload/non-offload cases.
> 
> For the non-offload case, use read_poll_timeout() to poll the status in
> order to release CPU during this phase.
> For example, previously, when erasing large area, in non-offload case,
> CPU load can reach ~50%, now it decrease to ~35%.
> 
> Signed-off-by: Patrice Chotard <patrice.chotard@...s.st.com>
> Signed-off-by: Christophe Kerello <christophe.kerello@...s.st.com>
> ---
> Changes in v4:
>   - Remove init_completion() from spi_mem_probe() added in v2.
>   - Add missing static for spi_mem_read_status().
>   - Check if operation in spi_mem_poll_status() is a READ.
> 
> Changes in v3:
>   - Add spi_mem_read_status() which allows to read 8 or 16 bits status.
>   - Add initial_delay_us and polling_delay_us parameters to spi_mem_poll_status()
>     and also to poll_status() callback.
>   - Move spi_mem_supports_op() in SW-based polling case.
>   - Add delay before invoking read_poll_timeout().
>   - Remove the reinit/wait_for_completion() added in v2.
> 
> Changes in v2:
>   - Indicates the spi_mem_poll_status() timeout unit
>   - Use 2-byte wide status register
>   - Add spi_mem_supports_op() call in spi_mem_poll_status()
>   - Add completion management in spi_mem_poll_status()
>   - Add offload/non-offload case management in spi_mem_poll_status()
>   - Optimize the non-offload case by using read_poll_timeout()
> 
>  drivers/spi/spi-mem.c       | 85 +++++++++++++++++++++++++++++++++++++
>  include/linux/spi/spi-mem.h | 14 ++++++
>  2 files changed, 99 insertions(+)
> 
> diff --git a/drivers/spi/spi-mem.c b/drivers/spi/spi-mem.c
> index 1513553e4080..97c7a83686c7 100644
> --- a/drivers/spi/spi-mem.c
> +++ b/drivers/spi/spi-mem.c
> @@ -6,6 +6,7 @@
>   * Author: Boris Brezillon <boris.brezillon@...tlin.com>
>   */
>  #include <linux/dmaengine.h>
> +#include <linux/iopoll.h>
>  #include <linux/pm_runtime.h>
>  #include <linux/spi/spi.h>
>  #include <linux/spi/spi-mem.h>
> @@ -743,6 +744,90 @@ static inline struct spi_mem_driver *to_spi_mem_drv(struct device_driver *drv)
>  	return container_of(drv, struct spi_mem_driver, spidrv.driver);
>  }
>  
> +static int spi_mem_read_status(struct spi_mem *mem,
> +			       const struct spi_mem_op *op,
> +			       u16 *status)
> +{
> +	const u8 *bytes = (u8 *)op->data.buf.in;
> +	int ret;
> +
> +	ret = spi_mem_exec_op(mem, op);
> +	if (ret)
> +		return ret;
> +
> +	if (op->data.nbytes > 1)
> +		*status = ((u16)bytes[0] << 8) | bytes[1];
> +	else
> +		*status = bytes[0];
> +
> +	return 0;
> +}
> +
> +/**
> + * spi_mem_poll_status() - Poll memory device status
> + * @mem: SPI memory device
> + * @op: the memory operation to execute
> + * @mask: status bitmask to ckeck
> + * @match: (status & mask) expected value
> + * @initial_delay_us: delay in us before starting to poll
> + * @polling_delay_us: time to sleep between reads in us
> + * @timeout_ms: timeout in milliseconds
> + *
> + * This function send a polling status request to the controller driver

"
This function polls a status register and returns when
(status & mask) == match or when the timeout has expired.
"

> + *
> + * Return: 0 in case of success, -ETIMEDOUT in case of error,
> + *         -EOPNOTSUPP if not supported.
> + */
> +int spi_mem_poll_status(struct spi_mem *mem,
> +			const struct spi_mem_op *op,
> +			u16 mask, u16 match,
> +			unsigned long initial_delay_us,
> +			unsigned long polling_delay_us,
> +			u16 timeout_ms)
> +{
> +	struct spi_controller *ctlr = mem->spi->controller;
> +	int ret = -EOPNOTSUPP;
> +	int read_status_ret;
> +	u16 status;
> +
> +	if (op->data.nbytes < 1 || op->data.nbytes > 2 ||
> +	    op->data.dir != SPI_MEM_DATA_IN)
> +		return (-EINVAL);

s/return (-EINVAL);/return -EINVAL;/


[...]

>  /**
> @@ -369,6 +376,13 @@ devm_spi_mem_dirmap_create(struct device *dev, struct spi_mem *mem,
>  void devm_spi_mem_dirmap_destroy(struct device *dev,
>  				 struct spi_mem_dirmap_desc *desc);
>  
> +int spi_mem_poll_status(struct spi_mem *mem,
> +			const struct spi_mem_op *op,
> +			u16 mask, u16 match,
> +			unsigned long initial_delay_us,
> +			unsigned long polling_delay_us,
> +			u16 timeout);

s/timeout/timeout_ms/.

With those minor things fixed

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

> +
>  int spi_mem_driver_register_with_owner(struct spi_mem_driver *drv,
>  				       struct module *owner);
>