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

Boris Brezillon
2021-04-30T16:51:25Z

On Mon, 26 Apr 2021 16:39:32 +0200
<patrice.chotard@foss.st.com> wrote:

> From: Christophe Kerello <christophe.kerello@foss.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.
>
> Signed-off-by: Christophe Kerello <christophe.kerello@foss.st.com>
> Signed-off-by: Patrice Chotard <patrice.chotard@foss.st.com>
> ---
> drivers/spi/spi-mem.c | 34 ++++++++++++++++++++++++++++++++++
> include/linux/spi/spi-mem.h | 8 ++++++++
> 2 files changed, 42 insertions(+)
>
> diff --git a/drivers/spi/spi-mem.c b/drivers/spi/spi-mem.c
> index 1513553e4080..43dce4b0efa4 100644
> --- a/drivers/spi/spi-mem.c
> +++ b/drivers/spi/spi-mem.c
> @@ -743,6 +743,40 @@ static inline struct spi_mem_driver *to_spi_mem_drv(struct device_driver *drv)
> return container_of(drv, struct spi_mem_driver, spidrv.driver);
> }
>
> +/**
> + * 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 expected value
> + * @timeout: timeout
> + *
> + * This function send a polling status request to the controller driver
> + *
> + * 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,
> + u8 mask, u8 match, u16 timeout)
> +{
> + struct spi_controller *ctlr = mem->spi->controller;
> + int ret = -EOPNOTSUPP;
> +
> + if (ctlr->mem_ops && ctlr->mem_ops->poll_status) {
> + ret = spi_mem_access_start(mem);

You should probably check that op is a single byte read before
accepting the command.

> + if (ret)
> + return ret;
> +
> + ret = ctlr->mem_ops->poll_status(mem, op, mask, match, timeout);

You also need some sort of ->poll_status_is_supported() to validate
that the controller supports the status polling for this specific op (I
can imagine some controllers having a limit on the number of dummy
cycles/address bytes). I guess you could just fall back on SW-based
status polling if ctlr->mem_ops->poll_status() returns -ENOTSUPP.

> +
> + spi_mem_access_end(mem);
> + }
> +
> + return ret;
> +}
> +EXPORT_SYMBOL_GPL(spi_mem_poll_status);
> +
> static int spi_mem_probe(struct spi_device *spi)
> {
> struct spi_mem_driver *memdrv = to_spi_mem_drv(spi->dev.driver);
> diff --git a/include/linux/spi/spi-mem.h b/include/linux/spi/spi-mem.h
> index 2b65c9edc34e..5f78917c0f68 100644
> --- a/include/linux/spi/spi-mem.h
> +++ b/include/linux/spi/spi-mem.h
> @@ -250,6 +250,7 @@ static inline void *spi_mem_get_drvdata(struct spi_mem *mem)
> * the currently mapped area), and the caller of
> * spi_mem_dirmap_write() is responsible for calling it again in
> * this case.
> + * @poll_status: poll memory device status
> *
> * This interface should be implemented by SPI controllers providing an
> * high-level interface to execute SPI memory operation, which is usually the
> @@ -274,6 +275,9 @@ struct spi_controller_mem_ops {
> u64 offs, size_t len, void *buf);
> ssize_t (*dirmap_write)(struct spi_mem_dirmap_desc *desc,
> u64 offs, size_t len, const void *buf);
> + int (*poll_status)(struct spi_mem *mem,
> + const struct spi_mem_op *op,
> + u8 mask, u8 match, u16 timeout);
> };
>
> /**
> @@ -369,6 +373,10 @@ 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,
> + u8 mask, u8 match, u16 timeout);
> +
> int spi_mem_driver_register_with_owner(struct spi_mem_driver *drv,
> struct module *owner);
>