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

Pratyush Yadav
2021-05-03T08:48:08Z

On 30/04/21 06:51PM, Boris Brezillon wrote:
> 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.

Please do not discriminate against 8D-8D-8D flashes ;-)

>
> > + 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

I don't think a separate function is needed for checking if the poll
status op is supported. Return value of -EOPNOTSUPP should be able to
signal that. This can also be used to check if Octal DDR capable
controllers are able to poll using 2-byte reads.

> 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);
> >

--
Regards,
Pratyush Yadav
Texas Instruments Inc.