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

[Pratyush Yadav <p.yadav@xxxxxx>]

On 30/04/21 06:51PM, Boris Brezillon wrote:
> On Mon, 26 Apr 2021 16:39:32 +0200
> <patrice.chotard@xxxxxxxxxxx> wrote:
> 
> > From: Christophe Kerello <christophe.kerello@xxxxxxxxxxx>
> > 
> > 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@xxxxxxxxxxx>
> > Signed-off-by: Patrice Chotard <patrice.chotard@xxxxxxxxxxx>
> > ---
> >  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.