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

[Patrice CHOTARD <patrice.chotard@foss.st.com>]

Hi Pratyush

On 4/26/21 6:26 PM, Pratyush Yadav wrote:
> Hi,
> 
> On 26/04/21 04:39PM, 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
> 
> Technically, (status & mask) expected value. Dunno if that is obvious 
> enough to not spell out explicitly.

Yes, match = (status & mask)
I will update the comment accordingly.

> 
>> + * @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) {
> 
> You should call spi_mem_supports_op() before sending any ops to the 
> controller. Invalid/unsupported ops can cause unexpected behavior.

Ok i will add it.

Thanks
Patrice

> 
>> +		ret = spi_mem_access_start(mem);
>> +		if (ret)
>> +			return ret;
>> +
>> +		ret = ctlr->mem_ops->poll_status(mem, op, mask, match, timeout);
> 
> I wonder if it is better to let spi-mem core take care of the timeout 
> part. On one hand it reduces code duplication on the driver side a 
> little bit. Plus it makes sure drivers don't mess anything up with bad 
> (or no) handling of the timeout. But on the other hand the interface 
> becomes a bit awkward since you'd have to pass a struct completion 
> around, and it isn't something particularly hard to get right either. 
> What do you think?
> 
>> +
>> +		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);
>