[PATCH v2] spi: cadence_qspi: Fix odd byte write issue in STIG mode

[Prasanth Mantena]

On 13:51, Prasanth Mantena wrote:
> On 09:34, Venkatesh Yadav Abbarapu wrote:
> > Starting from 'commit <8077d296adff> ("spi: cadence-quadspi: Use STIG
> > mode for all ops with small payload") the utilization of STIG mode
> > has been implemented for read and write operations involving less
> > than 8 bytes of data.
> > 
> > However, following this commit, encountering timeout issues occurs when
> > writing odd bytes of data in DDR mode, as indicated below:
> > "jedec_spi_nor flash at 0: flash operation timed out
> > SF: 3 bytes @ 0x0 Written: ERROR -110"
> > 
> > To resolve this issue, the number of bytes to write has been updated
> > specifically for DDR mode.
> > 
> > Signed-off-by: Tejas Bhumkar <tejas.arvind.bhumkar at amd.com>
> > Signed-off-by: Venkatesh Yadav Abbarapu <venkatesh.abbarapu at amd.com>
> > ---
> > Changes in v2:
> > -Modified the logic from using modulus and changed to use "logical and" 
> > operator to check the odd bytes.
> > ---
> >  drivers/spi/cadence_qspi_apb.c | 3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > diff --git a/drivers/spi/cadence_qspi_apb.c b/drivers/spi/cadence_qspi_apb.c
> > index b579699d2eb..76569a8019b 100644
> > --- a/drivers/spi/cadence_qspi_apb.c
> > +++ b/drivers/spi/cadence_qspi_apb.c
> > @@ -554,6 +554,9 @@ int cadence_qspi_apb_command_write(struct cadence_spi_priv *priv,
> >  	void *reg_base = priv->regbase;
> >  	u8 opcode;
> >  
> > +	if (priv->dtr)
> > +		txlen += txlen & 1;
> > +
> 
> Hi Venkatesh,
> 
> 1> Is this not a generic problem, having a DTR write in stig mode. If so,
> shouldn't this be handled at the spi-nor core level.
> 
> 2> You are just increasing the number of bytes here, aren't we writing
> an unwanted extra data ? Where did we pad the buffer ?
>

NACK. Considering the issues that this can cause, referring the above comments.
Michal Simek, my request is to please wait for some comment / review for
the common code like this, considering this merge was quick.

Thanks,
Prasanth
 
> 
> Thanks,
> Prasanth
> 
> >  	if (priv->dtr)
> >  		opcode = op->cmd.opcode >> 8;
> >  	else
> > -- 
> > 2.34.1
> >