Re: [PATCH v3 3/6] spi: sun6i: restrict transfer length in PIO-mode

[Sergey Suloev]

On 04/04/2018 09:50 AM, Maxime Ripard wrote:
> On Tue, Apr 03, 2018 at 06:44:46PM +0300, Sergey Suloev wrote:
> > There is no need to handle 3/4 empty interrupt as the maximum
> > supported transfer length in PIO mode is equal to FIFO depth,
> > i.e. 128 bytes for sun6i and 64 bytes for sun8i SoCs.
> >
> > Changes in v3:
> > 1) Restored processing of 3/4 FIFO full interrupt.
> >
> > Signed-off-by: Sergey Suloev <ssuloev@xxxxxxxxxxxxx>
> > ---
> >   drivers/spi/spi-sun6i.c | 41 +++++++++++++++++------------------------
> >   1 file changed, 17 insertions(+), 24 deletions(-)
> >
> > diff --git a/drivers/spi/spi-sun6i.c b/drivers/spi/spi-sun6i.c
> > index 78acc1f..c09ad10 100644
> > --- a/drivers/spi/spi-sun6i.c
> > +++ b/drivers/spi/spi-sun6i.c
> > @@ -207,7 +207,10 @@ static void sun6i_spi_set_cs(struct spi_device *spi, bool enable)
> >   
> >   static size_t sun6i_spi_max_transfer_size(struct spi_device *spi)
> >   {
> > -	return SUN6I_MAX_XFER_SIZE - 1;
> > +	struct spi_master *master = spi->master;
> > +	struct sun6i_spi *sspi = spi_master_get_devdata(master);
> > +
> > +	return sspi->fifo_depth;
> Doesn't that effectively revert 3288d5cb40c0 ?
>
> Why do you need to do so?
Need what?

Change is supposed to restrict max transfer size for PIO mode otherwise 
it will fail.
The maximum transfer length = FIFO depth for PIO mode.

> >   }
> >   
> >   static int sun6i_spi_prepare_message(struct spi_master *master,
> > @@ -255,8 +258,14 @@ static int sun6i_spi_transfer_one(struct spi_master *master,
> >   	int ret = 0;
> >   	u32 reg;
> >   
> > -	if (tfr->len > SUN6I_MAX_XFER_SIZE)
> > -		return -EINVAL;
> > +	/* A zero length transfer never finishes if programmed
> > +	   in the hardware */
> Improper comment style here. Please make sure to run checkpatch before
> sending your patches.
ok
> > +	if (!tfr->len)
> > +		return 0;
> Can that case even happen?
Not sure, just for safety.
> > +	/* Don't support transfer larger than the FIFO */
> > +	if (tfr->len > sspi->fifo_depth)
> > +		return -EMSGSIZE;
> You're changing the return type, why?
As  a more appropriate one
> >   	reinit_completion(&sspi->done);
> >   	sspi->tx_buf = tfr->tx_buf;
> > @@ -278,8 +287,7 @@ static int sun6i_spi_transfer_one(struct spi_master *master,
> >   	 */
> >   	trig_level = sspi->fifo_depth / 4 * 3;
> >   	sun6i_spi_write(sspi, SUN6I_FIFO_CTL_REG,
> > -			(trig_level << SUN6I_FIFO_CTL_RF_RDY_TRIG_LEVEL_BITS) |
> > -			(trig_level << SUN6I_FIFO_CTL_TF_ERQ_TRIG_LEVEL_BITS));
> > +			(trig_level << SUN6I_FIFO_CTL_RF_RDY_TRIG_LEVEL_BITS));
> >   
> >   
> >   	reg = sun6i_spi_read(sspi, SUN6I_TFR_CTL_REG);
> > @@ -343,11 +351,8 @@ static int sun6i_spi_transfer_one(struct spi_master *master,
> >   	sun6i_spi_fill_fifo(sspi, sspi->fifo_depth);
> >   
> >   	/* Enable the interrupts */
> > -	sun6i_spi_write(sspi, SUN6I_INT_CTL_REG, SUN6I_INT_CTL_TC);
> >   	sun6i_spi_enable_interrupt(sspi, SUN6I_INT_CTL_TC |
> >   					 SUN6I_INT_CTL_RF_RDY);
> > -	if (tx_len > sspi->fifo_depth)
> > -		sun6i_spi_enable_interrupt(sspi, SUN6I_INT_CTL_TF_ERQ);
> This would also need to be explained in your commit log.
What exactly and in what way ?
> >   
> >   	/* Start the transfer */
> >   	reg = sun6i_spi_read(sspi, SUN6I_TFR_CTL_REG);
> > @@ -376,7 +381,9 @@ out:
> >   static irqreturn_t sun6i_spi_handler(int irq, void *dev_id)
> >   {
> >   	struct sun6i_spi *sspi = dev_id;
> > -	u32 status = sun6i_spi_read(sspi, SUN6I_INT_STA_REG);
> > +	u32 status;
> > +
> > +	status = sun6i_spi_read(sspi, SUN6I_INT_STA_REG);
> Why is this change needed?
A minor one, for readability.
> Maxime