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

[Sergey Suloev]

On 04/05/2018 12:19 PM, Maxime Ripard wrote:
> On Wed, Apr 04, 2018 at 02:35:14PM +0300, Sergey Suloev wrote:
> > 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?
> Why do you need to revert that change.
>
> > Change is supposed to restrict max transfer size for PIO mode otherwise it
> > will fail.
> > The maximum transfer length = FIFO depth for PIO mode.
> The point of that patch was precisely to allow to send more data than
> the FIFO. You're breaking that behaviour without any justification,
> and this is not ok.

I am sorry, but you can't. That's a hardware limitation.
> > > >    }
> > > >    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
> The fact that it's more appropriate should be justified.
>
> > > >    	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 ?
> You should explain, at least:
> A) What is the current behaviour
> B) Why that is a problem, or what problem does it cause
> C) What solution you implement and why you think it's justified
>
> > > >    	/* 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.
> That's arguable, and you should have a single logical change per
> patch. So this doesn't belong in this one.
>
> Maxime
>
>
>
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