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SubjectRe: [PATCH v3 3/6] spi: sun6i: restrict transfer length in PIO-mode
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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@orpaltech.com>
>>>> ---
>>>> 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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> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel


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