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Subject: Re: [PATCH v3 3/6] spi: sun6i: restrict transfer length in PIO-mode
To:     Maxime Ripard <maxime.ripard@bootlin.com>
Cc:     Mark Brown <broonie@kernel.org>, Chen-Yu Tsai <wens@csie.org>,
        linux-spi@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org
References: <20180403154449.2443-1-ssuloev@orpaltech.com>
 <20180403154449.2443-4-ssuloev@orpaltech.com>
 <20180404065048.n76r3ytuznd6fqsl@flea>
From:   Sergey Suloev <ssuloev@orpaltech.com>
Message-ID: <a6044902-8977-3ce1-d7d5-c6797341a5d0@orpaltech.com>
Date:   Wed, 4 Apr 2018 14:35:14 +0300
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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?

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
>