linux-kernel - Re: [PATCH v2 4/4] spi: s3c64xx: support interrupt based pio mode

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Message-ID: <eb08398b-8a58-1138-cd2e-be5dba613cc6@samsung.com>
Date:   Fri, 21 Apr 2023 12:05:02 +0900
From:   Jaewon Kim <jaewon02.kim@...sung.com>
To:     Andi Shyti <andi.shyti@...nel.org>
Cc:     Mark Brown <broonie@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Andi Shyti <andi@...zian.org>,
        Alim Akhtar <alim.akhtar@...sung.com>,
        linux-spi@...r.kernel.org, linux-samsung-soc@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Chanho Park <chanho61.park@...sung.com>
Subject: Re: [PATCH v2 4/4] spi: s3c64xx: support interrupt based pio mode

Hi Andy,


On 23. 4. 20. 01:03, Andi Shyti wrote:
> Hi Jaewon,
>
> On Wed, Apr 19, 2023 at 03:06:39PM +0900, Jaewon Kim wrote:
>> Interrupt based pio mode is supported to reduce CPU load.
>> If transfer size is larger than 32 byte, it is processed using interrupt.
>>
>> Signed-off-by: Jaewon Kim <jaewon02.kim@...sung.com>
>> ---
>>   drivers/spi/spi-s3c64xx.c | 82 ++++++++++++++++++++++++++++++++-------
>>   1 file changed, 67 insertions(+), 15 deletions(-)
>>
>> diff --git a/drivers/spi/spi-s3c64xx.c b/drivers/spi/spi-s3c64xx.c
>> index cf3060b2639b..ce1afb9a4ed4 100644
>> --- a/drivers/spi/spi-s3c64xx.c
>> +++ b/drivers/spi/spi-s3c64xx.c
>> @@ -58,6 +58,8 @@
>>   #define S3C64XX_SPI_MODE_BUS_TSZ_HALFWORD	(1<<17)
>>   #define S3C64XX_SPI_MODE_BUS_TSZ_WORD		(2<<17)
>>   #define S3C64XX_SPI_MODE_BUS_TSZ_MASK		(3<<17)
>> +#define S3C64XX_SPI_MODE_RX_RDY_LVL		GENMASK(16, 11)
>> +#define S3C64XX_SPI_MODE_RX_RDY_LVL_SHIFT	11
>>   #define S3C64XX_SPI_MODE_SELF_LOOPBACK		(1<<3)
>>   #define S3C64XX_SPI_MODE_RXDMA_ON		(1<<2)
>>   #define S3C64XX_SPI_MODE_TXDMA_ON		(1<<1)
>> @@ -114,6 +116,8 @@
>>   
>>   #define S3C64XX_SPI_TRAILCNT		S3C64XX_SPI_MAX_TRAILCNT
>>   
>> +#define S3C64XX_SPI_POLLING_SIZE	32
>> +
>>   #define msecs_to_loops(t) (loops_per_jiffy / 1000 * HZ * t)
>>   #define is_polling(x)	(x->cntrlr_info->polling)
>>   
>> @@ -552,10 +556,11 @@ static int s3c64xx_wait_for_dma(struct s3c64xx_spi_driver_data *sdd,
>>   }
>>   
>>   static int s3c64xx_wait_for_pio(struct s3c64xx_spi_driver_data *sdd,
>> -				struct spi_transfer *xfer)
>> +				struct spi_transfer *xfer, int use_irq)
> bool use_irq

Okay, I will change it to bool.

>
>>   {
>>   	void __iomem *regs = sdd->regs;
>>   	unsigned long val;
>> +	unsigned long time;
> this time is used only in "if (use_irq)" can you move its
> declaration under the if?
>
>>   	u32 status;
>>   	int loops;
>>   	u32 cpy_len;
>> @@ -563,17 +568,24 @@ static int s3c64xx_wait_for_pio(struct s3c64xx_spi_driver_data *sdd,
>>   	int ms;
>>   	u32 tx_time;
>>   
>> -	/* sleep during signal transfer time */
>> -	status = readl(regs + S3C64XX_SPI_STATUS);
>> -	if (RX_FIFO_LVL(status, sdd) < xfer->len) {
>> -		tx_time = (xfer->len * 8 * 1000 * 1000) / sdd->cur_speed;
>> -		usleep_range(tx_time / 2, tx_time);
>> -	}
>> -
>>   	/* millisecs to xfer 'len' bytes @ 'cur_speed' */
>>   	ms = xfer->len * 8 * 1000 / sdd->cur_speed;
>>   	ms += 10; /* some tolerance */
>>   
>> +	if (use_irq) {
>> +		val = msecs_to_jiffies(ms);
>> +		time = wait_for_completion_timeout(&sdd->xfer_completion, val);
>> +		if (!time)
>> +			return -EIO;
>> +	} else {
>> +		/* sleep during signal transfer time */
>> +		status = readl(regs + S3C64XX_SPI_STATUS);
>> +		if (RX_FIFO_LVL(status, sdd) < xfer->len) {
>> +			tx_time = (xfer->len * 8 * 1000 * 1000) / sdd->cur_speed;
>> +			usleep_range(tx_time / 2, tx_time);
> yeah... just use 'ms'.
As I mentioned in the previous mail, the unit of tx_time is us.
>
>> +		}
>> +	}
>> +
>>   	val = msecs_to_loops(ms);
>>   	do {
>>   		cpu_relax();
>> @@ -737,10 +749,13 @@ static int s3c64xx_spi_transfer_one(struct spi_master *master,
>>   	void *rx_buf = NULL;
>>   	int target_len = 0, origin_len = 0;
>>   	int use_dma = 0;
>> +	int use_irq = 0;
>>   	int status;
>>   	u32 speed;
>>   	u8 bpw;
>>   	unsigned long flags;
>> +	u32 rdy_lv;
>> +	u32 val;
>>   
>>   	reinit_completion(&sdd->xfer_completion);
>>   
>> @@ -761,17 +776,46 @@ static int s3c64xx_spi_transfer_one(struct spi_master *master,
>>   	    sdd->rx_dma.ch && sdd->tx_dma.ch) {
>>   		use_dma = 1;
>>   
>> -	} else if (xfer->len > fifo_len) {
>> +	} else if (xfer->len >= fifo_len) {
>>   		tx_buf = xfer->tx_buf;
>>   		rx_buf = xfer->rx_buf;
>>   		origin_len = xfer->len;
>> -
>>   		target_len = xfer->len;
>> -		if (xfer->len > fifo_len)
>> -			xfer->len = fifo_len;
>> +		xfer->len = fifo_len - 1;
>>   	}
> Is this change related to this patch?

Yes, it is related to this patch.

If data is filled as much as the size of FIFO, underrun/overrun IRQ occurs.

In CPU polling mode, it did not occur because the FIFO was read before 
the IRQ was set.

So, I set xfer->len to fifo_len-1.

>
> The rest looks good.
>
> Andi


Thanks

Jaewon Kim