| Message ID | 20230419060639.38853-5-jaewon02.kim@samsung.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [v2,1/4] spi: s3c64xx: changed to PIO mode if there is no DMA | expand |
On 19/04/2023 08:06, 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@samsung.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) > { > void __iomem *regs = sdd->regs; > unsigned long val; > + unsigned long time; > 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); > - } You just added this code. Adding and immediately removing it, suggests this should be one patch. Best regards, Krzysztof
On 23. 4. 19. 17:21, Krzysztof Kozlowski wrote: > On 19/04/2023 08:06, 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@samsung.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) >> { >> void __iomem *regs = sdd->regs; >> unsigned long val; >> + unsigned long time; >> 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); >> - } > You just added this code. Adding and immediately removing it, suggests > this should be one patch. > This code has been moved, not removed. + 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); + } + } + > Best regards, > Krzysztof > > Thanks Jaewon Kim
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@samsung.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 > { > 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'. > + } > + } > + > 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? The rest looks good. Andi
On 19/04/2023 11:45, Jaewon Kim wrote: >>> static int s3c64xx_wait_for_pio(struct s3c64xx_spi_driver_data *sdd, >>> - struct spi_transfer *xfer) >>> + struct spi_transfer *xfer, int use_irq) >>> { >>> void __iomem *regs = sdd->regs; >>> unsigned long val; >>> + unsigned long time; >>> 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); >>> - } >> You just added this code. Adding and immediately removing it, suggests >> this should be one patch. >> > This code has been moved, not removed. Move consists of remove and add. Add it in correct place since beginning. Best regards, Krzysztof
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@samsung.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
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) { void __iomem *regs = sdd->regs; unsigned long val; + unsigned long time; 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); + } + } + 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; } do { + /* transfer size is greater than 32, change to IRQ mode */ + if (xfer->len > S3C64XX_SPI_POLLING_SIZE) + use_irq = 1; + + if (use_irq) { + reinit_completion(&sdd->xfer_completion); + + rdy_lv = xfer->len; + /* Setup RDY_FIFO trigger Level + * RDY_LVL = + * fifo_lvl up to 64 byte -> N bytes + * 128 byte -> RDY_LVL * 2 bytes + * 256 byte -> RDY_LVL * 4 bytes + */ + if (fifo_len == 128) + rdy_lv /= 2; + else if (fifo_len == 256) + rdy_lv /= 4; + + val = readl(sdd->regs + S3C64XX_SPI_MODE_CFG); + val &= ~S3C64XX_SPI_MODE_RX_RDY_LVL; + val |= (rdy_lv << S3C64XX_SPI_MODE_RX_RDY_LVL_SHIFT); + writel(val, sdd->regs + S3C64XX_SPI_MODE_CFG); + + /* Enable FIFO_RDY_EN IRQ */ + val = readl(sdd->regs + S3C64XX_SPI_INT_EN); + writel((val | S3C64XX_SPI_INT_RX_FIFORDY_EN), + sdd->regs + S3C64XX_SPI_INT_EN); + + } + spin_lock_irqsave(&sdd->lock, flags); /* Pending only which is to be done */ @@ -793,7 +837,7 @@ static int s3c64xx_spi_transfer_one(struct spi_master *master, if (use_dma) status = s3c64xx_wait_for_dma(sdd, xfer); else - status = s3c64xx_wait_for_pio(sdd, xfer); + status = s3c64xx_wait_for_pio(sdd, xfer, use_irq); if (status) { dev_err(&spi->dev, @@ -832,8 +876,8 @@ static int s3c64xx_spi_transfer_one(struct spi_master *master, if (xfer->rx_buf) xfer->rx_buf += xfer->len; - if (target_len > fifo_len) - xfer->len = fifo_len; + if (target_len >= fifo_len) + xfer->len = fifo_len - 1; else xfer->len = target_len; } @@ -1003,6 +1047,14 @@ static irqreturn_t s3c64xx_spi_irq(int irq, void *data) dev_err(&spi->dev, "TX underrun\n"); } + if (val & S3C64XX_SPI_ST_RX_FIFORDY) { + complete(&sdd->xfer_completion); + /* No pending clear irq, turn-off INT_EN_RX_FIFO_RDY */ + val = readl(sdd->regs + S3C64XX_SPI_INT_EN); + writel((val & ~S3C64XX_SPI_INT_RX_FIFORDY_EN), + sdd->regs + S3C64XX_SPI_INT_EN); + } + /* Clear the pending irq by setting and then clearing it */ writel(clr, sdd->regs + S3C64XX_SPI_PENDING_CLR); writel(0, sdd->regs + S3C64XX_SPI_PENDING_CLR);
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@samsung.com> --- drivers/spi/spi-s3c64xx.c | 82 ++++++++++++++++++++++++++++++++------- 1 file changed, 67 insertions(+), 15 deletions(-)