[PATCH v2 0/6] spi: Add support for DMA transfers in sun4i SPI driver

[PATCH v2 0/6] spi: Add support for DMA transfers in sun4i SPI driver

[Sergey Suloev]

The following patchset provides corrections for PIO-mode
and support for DMA transfers in sun4i SPI driver.

Changes in v2:
1) Restored processing of 3/4 FIFO full interrupt.

2) Debug log enhancements.

Sergey Suloev (6):
  spi: core: handle timeout error from transfer_one()
  spi: sun4i: restrict transfer length in PIO-mode
  spi: sun4i: coding style/readability improvements
  spi: sun4i: use completion provided by SPI core driver
  spi: sun4i: introduce register set/unset helpers
  spi: sun4i: add DMA transfers support

 drivers/spi/spi-sun4i.c | 442 +++++++++++++++++++++++++++++++++++++-----------
 drivers/spi/spi.c       |   5 +-
 2 files changed, 347 insertions(+), 100 deletions(-)

-- 
2.16.2

[PATCH v2 1/6] spi: core: handle timeout error from transfer_one()

[Sergey Suloev]

As long as sun4i/sun6i SPI drivers have overriden the default
"wait for completion" procedure then we need to properly
handle -ETIMEDOUT error from transfer_one().

Signed-off-by: Sergey Suloev <ssuloev@orpaltech.com>
---
 drivers/spi/spi.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index b33a727..2dcd4f6 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -1028,7 +1028,7 @@ static int spi_transfer_one_message(struct spi_controller *ctlr,
 			reinit_completion(&ctlr->xfer_completion);
 
 			ret = ctlr->transfer_one(ctlr, msg->spi, xfer);
-			if (ret < 0) {
+			if (ret < 0 && ret != -ETIMEDOUT) {
 				SPI_STATISTICS_INCREMENT_FIELD(statm,
 							       errors);
 				SPI_STATISTICS_INCREMENT_FIELD(stats,
@@ -1051,7 +1051,7 @@ static int spi_transfer_one_message(struct spi_controller *ctlr,
 								 msecs_to_jiffies(ms));
 			}
 
-			if (ms == 0) {
+			if (ms == 0 || ret == -ETIMEDOUT) {
 				SPI_STATISTICS_INCREMENT_FIELD(statm,
 							       timedout);
 				SPI_STATISTICS_INCREMENT_FIELD(stats,
@@ -1059,6 +1059,7 @@ static int spi_transfer_one_message(struct spi_controller *ctlr,
 				dev_err(&msg->spi->dev,
 					"SPI transfer timed out\n");
 				msg->status = -ETIMEDOUT;
+				ret = 0;
 			}
 		} else {
 			if (xfer->len)
-- 
2.16.2

[PATCH v2 2/6] spi: sun4i: restrict transfer length in PIO-mode

[Sergey Suloev]

There is no need to handle the 3/4 FIFO empty interrupt
as the maximum supported transfer length in PIO mode
is 64 bytes.
As long as a problem was reported previously with filling FIFO
on A10s we want to stick with 63 bytes depth.

Changes in v2:
1) Restored processing of 3/4 FIFO full interrupt.

Signed-off-by: Sergey Suloev <ssuloev@orpaltech.com>
---
 drivers/spi/spi-sun4i.c | 37 ++++++++++---------------------------
 1 file changed, 10 insertions(+), 27 deletions(-)

diff --git a/drivers/spi/spi-sun4i.c b/drivers/spi/spi-sun4i.c
index 4141003..08fd007 100644
--- a/drivers/spi/spi-sun4i.c
+++ b/drivers/spi/spi-sun4i.c
@@ -22,7 +22,12 @@
 
 #include <linux/spi/spi.h>
 
-#define SUN4I_FIFO_DEPTH		64
+/*
+ * FIFO length is 64 bytes
+ * But filling the FIFO fully might cause a timeout
+ * on some devices, for example on spi2 on A10s
+ */
+#define SUN4I_FIFO_DEPTH		63
 
 #define SUN4I_RXDATA_REG		0x00
 
@@ -202,7 +207,7 @@ static void sun4i_spi_set_cs(struct spi_device *spi, bool enable)
 
 static size_t sun4i_spi_max_transfer_size(struct spi_device *spi)
 {
-	return SUN4I_FIFO_DEPTH - 1;
+	return SUN4I_FIFO_DEPTH;
 }
 
 static int sun4i_spi_transfer_one(struct spi_master *master,
@@ -216,11 +221,8 @@ static int sun4i_spi_transfer_one(struct spi_master *master,
 	int ret = 0;
 	u32 reg;
 
-	/* We don't support transfer larger than the FIFO */
-	if (tfr->len > SUN4I_MAX_XFER_SIZE)
-		return -EMSGSIZE;
-
-	if (tfr->tx_buf && tfr->len >= SUN4I_MAX_XFER_SIZE)
+	/* We don't support transfers larger than FIFO depth */
+	if (tfr->len > SUN4I_FIFO_DEPTH)
 		return -EMSGSIZE;
 
 	reinit_completion(&sspi->done);
@@ -313,17 +315,12 @@ static int sun4i_spi_transfer_one(struct spi_master *master,
 
 	/*
 	 * Fill the TX FIFO
-	 * Filling the FIFO fully causes timeout for some reason
-	 * at least on spi2 on A10s
 	 */
-	sun4i_spi_fill_fifo(sspi, SUN4I_FIFO_DEPTH - 1);
+	sun4i_spi_fill_fifo(sspi, SUN4I_FIFO_DEPTH);
 
 	/* Enable the interrupts */
 	sun4i_spi_enable_interrupt(sspi, SUN4I_INT_CTL_TC |
 					 SUN4I_INT_CTL_RF_F34);
-	/* Only enable Tx FIFO interrupt if we really need it */
-	if (tx_len > SUN4I_FIFO_DEPTH)
-		sun4i_spi_enable_interrupt(sspi, SUN4I_INT_CTL_TF_E34);
 
 	/* Start the transfer */
 	reg = sun4i_spi_read(sspi, SUN4I_CTL_REG);
@@ -371,20 +368,6 @@ static irqreturn_t sun4i_spi_handler(int irq, void *dev_id)
 		return IRQ_HANDLED;
 	}
 
-	/* Transmit FIFO 3/4 empty */
-	if (status & SUN4I_INT_CTL_TF_E34) {
-		sun4i_spi_fill_fifo(sspi, SUN4I_FIFO_DEPTH);
-
-		if (!sspi->len)
-			/* nothing left to transmit */
-			sun4i_spi_disable_interrupt(sspi, SUN4I_INT_CTL_TF_E34);
-
-		/* Only clear the interrupt _after_ re-seeding the FIFO */
-		sun4i_spi_write(sspi, SUN4I_INT_STA_REG, SUN4I_INT_CTL_TF_E34);
-
-		return IRQ_HANDLED;
-	}
-
 	return IRQ_NONE;
 }
 
-- 
2.16.2

[PATCH v2 3/6] spi: sun4i: coding style/readability improvements

[Sergey Suloev]

Minor changes to fulfill the coding style and
improve the readability.

Signed-off-by: Sergey Suloev <ssuloev@orpaltech.com>
---
 drivers/spi/spi-sun4i.c | 32 +++++++++++++++++---------------
 1 file changed, 17 insertions(+), 15 deletions(-)

diff --git a/drivers/spi/spi-sun4i.c b/drivers/spi/spi-sun4i.c
index 08fd007..899e956 100644
--- a/drivers/spi/spi-sun4i.c
+++ b/drivers/spi/spi-sun4i.c
@@ -83,8 +83,11 @@
 #define SUN4I_FIFO_STA_TF_CNT_MASK		0x7f
 #define SUN4I_FIFO_STA_TF_CNT_BITS		16
 
+#define SUN4I_SPI_MAX_SPEED_HZ		100 * 1000 * 1000
+#define SUN4I_SPI_MIN_SPEED_HZ		3 * 1000
+#define SUN4I_SPI_MODE_BITS		(SPI_CPOL | SPI_CPHA | SPI_CS_HIGH | SPI_LSB_FIRST)
+
 struct sun4i_spi {
-	struct spi_master	*master;
 	void __iomem		*base_addr;
 	struct clk		*hclk;
 	struct clk		*mclk;
@@ -418,12 +421,23 @@ static int sun4i_spi_probe(struct platform_device *pdev)
 	struct resource	*res;
 	int ret = 0, irq;
 
-	master = spi_alloc_master(&pdev->dev, sizeof(struct sun4i_spi));
+	master = spi_alloc_master(&pdev->dev, sizeof(*sspi));
 	if (!master) {
 		dev_err(&pdev->dev, "Unable to allocate SPI Master\n");
 		return -ENOMEM;
 	}
 
+	master->max_speed_hz = SUN4I_SPI_MAX_SPEED_HZ;
+	master->min_speed_hz = SUN4I_SPI_MIN_SPEED_HZ;
+	master->num_chipselect = 4;
+	master->mode_bits = SUN4I_SPI_MODE_BITS;
+	master->bits_per_word_mask = SPI_BPW_MASK(8);
+	master->set_cs = sun4i_spi_set_cs;
+	master->transfer_one = sun4i_spi_transfer_one;
+	master->max_transfer_size = sun4i_spi_max_transfer_size;
+	master->dev.of_node = pdev->dev.of_node;
+	master->auto_runtime_pm = true;
+
 	platform_set_drvdata(pdev, master);
 	sspi = spi_master_get_devdata(master);
 
@@ -442,24 +456,12 @@ static int sun4i_spi_probe(struct platform_device *pdev)
 	}
 
 	ret = devm_request_irq(&pdev->dev, irq, sun4i_spi_handler,
-			       0, "sun4i-spi", sspi);
+			       0, dev_name(&pdev->dev), sspi);
 	if (ret) {
 		dev_err(&pdev->dev, "Cannot request IRQ\n");
 		goto err_free_master;
 	}
 
-	sspi->master = master;
-	master->max_speed_hz = 100 * 1000 * 1000;
-	master->min_speed_hz = 3 * 1000;
-	master->set_cs = sun4i_spi_set_cs;
-	master->transfer_one = sun4i_spi_transfer_one;
-	master->num_chipselect = 4;
-	master->mode_bits = SPI_CPOL | SPI_CPHA | SPI_CS_HIGH | SPI_LSB_FIRST;
-	master->bits_per_word_mask = SPI_BPW_MASK(8);
-	master->dev.of_node = pdev->dev.of_node;
-	master->auto_runtime_pm = true;
-	master->max_transfer_size = sun4i_spi_max_transfer_size;
-
 	sspi->hclk = devm_clk_get(&pdev->dev, "ahb");
 	if (IS_ERR(sspi->hclk)) {
 		dev_err(&pdev->dev, "Unable to acquire AHB clock\n");
-- 
2.16.2

[PATCH v2 4/6] spi: sun4i: use completion provided by SPI core driver

[Sergey Suloev]

As long as the completion already provided by the SPI core
then there is no need to waste extra-memory on this.
Also a waiting function was added to avoid code duplication.

Signed-off-by: Sergey Suloev <ssuloev@orpaltech.com>
---
 drivers/spi/spi-sun4i.c | 62 ++++++++++++++++++++++++++++---------------------
 1 file changed, 35 insertions(+), 27 deletions(-)

diff --git a/drivers/spi/spi-sun4i.c b/drivers/spi/spi-sun4i.c
index 899e956..9d1bc20 100644
--- a/drivers/spi/spi-sun4i.c
+++ b/drivers/spi/spi-sun4i.c
@@ -92,8 +92,6 @@ struct sun4i_spi {
 	struct clk		*hclk;
 	struct clk		*mclk;
 
-	struct completion	done;
-
 	const u8		*tx_buf;
 	u8			*rx_buf;
 	int			len;
@@ -213,13 +211,36 @@ static size_t sun4i_spi_max_transfer_size(struct spi_device *spi)
 	return SUN4I_FIFO_DEPTH;
 }
 
+static int sun4i_spi_wait_for_transfer(struct spi_device *spi,
+				       struct spi_transfer *tfr)
+{
+	struct spi_master *master = spi->master;
+	unsigned int start, end, tx_time;
+	unsigned int timeout;
+
+	/* calc required timeout from given speed & len values */
+	tx_time = max(tfr->len * 8 * 2 / (tfr->speed_hz / 1000), 100U);
+	start = jiffies;
+	timeout = wait_for_completion_timeout(&master->xfer_completion,
+					      msecs_to_jiffies(tx_time));
+	end = jiffies;
+	if (!timeout) {
+		dev_warn(&master->dev,
+			 "%s: timeout transferring %u bytes@%iHz for %i(%i)ms",
+			 dev_name(&spi->dev), tfr->len, tfr->speed_hz,
+			 jiffies_to_msecs(end - start), tx_time);
+		return -ETIMEDOUT;
+	}
+
+	return 0;
+}
+
 static int sun4i_spi_transfer_one(struct spi_master *master,
 				  struct spi_device *spi,
 				  struct spi_transfer *tfr)
 {
 	struct sun4i_spi *sspi = spi_master_get_devdata(master);
-	unsigned int mclk_rate, div, timeout;
-	unsigned int start, end, tx_time;
+	unsigned int mclk_rate, div;
 	unsigned int tx_len = 0;
 	int ret = 0;
 	u32 reg;
@@ -228,7 +249,6 @@ static int sun4i_spi_transfer_one(struct spi_master *master,
 	if (tfr->len > SUN4I_FIFO_DEPTH)
 		return -EMSGSIZE;
 
-	reinit_completion(&sspi->done);
 	sspi->tx_buf = tfr->tx_buf;
 	sspi->rx_buf = tfr->rx_buf;
 	sspi->len = tfr->len;
@@ -329,22 +349,8 @@ static int sun4i_spi_transfer_one(struct spi_master *master,
 	reg = sun4i_spi_read(sspi, SUN4I_CTL_REG);
 	sun4i_spi_write(sspi, SUN4I_CTL_REG, reg | SUN4I_CTL_XCH);
 
-	tx_time = max(tfr->len * 8 * 2 / (tfr->speed_hz / 1000), 100U);
-	start = jiffies;
-	timeout = wait_for_completion_timeout(&sspi->done,
-					      msecs_to_jiffies(tx_time));
-	end = jiffies;
-	if (!timeout) {
-		dev_warn(&master->dev,
-			 "%s: timeout transferring %u bytes@%iHz for %i(%i)ms",
-			 dev_name(&spi->dev), tfr->len, tfr->speed_hz,
-			 jiffies_to_msecs(end - start), tx_time);
-		ret = -ETIMEDOUT;
-		goto out;
-	}
-
+	ret = sun4i_spi_wait_for_transfer(spi, tfr);
 
-out:
 	sun4i_spi_write(sspi, SUN4I_INT_CTL_REG, 0);
 
 	return ret;
@@ -352,14 +358,18 @@ out:
 
 static irqreturn_t sun4i_spi_handler(int irq, void *dev_id)
 {
-	struct sun4i_spi *sspi = dev_id;
-	u32 status = sun4i_spi_read(sspi, SUN4I_INT_STA_REG);
+	struct spi_master *master = dev_id;
+	struct sun4i_spi *sspi = spi_master_get_devdata(master);
+	u32 status;
+
+	status = sun4i_spi_read(sspi, SUN4I_INT_STA_REG);
 
 	/* Transfer complete */
 	if (status & SUN4I_INT_CTL_TC) {
-		sun4i_spi_write(sspi, SUN4I_INT_STA_REG, SUN4I_INT_CTL_TC);
+		sun4i_spi_write(sspi, SUN4I_INT_STA_REG,
+				SUN4I_INT_CTL_TC);
 		sun4i_spi_drain_fifo(sspi, SUN4I_FIFO_DEPTH);
-		complete(&sspi->done);
+		spi_finalize_current_transfer(master);
 		return IRQ_HANDLED;
 	}
 
@@ -456,7 +466,7 @@ static int sun4i_spi_probe(struct platform_device *pdev)
 	}
 
 	ret = devm_request_irq(&pdev->dev, irq, sun4i_spi_handler,
-			       0, dev_name(&pdev->dev), sspi);
+			       0, dev_name(&pdev->dev), master);
 	if (ret) {
 		dev_err(&pdev->dev, "Cannot request IRQ\n");
 		goto err_free_master;
@@ -476,8 +486,6 @@ static int sun4i_spi_probe(struct platform_device *pdev)
 		goto err_free_master;
 	}
 
-	init_completion(&sspi->done);
-
 	/*
 	 * This wake-up/shutdown pattern is to be able to have the
 	 * device woken up, even if runtime_pm is disabled
-- 
2.16.2

[PATCH v2 5/6] spi: sun4i: introduce register set/unset helpers

[Sergey Suloev]

Two helper functions were added in order to set/unset
specified flags in registers.

Signed-off-by: Sergey Suloev <ssuloev@orpaltech.com>
---
 drivers/spi/spi-sun4i.c | 40 +++++++++++++++++++---------------------
 1 file changed, 19 insertions(+), 21 deletions(-)

diff --git a/drivers/spi/spi-sun4i.c b/drivers/spi/spi-sun4i.c
index 9d1bc20..d81d31c 100644
--- a/drivers/spi/spi-sun4i.c
+++ b/drivers/spi/spi-sun4i.c
@@ -107,29 +107,29 @@ static inline void sun4i_spi_write(struct sun4i_spi *sspi, u32 reg, u32 value)
 	writel(value, sspi->base_addr + reg);
 }
 
-static inline u32 sun4i_spi_get_tx_fifo_count(struct sun4i_spi *sspi)
+static inline void sun4i_spi_set(struct sun4i_spi *sspi, u32 addr, u32 val)
 {
-	u32 reg = sun4i_spi_read(sspi, SUN4I_FIFO_STA_REG);
-
-	reg >>= SUN4I_FIFO_STA_TF_CNT_BITS;
+	u32 reg = sun4i_spi_read(sspi, addr);
 
-	return reg & SUN4I_FIFO_STA_TF_CNT_MASK;
+	reg |= val;
+	sun4i_spi_write(sspi, addr, reg);
 }
 
-static inline void sun4i_spi_enable_interrupt(struct sun4i_spi *sspi, u32 mask)
+static inline void sun4i_spi_unset(struct sun4i_spi *sspi, u32 addr, u32 val)
 {
-	u32 reg = sun4i_spi_read(sspi, SUN4I_INT_CTL_REG);
+	u32 reg = sun4i_spi_read(sspi, addr);
 
-	reg |= mask;
-	sun4i_spi_write(sspi, SUN4I_INT_CTL_REG, reg);
+	reg &= ~val;
+	sun4i_spi_write(sspi, addr, reg);
 }
 
-static inline void sun4i_spi_disable_interrupt(struct sun4i_spi *sspi, u32 mask)
+static inline u32 sun4i_spi_get_tx_fifo_count(struct sun4i_spi *sspi)
 {
-	u32 reg = sun4i_spi_read(sspi, SUN4I_INT_CTL_REG);
+	u32 reg = sun4i_spi_read(sspi, SUN4I_FIFO_STA_REG);
 
-	reg &= ~mask;
-	sun4i_spi_write(sspi, SUN4I_INT_CTL_REG, reg);
+	reg >>= SUN4I_FIFO_STA_TF_CNT_BITS;
+
+	return reg & SUN4I_FIFO_STA_TF_CNT_MASK;
 }
 
 static inline void sun4i_spi_drain_fifo(struct sun4i_spi *sspi, int len)
@@ -256,13 +256,12 @@ static int sun4i_spi_transfer_one(struct spi_master *master,
 	/* Clear pending interrupts */
 	sun4i_spi_write(sspi, SUN4I_INT_STA_REG, ~0);
 
+	/* Reset FIFOs */
+	sun4i_spi_set(sspi, SUN4I_CTL_REG,
+		      SUN4I_CTL_RF_RST | SUN4I_CTL_TF_RST);
 
 	reg = sun4i_spi_read(sspi, SUN4I_CTL_REG);
 
-	/* Reset FIFOs */
-	sun4i_spi_write(sspi, SUN4I_CTL_REG,
-			reg | SUN4I_CTL_RF_RST | SUN4I_CTL_TF_RST);
-
 	/*
 	 * Setup the transfer control register: Chip Select,
 	 * polarities, etc.
@@ -342,12 +341,11 @@ static int sun4i_spi_transfer_one(struct spi_master *master,
 	sun4i_spi_fill_fifo(sspi, SUN4I_FIFO_DEPTH);
 
 	/* Enable the interrupts */
-	sun4i_spi_enable_interrupt(sspi, SUN4I_INT_CTL_TC |
-					 SUN4I_INT_CTL_RF_F34);
+	sun4i_spi_set(sspi, SUN4I_INT_CTL_REG, SUN4I_INT_CTL_TC |
+					       SUN4I_INT_CTL_RF_F34);
 
 	/* Start the transfer */
-	reg = sun4i_spi_read(sspi, SUN4I_CTL_REG);
-	sun4i_spi_write(sspi, SUN4I_CTL_REG, reg | SUN4I_CTL_XCH);
+	sun4i_spi_set(sspi, SUN4I_CTL_REG, SUN4I_CTL_XCH);
 
 	ret = sun4i_spi_wait_for_transfer(spi, tfr);
 
-- 
2.16.2

[PATCH v2 6/6] spi: sun4i: add DMA transfers support

[Sergey Suloev]

DMA transfers are now available for sun4i-family SoCs.
The DMA mode is used automatically as soon as requested
transfer length is more than FIFO length.

Changes in v2:
1) Debug log enhancements.

Signed-off-by: Sergey Suloev <ssuloev@orpaltech.com>
---
 drivers/spi/spi-sun4i.c | 299 ++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 277 insertions(+), 22 deletions(-)

diff --git a/drivers/spi/spi-sun4i.c b/drivers/spi/spi-sun4i.c
index d81d31c..dda7922 100644
--- a/drivers/spi/spi-sun4i.c
+++ b/drivers/spi/spi-sun4i.c
@@ -14,6 +14,8 @@
 #include <linux/clk.h>
 #include <linux/delay.h>
 #include <linux/device.h>
+#include <linux/dmaengine.h>
+#include <linux/dma-mapping.h>
 #include <linux/interrupt.h>
 #include <linux/io.h>
 #include <linux/module.h>
@@ -39,6 +41,7 @@
 #define SUN4I_CTL_CPHA				BIT(2)
 #define SUN4I_CTL_CPOL				BIT(3)
 #define SUN4I_CTL_CS_ACTIVE_LOW			BIT(4)
+#define SUN4I_CTL_DMA_DEDICATED			BIT(5)
 #define SUN4I_CTL_LMTF				BIT(6)
 #define SUN4I_CTL_TF_RST			BIT(8)
 #define SUN4I_CTL_RF_RST			BIT(9)
@@ -58,6 +61,8 @@
 #define SUN4I_INT_STA_REG		0x10
 
 #define SUN4I_DMA_CTL_REG		0x14
+#define SUN4I_CTL_DMA_RF_READY			BIT(0)
+#define SUN4I_CTL_DMA_TF_NOT_FULL		BIT(10)
 
 #define SUN4I_WAIT_REG			0x18
 
@@ -169,6 +174,13 @@ static inline void sun4i_spi_fill_fifo(struct sun4i_spi *sspi, int len)
 	}
 }
 
+static bool sun4i_spi_can_dma(struct spi_master *master,
+			      struct spi_device *spi,
+			      struct spi_transfer *tfr)
+{
+	return tfr->len > SUN4I_FIFO_DEPTH;
+}
+
 static void sun4i_spi_set_cs(struct spi_device *spi, bool enable)
 {
 	struct sun4i_spi *sspi = spi_master_get_devdata(spi->master);
@@ -208,6 +220,11 @@ static void sun4i_spi_set_cs(struct spi_device *spi, bool enable)
 
 static size_t sun4i_spi_max_transfer_size(struct spi_device *spi)
 {
+	struct spi_master *master = spi->master;
+
+	if (master->can_dma)
+		return SUN4I_MAX_XFER_SIZE;
+
 	return SUN4I_FIFO_DEPTH;
 }
 
@@ -235,6 +252,164 @@ static int sun4i_spi_wait_for_transfer(struct spi_device *spi,
 	return 0;
 }
 
+static void sun4i_spi_dma_callback(void *param)
+{
+	struct spi_master *master = param;
+
+	dev_dbg(&master->dev, "DMA transfer complete\n");
+	spi_finalize_current_transfer(master);
+}
+
+static int sun4i_spi_dmap_prep_tx(struct spi_master *master,
+				  struct spi_transfer *tfr,
+				  dma_cookie_t *cookie)
+{
+	struct dma_async_tx_descriptor *chan_desc = NULL;
+
+	chan_desc = dmaengine_prep_slave_sg(master->dma_tx,
+					    tfr->tx_sg.sgl, tfr->tx_sg.nents,
+					    DMA_TO_DEVICE,
+					    DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
+	if (!chan_desc) {
+		dev_err(&master->dev,
+			"Couldn't prepare TX DMA slave\n");
+		return -EIO;
+	}
+
+	chan_desc->callback = sun4i_spi_dma_callback;
+	chan_desc->callback_param = master;
+
+	*cookie = dmaengine_submit(chan_desc);
+	dma_async_issue_pending(master->dma_tx);
+
+	return 0;
+}
+
+static int sun4i_spi_dmap_prep_rx(struct spi_master *master,
+				  struct spi_transfer *tfr,
+				  dma_cookie_t *cookie)
+{
+	struct dma_async_tx_descriptor *chan_desc = NULL;
+
+	chan_desc = dmaengine_prep_slave_sg(master->dma_rx,
+					    tfr->rx_sg.sgl, tfr->rx_sg.nents,
+					    DMA_FROM_DEVICE,
+					    DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
+	if (!chan_desc) {
+		dev_err(&master->dev,
+			"Couldn't prepare RX DMA slave\n");
+		return -EIO;
+	}
+
+	chan_desc->callback = sun4i_spi_dma_callback;
+	chan_desc->callback_param = master;
+
+	*cookie = dmaengine_submit(chan_desc);
+	dma_async_issue_pending(master->dma_rx);
+
+	return 0;
+}
+
+static int sun4i_spi_transfer_one_dma(struct spi_device *spi,
+				      struct spi_transfer *tfr)
+{
+	struct spi_master *master = spi->master;
+	struct sun4i_spi *sspi = spi_master_get_devdata(master);
+	dma_cookie_t tx_cookie = 0, rx_cookie = 0;
+	enum dma_status status;
+	int ret;
+	u32 reg = 0;
+
+	dev_dbg(&master->dev, "Using DMA mode for transfer\n");
+
+	/* Disable interrupts */
+	sun4i_spi_write(sspi, SUN4I_INT_CTL_REG, 0);
+
+	if (sspi->tx_buf) {
+		ret = sun4i_spi_dmap_prep_tx(master, tfr, &tx_cookie);
+		if (ret)
+			goto out;
+
+		reg |= SUN4I_CTL_DMA_TF_NOT_FULL;
+	}
+
+	if (sspi->rx_buf) {
+		ret = sun4i_spi_dmap_prep_rx(master, tfr, &rx_cookie);
+		if (ret)
+			goto out;
+
+		reg |= SUN4I_CTL_DMA_RF_READY;
+	}
+
+	sun4i_spi_write(sspi, SUN4I_DMA_CTL_REG, reg);
+
+	/* Dedicated DMA requests */
+	sun4i_spi_set(sspi, SUN4I_CTL_REG, SUN4I_CTL_DMA_DEDICATED);
+
+	/* Start transfer */
+	sun4i_spi_set(sspi, SUN4I_CTL_REG, SUN4I_CTL_XCH);
+
+	/* Wait for completion */
+	ret = sun4i_spi_wait_for_transfer(spi, tfr);
+	if (ret)
+		goto out;
+
+	if (sspi->tx_buf && (status = dma_async_is_tx_complete(master->dma_tx,
+			tx_cookie, NULL, NULL))) {
+		dev_warn(&master->dev,
+			"DMA returned completion status of: %s\n",
+			status == DMA_ERROR ? "error" : "in progress");
+	}
+	if (sspi->rx_buf && (status = dma_async_is_tx_complete(master->dma_rx,
+			rx_cookie, NULL, NULL))) {
+		dev_warn(&master->dev,
+			"DMA returned completion status of: %s\n",
+			status == DMA_ERROR ? "error" : "in progress");
+	}
+
+out:
+	if (ret) {
+		dev_dbg(&master->dev, "DMA channel teardown\n");
+
+		if (sspi->tx_buf)
+			dmaengine_terminate_sync(master->dma_tx);
+		if (sspi->rx_buf)
+			dmaengine_terminate_sync(master->dma_rx);
+	}
+
+	sun4i_spi_drain_fifo(sspi, SUN4I_FIFO_DEPTH);
+
+	return ret;
+}
+
+static int sun4i_spi_transfer_one_pio(struct spi_device *spi,
+				      struct spi_transfer *tfr)
+{
+	struct spi_master *master = spi->master;
+	struct sun4i_spi *sspi = spi_master_get_devdata(master);
+	int ret;
+
+	/* Explicit disable DMA requests */
+	sun4i_spi_write(sspi, SUN4I_DMA_CTL_REG, 0);
+	sun4i_spi_unset(sspi, SUN4I_CTL_REG, SUN4I_CTL_DMA_DEDICATED);
+
+	/* Fill the TX FIFO */
+	sun4i_spi_fill_fifo(sspi, SUN4I_FIFO_DEPTH);
+
+	/* Enable the interrupts */
+	sun4i_spi_set(sspi, SUN4I_INT_CTL_REG, SUN4I_INT_CTL_TC |
+					       SUN4I_INT_CTL_RF_F34);
+
+	/* Start transfer */
+	sun4i_spi_set(sspi, SUN4I_CTL_REG, SUN4I_CTL_XCH);
+
+	ret = sun4i_spi_wait_for_transfer(spi, tfr);
+
+	sun4i_spi_write(sspi, SUN4I_INT_CTL_REG, 0);
+
+	return ret;
+}
+
 static int sun4i_spi_transfer_one(struct spi_master *master,
 				  struct spi_device *spi,
 				  struct spi_transfer *tfr)
@@ -242,13 +417,22 @@ static int sun4i_spi_transfer_one(struct spi_master *master,
 	struct sun4i_spi *sspi = spi_master_get_devdata(master);
 	unsigned int mclk_rate, div;
 	unsigned int tx_len = 0;
-	int ret = 0;
 	u32 reg;
 
-	/* We don't support transfers larger than FIFO depth */
-	if (tfr->len > SUN4I_FIFO_DEPTH)
+	/* A zero length transfer never finishes if programmed
+	   in the hardware */
+	if (!tfr->len)
+		return 0;
+
+	if (tfr->len > SUN4I_MAX_XFER_SIZE)
 		return -EMSGSIZE;
 
+	if (!master->can_dma) {
+		/* Don't support transfer larger than the FIFO */
+		if (tfr->len > SUN4I_FIFO_DEPTH)
+			return -EMSGSIZE;
+	}
+
 	sspi->tx_buf = tfr->tx_buf;
 	sspi->rx_buf = tfr->rx_buf;
 	sspi->len = tfr->len;
@@ -335,23 +519,10 @@ static int sun4i_spi_transfer_one(struct spi_master *master,
 	sun4i_spi_write(sspi, SUN4I_BURST_CNT_REG, SUN4I_BURST_CNT(tfr->len));
 	sun4i_spi_write(sspi, SUN4I_XMIT_CNT_REG, SUN4I_XMIT_CNT(tx_len));
 
-	/*
-	 * Fill the TX FIFO
-	 */
-	sun4i_spi_fill_fifo(sspi, SUN4I_FIFO_DEPTH);
-
-	/* Enable the interrupts */
-	sun4i_spi_set(sspi, SUN4I_INT_CTL_REG, SUN4I_INT_CTL_TC |
-					       SUN4I_INT_CTL_RF_F34);
-
-	/* Start the transfer */
-	sun4i_spi_set(sspi, SUN4I_CTL_REG, SUN4I_CTL_XCH);
-
-	ret = sun4i_spi_wait_for_transfer(spi, tfr);
-
-	sun4i_spi_write(sspi, SUN4I_INT_CTL_REG, 0);
+	if (sun4i_spi_can_dma(master, spi, tfr))
+		return sun4i_spi_transfer_one_dma(spi, tfr);
 
-	return ret;
+	return sun4i_spi_transfer_one_pio(spi, tfr);
 }
 
 static irqreturn_t sun4i_spi_handler(int irq, void *dev_id)
@@ -364,8 +535,7 @@ static irqreturn_t sun4i_spi_handler(int irq, void *dev_id)
 
 	/* Transfer complete */
 	if (status & SUN4I_INT_CTL_TC) {
-		sun4i_spi_write(sspi, SUN4I_INT_STA_REG,
-				SUN4I_INT_CTL_TC);
+		sun4i_spi_write(sspi, SUN4I_INT_STA_REG, SUN4I_INT_CTL_TC);
 		sun4i_spi_drain_fifo(sspi, SUN4I_FIFO_DEPTH);
 		spi_finalize_current_transfer(master);
 		return IRQ_HANDLED;
@@ -422,6 +592,76 @@ static int sun4i_spi_runtime_suspend(struct device *dev)
 	return 0;
 }
 
+static int sun4i_spi_dma_setup(struct device *dev,
+			       struct resource *res)
+{
+	struct spi_master *master = dev_get_drvdata(dev);
+	struct dma_slave_config dma_sconf;
+	int ret;
+
+	master->dma_tx = dma_request_slave_channel_reason(dev, "tx");
+	if (IS_ERR(master->dma_tx)) {
+		dev_err(dev, "Unable to acquire DMA TX channel\n");
+		ret = PTR_ERR(master->dma_tx);
+		goto out;
+	}
+
+	dma_sconf.direction = DMA_MEM_TO_DEV;
+	dma_sconf.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
+	dma_sconf.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
+	dma_sconf.dst_addr = res->start + SUN4I_TXDATA_REG;
+	dma_sconf.dst_maxburst = 1;
+	dma_sconf.src_maxburst = 1;
+
+	ret = dmaengine_slave_config(master->dma_tx, &dma_sconf);
+	if (ret) {
+		dev_err(dev, "Unable to configure DMA TX slave\n");
+		goto err_rel_tx;
+	}
+
+	master->dma_rx = dma_request_slave_channel_reason(dev, "rx");
+	if (IS_ERR(master->dma_rx)) {
+		dev_err(dev, "Unable to acquire DMA RX channel\n");
+		ret = PTR_ERR(master->dma_rx);
+		goto err_rel_tx;
+	}
+
+	dma_sconf.direction = DMA_DEV_TO_MEM;
+	dma_sconf.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
+	dma_sconf.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
+	dma_sconf.src_addr = res->start + SUN4I_RXDATA_REG;
+	dma_sconf.src_maxburst = 1;
+	dma_sconf.dst_maxburst = 1;
+
+	ret = dmaengine_slave_config(master->dma_rx, &dma_sconf);
+	if (ret) {
+		dev_err(dev, "Unable to configure DMA RX slave\n");
+		goto err_rel_rx;
+	}
+
+	/* don't set can_dma unless both channels are valid*/
+	master->can_dma = sun4i_spi_can_dma;
+
+	return 0;
+
+err_rel_rx:
+	dma_release_channel(master->dma_rx);
+err_rel_tx:
+	dma_release_channel(master->dma_tx);
+out:
+	master->dma_tx = NULL;
+	master->dma_rx = NULL;
+	return ret;
+}
+
+static void sun4i_spi_dma_release(struct spi_master *master)
+{
+	if (master->can_dma) {
+		dma_release_channel(master->dma_rx);
+		dma_release_channel(master->dma_tx);
+	}
+}
+
 static int sun4i_spi_probe(struct platform_device *pdev)
 {
 	struct spi_master *master;
@@ -484,6 +724,16 @@ static int sun4i_spi_probe(struct platform_device *pdev)
 		goto err_free_master;
 	}
 
+	ret = sun4i_spi_dma_setup(&pdev->dev, res);
+	if (ret) {
+		if (ret == -EPROBE_DEFER) {
+			/* wait for the dma driver to load */
+			goto err_free_master;
+		}
+		dev_warn(&pdev->dev,
+			"Unable to setup DMA channels: DMA transfers disabled\n");
+	}
+
 	/*
 	 * This wake-up/shutdown pattern is to be able to have the
 	 * device woken up, even if runtime_pm is disabled
@@ -500,7 +750,7 @@ static int sun4i_spi_probe(struct platform_device *pdev)
 
 	ret = devm_spi_register_master(&pdev->dev, master);
 	if (ret) {
-		dev_err(&pdev->dev, "cannot register SPI master\n");
+		dev_err(&pdev->dev, "Couldn't register SPI master\n");
 		goto err_pm_disable;
 	}
 
@@ -510,14 +760,19 @@ err_pm_disable:
 	pm_runtime_disable(&pdev->dev);
 	sun4i_spi_runtime_suspend(&pdev->dev);
 err_free_master:
+	sun4i_spi_dma_release(master);
 	spi_master_put(master);
 	return ret;
 }
 
 static int sun4i_spi_remove(struct platform_device *pdev)
 {
+	struct spi_master *master = platform_get_drvdata(pdev);
+
 	pm_runtime_force_suspend(&pdev->dev);
 
+	sun4i_spi_dma_release(master);
+
 	return 0;
 }
 
-- 
2.16.2

Re: [PATCH v2 1/6] spi: core: handle timeout error from transfer_one()

[Mark Brown]

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On Tue, Apr 03, 2018 at 06:29:00PM +0300, Sergey Suloev wrote:
> As long as sun4i/sun6i SPI drivers have overriden the default
> "wait for completion" procedure then we need to properly
> handle -ETIMEDOUT error from transfer_one().

Why is this connected to those drivers specifically?

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Re: [PATCH v2 1/6] spi: core: handle timeout error from transfer_one()

[Sergey Suloev]

On 04/03/2018 06:52 PM, Mark Brown wrote:
> On Tue, Apr 03, 2018 at 06:29:00PM +0300, Sergey Suloev wrote:
>> As long as sun4i/sun6i SPI drivers have overriden the default
>> "wait for completion" procedure then we need to properly
>> handle -ETIMEDOUT error from transfer_one().
> Why is this connected to those drivers specifically?

These 2 drivers have their own "waiting" code and not using the code 
from SPI core.

Re: [PATCH v2 1/6] spi: core: handle timeout error from transfer_one()

[Mark Brown]

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On Tue, Apr 03, 2018 at 07:00:55PM +0300, Sergey Suloev wrote:
> On 04/03/2018 06:52 PM, Mark Brown wrote:
> > On Tue, Apr 03, 2018 at 06:29:00PM +0300, Sergey Suloev wrote:
> > > As long as sun4i/sun6i SPI drivers have overriden the default
> > > "wait for completion" procedure then we need to properly
> > > handle -ETIMEDOUT error from transfer_one().

> > Why is this connected to those drivers specifically?

> These 2 drivers have their own "waiting" code and not using the code from
> SPI core.

Does this not apply to any other driver - why is this something we only
have to do when these drivers do it?  That's what's setting off alarm
bells.

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Re: [PATCH v2 1/6] spi: core: handle timeout error from transfer_one()

[Sergey Suloev]

On 04/03/2018 07:18 PM, Mark Brown wrote:
> On Tue, Apr 03, 2018 at 07:00:55PM +0300, Sergey Suloev wrote:
>> On 04/03/2018 06:52 PM, Mark Brown wrote:
>>> On Tue, Apr 03, 2018 at 06:29:00PM +0300, Sergey Suloev wrote:
>>>> As long as sun4i/sun6i SPI drivers have overriden the default
>>>> "wait for completion" procedure then we need to properly
>>>> handle -ETIMEDOUT error from transfer_one().
>>> Why is this connected to those drivers specifically?
>> These 2 drivers have their own "waiting" code and not using the code from
>> SPI core.
> Does this not apply to any other driver - why is this something we only
> have to do when these drivers do it?  That's what's setting off alarm
> bells.

sun4i/sun6i drivers have let's say "smart" waiting while SPI core uses a 
fixed interval to wait.

I can't say for every SPI driver in kernel, that's outside of my area of 
expertise.

Re: [PATCH v2 1/6] spi: core: handle timeout error from transfer_one()

[Maxime Ripard]

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On Tue, Apr 03, 2018 at 07:24:11PM +0300, Sergey Suloev wrote:
> On 04/03/2018 07:18 PM, Mark Brown wrote:
> > On Tue, Apr 03, 2018 at 07:00:55PM +0300, Sergey Suloev wrote:
> > > On 04/03/2018 06:52 PM, Mark Brown wrote:
> > > > On Tue, Apr 03, 2018 at 06:29:00PM +0300, Sergey Suloev wrote:
> > > > > As long as sun4i/sun6i SPI drivers have overriden the default
> > > > > "wait for completion" procedure then we need to properly
> > > > > handle -ETIMEDOUT error from transfer_one().
> > > > Why is this connected to those drivers specifically?
> > > These 2 drivers have their own "waiting" code and not using the code from
> > > SPI core.
> > Does this not apply to any other driver - why is this something we only
> > have to do when these drivers do it?  That's what's setting off alarm
> > bells.
> 
> sun4i/sun6i drivers have let's say "smart" waiting while SPI core uses a
> fixed interval to wait.
> 
> I can't say for every SPI driver in kernel, that's outside of my area of
> expertise.

I'm not sure what's specific about the sun4i / sun6i case here. Your
patch doesn't have anything to do with the delay before the timeout,
but the fact that we return -ETIMEDOUT in the first place.

And I'm pretty sure that papering over an error returned by a driver
is not the right thing to do.

Maxime

-- 
Maxime Ripard, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com

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Re: [PATCH v2 2/6] spi: sun4i: restrict transfer length in PIO-mode

[Maxime Ripard]

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On Tue, Apr 03, 2018 at 06:29:01PM +0300, Sergey Suloev wrote:
> There is no need to handle the 3/4 FIFO empty interrupt
> as the maximum supported transfer length in PIO mode
> is 64 bytes.
> As long as a problem was reported previously with filling FIFO
> on A10s we want to stick with 63 bytes depth.
> 
> Changes in v2:
> 1) Restored processing of 3/4 FIFO full interrupt.
> 
> Signed-off-by: Sergey Suloev <ssuloev@orpaltech.com>
> ---
>  drivers/spi/spi-sun4i.c | 37 ++++++++++---------------------------
>  1 file changed, 10 insertions(+), 27 deletions(-)
> 
> diff --git a/drivers/spi/spi-sun4i.c b/drivers/spi/spi-sun4i.c
> index 4141003..08fd007 100644
> --- a/drivers/spi/spi-sun4i.c
> +++ b/drivers/spi/spi-sun4i.c
> @@ -22,7 +22,12 @@
>  
>  #include <linux/spi/spi.h>
>  
> -#define SUN4I_FIFO_DEPTH		64
> +/*
> + * FIFO length is 64 bytes
> + * But filling the FIFO fully might cause a timeout
> + * on some devices, for example on spi2 on A10s
> + */
> +#define SUN4I_FIFO_DEPTH		63

The FIFO depth is 64 bytes, so the code should remain the same at
least from that regard.

>  #define SUN4I_RXDATA_REG		0x00
>  
> @@ -202,7 +207,7 @@ static void sun4i_spi_set_cs(struct spi_device *spi, bool enable)
>  
>  static size_t sun4i_spi_max_transfer_size(struct spi_device *spi)
>  {
> -	return SUN4I_FIFO_DEPTH - 1;
> +	return SUN4I_FIFO_DEPTH;
>  }
>  
>  static int sun4i_spi_transfer_one(struct spi_master *master,
> @@ -216,11 +221,8 @@ static int sun4i_spi_transfer_one(struct spi_master *master,
>  	int ret = 0;
>  	u32 reg;
>  
> -	/* We don't support transfer larger than the FIFO */
> -	if (tfr->len > SUN4I_MAX_XFER_SIZE)
> -		return -EMSGSIZE;
> -
> -	if (tfr->tx_buf && tfr->len >= SUN4I_MAX_XFER_SIZE)
> +	/* We don't support transfers larger than FIFO depth */
> +	if (tfr->len > SUN4I_FIFO_DEPTH)
>  		return -EMSGSIZE;

This essentially reverts 196737912da5, why?

Maxime

-- 
Maxime Ripard, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com

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Re: [PATCH v2 3/6] spi: sun4i: coding style/readability improvements

[Maxime Ripard]

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On Tue, Apr 03, 2018 at 06:29:02PM +0300, Sergey Suloev wrote:
> Minor changes to fulfill the coding style and
> improve the readability.

Again, this is a very subjective statement. Overall, I'm not convinced
by the idea of moving code around and shuffling variables assignments
just for the sake of it.

Maxime

-- 
Maxime Ripard, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com

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Re: [PATCH v2 4/6] spi: sun4i: use completion provided by SPI core driver

[Maxime Ripard]

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On Tue, Apr 03, 2018 at 06:29:03PM +0300, Sergey Suloev wrote:
> As long as the completion already provided by the SPI core
> then there is no need to waste extra-memory on this.
> Also a waiting function was added to avoid code duplication.

This should also be split in two parts.

Maxime

-- 
Maxime Ripard, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com

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Re: [PATCH v2 5/6] spi: sun4i: introduce register set/unset helpers

[Maxime Ripard]

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On Tue, Apr 03, 2018 at 06:29:04PM +0300, Sergey Suloev wrote:
> Two helper functions were added in order to set/unset
> specified flags in registers.

Again, the diffstat is pretty neutral, so what is the benefit?

Maxime

-- 
Maxime Ripard, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com

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Re: [PATCH v2 1/6] spi: core: handle timeout error from transfer_one()

[Mark Brown]

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On Wed, Apr 04, 2018 at 09:08:18AM +0200, Maxime Ripard wrote:

> And I'm pretty sure that papering over an error returned by a driver
> is not the right thing to do.

We've got specific error handling for timeouts - they get accounted for
separately in the stats.  It *shouldn't* affect actual operation and
AFAICT it doesn't.  I think the main problem here is that the commit
message is very unclear.

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Re: [PATCH v2 1/6] spi: core: handle timeout error from transfer_one()

[Sergey Suloev]

On 04/04/2018 10:08 AM, Maxime Ripard wrote:
> On Tue, Apr 03, 2018 at 07:24:11PM +0300, Sergey Suloev wrote:
>> On 04/03/2018 07:18 PM, Mark Brown wrote:
>>> On Tue, Apr 03, 2018 at 07:00:55PM +0300, Sergey Suloev wrote:
>>>> On 04/03/2018 06:52 PM, Mark Brown wrote:
>>>>> On Tue, Apr 03, 2018 at 06:29:00PM +0300, Sergey Suloev wrote:
>>>>>> As long as sun4i/sun6i SPI drivers have overriden the default
>>>>>> "wait for completion" procedure then we need to properly
>>>>>> handle -ETIMEDOUT error from transfer_one().
>>>>> Why is this connected to those drivers specifically?
>>>> These 2 drivers have their own "waiting" code and not using the code from
>>>> SPI core.
>>> Does this not apply to any other driver - why is this something we only
>>> have to do when these drivers do it?  That's what's setting off alarm
>>> bells.
>> sun4i/sun6i drivers have let's say "smart" waiting while SPI core uses a
>> fixed interval to wait.
>>
>> I can't say for every SPI driver in kernel, that's outside of my area of
>> expertise.
> I'm not sure what's specific about the sun4i / sun6i case here. Your
> patch doesn't have anything to do with the delay before the timeout,
> but the fact that we return -ETIMEDOUT in the first place.
>
> And I'm pretty sure that papering over an error returned by a driver
> is not the right thing to do.
>
> Maxime
>
>
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

do you mean the changes in spi.c are not required at all ?

My point was to eat ETIMEDOUT error from transfer_one() as it is just a 
mark and

shouldn't be handled as a normal error.