trunk-47381HEADmaster

1 files changed, 136 insertions, 0 deletions

diff --git a/target/linux/brcm2708/patches-4.1/0155-spi-bcm2835-fallback-to-interrupt-for-polling-timeou.patch b/target/linux/brcm2708/patches-4.1/0155-spi-bcm2835-fallback-to-interrupt-for-polling-timeou.patch
new file mode 100644
index 0000000..766923e
--- /dev/null
+++ b/target/linux/brcm2708/patches-4.1/0155-spi-bcm2835-fallback-to-interrupt-for-polling-timeou.patch
@@ -0,0 +1,136 @@
+From 0e646de6b27ee8b6631e5cebf8beffeccad8de63 Mon Sep 17 00:00:00 2001
+From: Martin Sperl <kernel@martin.sperl.org>
+Date: Wed, 22 Apr 2015 07:33:03 +0000
+Subject: [PATCH 155/203] spi: bcm2835: fallback to interrupt for polling
+ timeouts exceeding 2 jiffies
+
+The polling mode of the driver is designed for transfers that run
+less than 30us - it will only execute under those circumstances.
+So it should run comfortably without getting interrupted by the
+scheduler.
+
+But there are situations where the raspberry pi is so overloaded
+that it can take up to 80 jiffies until the polling thread gets
+rescheduled - this has been observed especially under heavy
+IO situations.
+
+In such a situation we now fall back to the interrupt handler and
+log the situation at debug level.
+
+Signed-off-by: Martin Sperl <kernel@martin.sperl.org>
+Signed-off-by: Mark Brown <broonie@kernel.org>
+(cherry picked from commit a750b124cfd27bae1a12df22318db5a2083dfb12)
+---
+ drivers/spi/spi-bcm2835.c | 87 +++++++++++++++++++++++++++--------------------
+ 1 file changed, 50 insertions(+), 37 deletions(-)
+
+--- a/drivers/spi/spi-bcm2835.c
++++ b/drivers/spi/spi-bcm2835.c
+@@ -69,7 +69,7 @@
+ #define BCM2835_SPI_CS_CS_01		0x00000001
+ 
+ #define BCM2835_SPI_POLLING_LIMIT_US	30
+-#define BCM2835_SPI_TIMEOUT_MS		30000
++#define BCM2835_SPI_POLLING_JIFFIES	2
+ #define BCM2835_SPI_MODE_BITS	(SPI_CPOL | SPI_CPHA | SPI_CS_HIGH \
+ 				| SPI_NO_CS | SPI_3WIRE)
+ 
+@@ -157,42 +157,6 @@ static irqreturn_t bcm2835_spi_interrupt
+ 	return IRQ_HANDLED;
+ }
+ 
+-static int bcm2835_spi_transfer_one_poll(struct spi_master *master,
+-					 struct spi_device *spi,
+-					 struct spi_transfer *tfr,
+-					 u32 cs,
+-					 unsigned long xfer_time_us)
+-{
+-	struct bcm2835_spi *bs = spi_master_get_devdata(master);
+-	/* set timeout to 1 second of maximum polling */
+-	unsigned long timeout = jiffies + HZ;
+-
+-	/* enable HW block without interrupts */
+-	bcm2835_wr(bs, BCM2835_SPI_CS, cs | BCM2835_SPI_CS_TA);
+-
+-	/* loop until finished the transfer */
+-	while (bs->rx_len) {
+-		/* read from fifo as much as possible */
+-		bcm2835_rd_fifo(bs);
+-		/* fill in tx fifo as much as possible */
+-		bcm2835_wr_fifo(bs);
+-		/* if we still expect some data after the read,
+-		 * check for a possible timeout
+-		 */
+-		if (bs->rx_len && time_after(jiffies, timeout)) {
+-			/* Transfer complete - reset SPI HW */
+-			bcm2835_spi_reset_hw(master);
+-			/* and return timeout */
+-			return -ETIMEDOUT;
+-		}
+-	}
+-
+-	/* Transfer complete - reset SPI HW */
+-	bcm2835_spi_reset_hw(master);
+-	/* and return without waiting for completion */
+-	return 0;
+-}
+-
+ static int bcm2835_spi_transfer_one_irq(struct spi_master *master,
+ 					struct spi_device *spi,
+ 					struct spi_transfer *tfr,
+@@ -229,6 +193,55 @@ static int bcm2835_spi_transfer_one_irq(
+ 	return 1;
+ }
+ 
++static int bcm2835_spi_transfer_one_poll(struct spi_master *master,
++					 struct spi_device *spi,
++					 struct spi_transfer *tfr,
++					 u32 cs,
++					 unsigned long xfer_time_us)
++{
++	struct bcm2835_spi *bs = spi_master_get_devdata(master);
++	unsigned long timeout;
++
++	/* enable HW block without interrupts */
++	bcm2835_wr(bs, BCM2835_SPI_CS, cs | BCM2835_SPI_CS_TA);
++
++	/* fill in the fifo before timeout calculations
++	 * if we are interrupted here, then the data is
++	 * getting transferred by the HW while we are interrupted
++	 */
++	bcm2835_wr_fifo(bs);
++
++	/* set the timeout */
++	timeout = jiffies + BCM2835_SPI_POLLING_JIFFIES;
++
++	/* loop until finished the transfer */
++	while (bs->rx_len) {
++		/* fill in tx fifo with remaining data */
++		bcm2835_wr_fifo(bs);
++
++		/* read from fifo as much as possible */
++		bcm2835_rd_fifo(bs);
++
++		/* if there is still data pending to read
++		 * then check the timeout
++		 */
++		if (bs->rx_len && time_after(jiffies, timeout)) {
++			dev_dbg_ratelimited(&spi->dev,
++					    "timeout period reached: jiffies: %lu remaining tx/rx: %d/%d - falling back to interrupt mode\n",
++					    jiffies - timeout,
++					    bs->tx_len, bs->rx_len);
++			/* fall back to interrupt mode */
++			return bcm2835_spi_transfer_one_irq(master, spi,
++							    tfr, cs);
++		}
++	}
++
++	/* Transfer complete - reset SPI HW */
++	bcm2835_spi_reset_hw(master);
++	/* and return without waiting for completion */
++	return 0;
++}
++
+ static int bcm2835_spi_transfer_one(struct spi_master *master,
+ 				    struct spi_device *spi,
+ 				    struct spi_transfer *tfr)