d4b8d51580
As usual, this patches were taken (and rebased) from https://github.com/raspberrypi/linux/commits/rpi-4.1.y Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com> SVN-Revision: 47922
137 lines
4.3 KiB
Diff
137 lines
4.3 KiB
Diff
From 4a42130b7fe39652a3ed8ced413a71c7f5d7ce61 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 155/222] 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)
|