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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: 47258
137 lines
4.3 KiB
Diff
137 lines
4.3 KiB
Diff
From 0e646de6b27ee8b6631e5cebf8beffeccad8de63 Mon Sep 17 00:00:00 2001
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From: Martin Sperl <kernel@martin.sperl.org>
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Date: Wed, 22 Apr 2015 07:33:03 +0000
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Subject: [PATCH 155/203] spi: bcm2835: fallback to interrupt for polling
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timeouts exceeding 2 jiffies
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The polling mode of the driver is designed for transfers that run
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less than 30us - it will only execute under those circumstances.
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So it should run comfortably without getting interrupted by the
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scheduler.
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But there are situations where the raspberry pi is so overloaded
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that it can take up to 80 jiffies until the polling thread gets
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rescheduled - this has been observed especially under heavy
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IO situations.
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In such a situation we now fall back to the interrupt handler and
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log the situation at debug level.
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Signed-off-by: Martin Sperl <kernel@martin.sperl.org>
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Signed-off-by: Mark Brown <broonie@kernel.org>
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(cherry picked from commit a750b124cfd27bae1a12df22318db5a2083dfb12)
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---
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drivers/spi/spi-bcm2835.c | 87 +++++++++++++++++++++++++++--------------------
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1 file changed, 50 insertions(+), 37 deletions(-)
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--- a/drivers/spi/spi-bcm2835.c
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+++ b/drivers/spi/spi-bcm2835.c
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@@ -69,7 +69,7 @@
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#define BCM2835_SPI_CS_CS_01 0x00000001
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#define BCM2835_SPI_POLLING_LIMIT_US 30
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-#define BCM2835_SPI_TIMEOUT_MS 30000
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+#define BCM2835_SPI_POLLING_JIFFIES 2
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#define BCM2835_SPI_MODE_BITS (SPI_CPOL | SPI_CPHA | SPI_CS_HIGH \
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| SPI_NO_CS | SPI_3WIRE)
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@@ -157,42 +157,6 @@ static irqreturn_t bcm2835_spi_interrupt
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return IRQ_HANDLED;
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}
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-static int bcm2835_spi_transfer_one_poll(struct spi_master *master,
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- struct spi_device *spi,
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- struct spi_transfer *tfr,
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- u32 cs,
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- unsigned long xfer_time_us)
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-{
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- struct bcm2835_spi *bs = spi_master_get_devdata(master);
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- /* set timeout to 1 second of maximum polling */
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- unsigned long timeout = jiffies + HZ;
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-
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- /* enable HW block without interrupts */
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- bcm2835_wr(bs, BCM2835_SPI_CS, cs | BCM2835_SPI_CS_TA);
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-
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- /* loop until finished the transfer */
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- while (bs->rx_len) {
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- /* read from fifo as much as possible */
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- bcm2835_rd_fifo(bs);
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- /* fill in tx fifo as much as possible */
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- bcm2835_wr_fifo(bs);
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- /* if we still expect some data after the read,
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- * check for a possible timeout
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- */
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- if (bs->rx_len && time_after(jiffies, timeout)) {
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- /* Transfer complete - reset SPI HW */
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- bcm2835_spi_reset_hw(master);
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- /* and return timeout */
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- return -ETIMEDOUT;
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- }
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- }
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-
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- /* Transfer complete - reset SPI HW */
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- bcm2835_spi_reset_hw(master);
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- /* and return without waiting for completion */
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- return 0;
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-}
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-
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static int bcm2835_spi_transfer_one_irq(struct spi_master *master,
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struct spi_device *spi,
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struct spi_transfer *tfr,
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@@ -229,6 +193,55 @@ static int bcm2835_spi_transfer_one_irq(
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return 1;
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}
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+static int bcm2835_spi_transfer_one_poll(struct spi_master *master,
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+ struct spi_device *spi,
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+ struct spi_transfer *tfr,
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+ u32 cs,
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+ unsigned long xfer_time_us)
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+{
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+ struct bcm2835_spi *bs = spi_master_get_devdata(master);
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+ unsigned long timeout;
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+
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+ /* enable HW block without interrupts */
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+ bcm2835_wr(bs, BCM2835_SPI_CS, cs | BCM2835_SPI_CS_TA);
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+
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+ /* fill in the fifo before timeout calculations
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+ * if we are interrupted here, then the data is
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+ * getting transferred by the HW while we are interrupted
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+ */
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+ bcm2835_wr_fifo(bs);
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+
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+ /* set the timeout */
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+ timeout = jiffies + BCM2835_SPI_POLLING_JIFFIES;
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+
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+ /* loop until finished the transfer */
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+ while (bs->rx_len) {
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+ /* fill in tx fifo with remaining data */
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+ bcm2835_wr_fifo(bs);
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+
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+ /* read from fifo as much as possible */
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+ bcm2835_rd_fifo(bs);
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+
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+ /* if there is still data pending to read
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+ * then check the timeout
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+ */
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+ if (bs->rx_len && time_after(jiffies, timeout)) {
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+ dev_dbg_ratelimited(&spi->dev,
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+ "timeout period reached: jiffies: %lu remaining tx/rx: %d/%d - falling back to interrupt mode\n",
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+ jiffies - timeout,
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+ bs->tx_len, bs->rx_len);
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+ /* fall back to interrupt mode */
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+ return bcm2835_spi_transfer_one_irq(master, spi,
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+ tfr, cs);
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+ }
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+ }
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+
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+ /* Transfer complete - reset SPI HW */
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+ bcm2835_spi_reset_hw(master);
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+ /* and return without waiting for completion */
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+ return 0;
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+}
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+
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static int bcm2835_spi_transfer_one(struct spi_master *master,
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struct spi_device *spi,
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struct spi_transfer *tfr)
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