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Groups > linux.kernel > #1260179

[PATCH v3 2/7] spi: imx: replace fixed timeout with calculated one

From Anton Bondarenko <anton.bondarenko.sama@gmail.com>
Newsgroups linux.kernel
Subject [PATCH v3 2/7] spi: imx: replace fixed timeout with calculated one
Date 2015-11-01 15:50 +0100
Message-ID <qq27g-166-15@gated-at.bofh.it> (permalink)
References <qq27f-166-1@gated-at.bofh.it>
Organization linux.* mail to news gateway

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From: Anton Bondarenko <anton_bondarenko@mentor.com>

Fixed timeout value can fire while transaction is ongoing. This may happen
because there are no strict requirements on SPI transaction duration.
Dynamic timeout value is generated based on SCLK and transaction size.

There is also 4 * SCLK delay between TX bursts related to CS change.

Signed-off-by: Anton Bondarenko <anton_bondarenko@mentor.com>
---
 drivers/spi/spi-imx.c | 49 +++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 41 insertions(+), 8 deletions(-)

diff --git a/drivers/spi/spi-imx.c b/drivers/spi/spi-imx.c
index bd7b721..9b80c7f 100644
--- a/drivers/spi/spi-imx.c
+++ b/drivers/spi/spi-imx.c
@@ -57,7 +57,6 @@
 
 /* The maximum  bytes that a sdma BD can transfer.*/
 #define MAX_SDMA_BD_BYTES  (1 << 15)
-#define IMX_DMA_TIMEOUT (msecs_to_jiffies(3000))
 struct spi_imx_config {
 	unsigned int speed_hz;
 	unsigned int bpw;
@@ -93,6 +92,7 @@ struct spi_imx_data {
 	struct clk *clk_per;
 	struct clk *clk_ipg;
 	unsigned long spi_clk;
+	unsigned int spi_bus_clk;
 
 	unsigned int count;
 	void (*tx)(struct spi_imx_data *);
@@ -314,8 +314,7 @@ static int __maybe_unused mx51_ecspi_config(struct spi_imx_data *spi_imx,
 {
 	u32 ctrl = MX51_ECSPI_CTRL_ENABLE, dma = 0;
 	u32 cfg = readl(spi_imx->base + MX51_ECSPI_CONFIG);
-
-	u32 clk = config->speed_hz, delay;
+	u32 delay;
 
 	/*
 	 * The hardware seems to have a race condition when changing modes. The
@@ -327,7 +326,9 @@ static int __maybe_unused mx51_ecspi_config(struct spi_imx_data *spi_imx,
 	ctrl |= MX51_ECSPI_CTRL_MODE_MASK;
 
 	/* set clock speed */
-	ctrl |= mx51_ecspi_clkdiv(spi_imx->spi_clk, config->speed_hz, &clk);
+	spi_imx->spi_bus_clk = config->speed_hz;
+	ctrl |= mx51_ecspi_clkdiv(spi_imx->spi_clk, config->speed_hz,
+				  &spi_imx->spi_bus_clk);
 
 	/* set chip select to use */
 	ctrl |= MX51_ECSPI_CTRL_CS(config->cs);
@@ -367,7 +368,7 @@ static int __maybe_unused mx51_ecspi_config(struct spi_imx_data *spi_imx,
 	 * the SPI communication as the device on the other end would consider
 	 * the change of SCLK polarity as a clock tick already.
 	 */
-	delay = (2 * 1000000) / clk;
+	delay = (2 * USEC_PER_SEC) / spi_imx->spi_bus_clk;
 	if (likely(delay < 10))	/* SCLK is faster than 100 kHz */
 		udelay(delay);
 	else			/* SCLK is _very_ slow */
@@ -890,12 +891,40 @@ static void spi_imx_dma_tx_callback(void *cookie)
 	complete(&spi_imx->dma_tx_completion);
 }
 
+static int spi_imx_calculate_timeout(struct spi_imx_data *spi_imx, int size)
+{
+	unsigned long coef1 = 1;
+	unsigned long coef2 = MSEC_PER_SEC;
+	unsigned long timeout = 0;
+
+	/* Swap coeficients to avoid div by 0 */
+	if (spi_imx->spi_bus_clk < MSEC_PER_SEC) {
+		coef1 = MSEC_PER_SEC;
+		coef2 = 1;
+	}
+
+	/* Time with actual data transfer */
+	timeout += DIV_ROUND_UP(8 * size * coef1,
+				spi_imx->spi_bus_clk / coef2);
+
+	/* Take CS change delay related to HW */
+	timeout += DIV_ROUND_UP((size - 1) * 4 * coef1,
+				spi_imx->spi_bus_clk / coef2);
+
+	/* Add extra second for scheduler related activities */
+	timeout += MSEC_PER_SEC;
+
+	/* Double calculated timeout */
+	return msecs_to_jiffies(2 * timeout);
+}
+
 static int spi_imx_dma_transfer(struct spi_imx_data *spi_imx,
 				struct spi_transfer *transfer)
 {
 	struct dma_async_tx_descriptor *desc_tx = NULL, *desc_rx = NULL;
 	int ret;
 	unsigned long timeout;
+	unsigned long transfer_timeout;
 	const int left = transfer->len % spi_imx->wml;
 	struct spi_master *master = spi_imx->bitbang.master;
 	struct sg_table *tx = &transfer->tx_sg, *rx = &transfer->rx_sg;
@@ -956,9 +985,11 @@ static int spi_imx_dma_transfer(struct spi_imx_data *spi_imx,
 	dma_async_issue_pending(master->dma_tx);
 	spi_imx->devtype_data->trigger(spi_imx);
 
+	transfer_timeout = spi_imx_calculate_timeout(spi_imx, transfer->len);
+
 	/* Wait SDMA to finish the data transfer.*/
 	timeout = wait_for_completion_timeout(&spi_imx->dma_tx_completion,
-						IMX_DMA_TIMEOUT);
+						transfer_timeout);
 	if (!timeout) {
 		pr_warn("%s %s: I/O Error in DMA TX\n",
 			dev_driver_string(&master->dev),
@@ -966,8 +997,10 @@ static int spi_imx_dma_transfer(struct spi_imx_data *spi_imx,
 		dmaengine_terminate_all(master->dma_tx);
 		dmaengine_terminate_all(master->dma_rx);
 	} else {
+		transfer_timeout = spi_imx_calculate_timeout(spi_imx,
+							     spi_imx->wml);
 		timeout = wait_for_completion_timeout(
-				&spi_imx->dma_rx_completion, IMX_DMA_TIMEOUT);
+				&spi_imx->dma_rx_completion, transfer_timeout);
 		if (!timeout) {
 			pr_warn("%s %s: I/O Error in DMA RX\n",
 				dev_driver_string(&master->dev),
@@ -989,7 +1022,7 @@ static int spi_imx_dma_transfer(struct spi_imx_data *spi_imx,
 			spi_imx->devtype_data->intctrl(spi_imx, MXC_INT_TCEN);
 
 			timeout = wait_for_completion_timeout(
-					&spi_imx->xfer_done, IMX_DMA_TIMEOUT);
+					&spi_imx->xfer_done, transfer_timeout);
 			if (!timeout) {
 				pr_warn("%s %s: I/O Error in RX tail\n",
 					dev_driver_string(&master->dev),
-- 
2.6.2

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[PATCH v3 0/7] Improvements for SPI IMX driver for Freescale IMX51, IMX53 and IMX6 Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-11-01 15:50 +0100
  [PATCH v3 5/7] spi: imx: Add support for loopback for ECSPI controllers Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-11-01 15:50 +0100
    Re: [PATCH v3 5/7] spi: imx: Add support for loopback for ECSPI  controllers Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-11-14 11:10 +0100
  [PATCH v3 6/7] spi: imx: return error from dma channel request Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-11-01 15:50 +0100
    Re: [PATCH v3 6/7] spi: imx: return error from dma channel request Sascha Hauer <s.hauer@pengutronix.de> - 2015-11-05 10:00 +0100
      Re: [PATCH v3 6/7] spi: imx: return error from dma channel request Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-11-05 17:10 +0100
        Re: [PATCH v3 6/7] spi: imx: return error from dma channel request Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-11-14 11:10 +0100
        Re: [PATCH v3 6/7] spi: imx: return error from dma channel request Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-11-14 11:10 +0100
  [PATCH v3 4/7] spi: imx: add function to check for IMX51 family controller Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-11-01 15:50 +0100
    Re: [PATCH v3 4/7] spi: imx: add function to check for IMX51 family  controller Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-11-14 11:10 +0100
  [PATCH v3 3/7] spi: imx: add support for all SPI word width for DMA transfer Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-11-01 15:50 +0100
  [PATCH v3 1/7] spi: imx: Fix DMA transfer Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-11-01 15:50 +0100
    Re: [PATCH v3 1/7] spi: imx: Fix DMA transfer Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-11-04 22:10 +0100
    Re: [PATCH v3 1/7] spi: imx: Fix DMA transfer Sascha Hauer <s.hauer@pengutronix.de> - 2015-11-05 09:40 +0100
      Re: [PATCH v3 1/7] spi: imx: Fix DMA transfer Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-11-05 18:00 +0100
        Re: [PATCH v3 1/7] spi: imx: Fix DMA transfer Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-11-14 11:10 +0100
  [PATCH v3 7/7] spi: imx: defer spi initialization, if DMA engine is pending Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-11-01 15:50 +0100
    Re: [PATCH v3 7/7] spi: imx: defer spi initialization, if DMA engine  is pending Sascha Hauer <s.hauer@pengutronix.de> - 2015-11-05 10:00 +0100
      Re: [PATCH v3 7/7] spi: imx: defer spi initialization, if DMA engine  is pending Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-11-05 17:20 +0100
        Re: [PATCH v3 7/7] spi: imx: defer spi initialization, if DMA engine  is pending Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-11-14 11:10 +0100
  [PATCH v3 2/7] spi: imx: replace fixed timeout with calculated one Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-11-01 15:50 +0100
    Re: [PATCH v3 2/7] spi: imx: replace fixed timeout with calculated  one Sascha Hauer <s.hauer@pengutronix.de> - 2015-11-05 09:50 +0100
      Re: [PATCH v3 2/7] spi: imx: replace fixed timeout with calculated  one Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-11-10 21:30 +0100
        Re: [PATCH v3 2/7] spi: imx: replace fixed timeout with calculated  one Sascha Hauer <s.hauer@pengutronix.de> - 2015-11-11 09:20 +0100
          Re: [PATCH v3 2/7] spi: imx: replace fixed timeout with calculated  one Anton Bondarenko <anton.bondarenko.sama@gmail.com> - 2015-11-14 11:10 +0100

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