linux-kernel - [PATCH 4/7] spi: s3c64xx: Use jiffies instead of loops for timeout

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Date:	Tue, 18 Sep 2012 11:21:56 -0700
From:	Simon Glass <sjg@...omium.org>
To:	LKML <linux-kernel@...r.kernel.org>,
	linux-arm-kernel@...ts.infradead.org
Cc:	"kgene.kim" <kgene.kim@...sung.com>,
	Ben Dooks <ben-linux@...ff.org>,
	Srinivas KANDAGATLA <srinivas.kandagatla@...com>,
	Simon Glass <sjg@...omium.org>
Subject: [PATCH 4/7] spi: s3c64xx: Use jiffies instead of loops for timeout

The current timeout uses loops, but does not actually use an empty loop. In
fact it checks SPI registers which are pretty slow to read. As a result the
timeout ends up being several seconds most of the time.

Change this to use jiffies instead.

Signed-off-by: Simon Glass <sjg@...omium.org>
---
 drivers/spi/spi-s3c64xx.c |   37 ++++++++++++++++++++++---------------
 1 files changed, 22 insertions(+), 15 deletions(-)

diff --git a/drivers/spi/spi-s3c64xx.c b/drivers/spi/spi-s3c64xx.c
index 95a1bfc..db79d87 100644
--- a/drivers/spi/spi-s3c64xx.c
+++ b/drivers/spi/spi-s3c64xx.c
@@ -427,6 +427,7 @@ static inline void enable_cs(struct s3c64xx_spi_driver_data *sdd,
 static int wait_for_xfer(struct s3c64xx_spi_driver_data *sdd,
 				struct spi_transfer *xfer, int dma_mode)
 {
+	struct device *dev = &sdd->pdev->dev;
 	void __iomem *regs = sdd->regs;
 	unsigned long val;
 	int ms;
@@ -439,16 +440,21 @@ static int wait_for_xfer(struct s3c64xx_spi_driver_data *sdd,
 		val = msecs_to_jiffies(ms) + 10;
 		val = wait_for_completion_timeout(&sdd->xfer_completion, val);
 	} else {
+		ulong deadline;
 		u32 status;
-		val = msecs_to_loops(ms);
+
+		deadline = jiffies + msecs_to_jiffies(ms);
 		do {
 			status = readl(regs + S3C64XX_SPI_STATUS);
-		} while (RX_FIFO_LVL(status, sdd) < xfer->len && --val);
+			if (time_after(jiffies, deadline)) {
+				dev_warn(dev, "RX timeout level=%d, need=%d\n",
+					RX_FIFO_LVL(status, sdd), xfer->len);
+				return -EIO;
+			}
+			cpu_relax();
+		} while (RX_FIFO_LVL(status, sdd) < xfer->len);
 	}
 
-	if (!val)
-		return -EIO;
-
 	if (dma_mode) {
 		u32 status;
 
@@ -460,17 +466,18 @@ static int wait_for_xfer(struct s3c64xx_spi_driver_data *sdd,
 		 * Xfer involved Rx(with or without Tx).
 		 */
 		if (xfer->rx_buf == NULL) {
-			val = msecs_to_loops(10);
-			status = readl(regs + S3C64XX_SPI_STATUS);
-			while ((TX_FIFO_LVL(status, sdd)
-				|| !S3C64XX_SPI_ST_TX_DONE(status, sdd))
-					&& --val) {
-				cpu_relax();
-				status = readl(regs + S3C64XX_SPI_STATUS);
-			}
+			ulong deadline;
 
-			if (!val)
-				return -EIO;
+			deadline = jiffies + msecs_to_jiffies(10);
+			do {
+				status = readl(regs + S3C64XX_SPI_STATUS);
+				if (time_after(jiffies, deadline)) {
+					dev_warn(dev, "TX timeout level=%d\n",
+						TX_FIFO_LVL(status, sdd));
+					return -EIO;
+				}
+			} while (TX_FIFO_LVL(status, sdd) ||
+					!S3C64XX_SPI_ST_TX_DONE(status, sdd));
 		}
 	} else {
 		/* If it was only Tx */
-- 
1.7.7.3

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