From 825fc9e8e78ecc63bb933facf678367b7606d0b0 Mon Sep 17 00:00:00 2001
From: Haavard Skinnemoen <haavard.skinnemoen@atmel.com>
Date: Wed, 30 Apr 2008 00:52:17 -0700
Subject: [PATCH] --- yaml --- r: 95079 b: refs/heads/master c:
 592e7bf80566bf5ac3ed073d4e198dd5b0824c04 h: refs/heads/master i:   95077:
 26f0ff8be56d4370d6158ef97c207cac0018f878   95075:
 d0a3ca96fa3a99c77e7be9958af5f102d0cd907d   95071:
 1269bfa21b6a96a8aec5432ba5961183bd92b1af v: v3

---
 [refs]                        |  2 +-
 trunk/drivers/spi/atmel_spi.c | 29 ++++++++++++++++++++---------
 2 files changed, 21 insertions(+), 10 deletions(-)

diff --git a/[refs] b/[refs]
index d3b5dccda862..4f722497c569 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: c6495aaabfaa8256c292c54b48ab081f4d86ad79
+refs/heads/master: 592e7bf80566bf5ac3ed073d4e198dd5b0824c04
diff --git a/trunk/drivers/spi/atmel_spi.c b/trunk/drivers/spi/atmel_spi.c
index 02c8e305b14f..e81d59d78910 100644
--- a/trunk/drivers/spi/atmel_spi.c
+++ b/trunk/drivers/spi/atmel_spi.c
@@ -497,7 +497,7 @@ static int atmel_spi_setup(struct spi_device *spi)
 	struct atmel_spi	*as;
 	u32			scbr, csr;
 	unsigned int		bits = spi->bits_per_word;
-	unsigned long		bus_hz, sck_hz;
+	unsigned long		bus_hz;
 	unsigned int		npcs_pin;
 	int			ret;
 
@@ -536,14 +536,25 @@ static int atmel_spi_setup(struct spi_device *spi)
 		return -EINVAL;
 	}
 
-	/* speed zero convention is used by some upper layers */
+	/*
+	 * Pre-new_1 chips start out at half the peripheral
+	 * bus speed.
+	 */
 	bus_hz = clk_get_rate(as->clk);
+	if (!as->new_1)
+		bus_hz /= 2;
+
 	if (spi->max_speed_hz) {
-		/* assume div32/fdiv/mbz == 0 */
-		if (!as->new_1)
-			bus_hz /= 2;
-		scbr = ((bus_hz + spi->max_speed_hz - 1)
-			/ spi->max_speed_hz);
+		/*
+		 * Calculate the lowest divider that satisfies the
+		 * constraint, assuming div32/fdiv/mbz == 0.
+		 */
+		scbr = DIV_ROUND_UP(bus_hz, spi->max_speed_hz);
+
+		/*
+		 * If the resulting divider doesn't fit into the
+		 * register bitfield, we can't satisfy the constraint.
+		 */
 		if (scbr >= (1 << SPI_SCBR_SIZE)) {
 			dev_dbg(&spi->dev,
 				"setup: %d Hz too slow, scbr %u; min %ld Hz\n",
@@ -551,8 +562,8 @@ static int atmel_spi_setup(struct spi_device *spi)
 			return -EINVAL;
 		}
 	} else
+		/* speed zero means "as slow as possible" */
 		scbr = 0xff;
-	sck_hz = bus_hz / scbr;
 
 	csr = SPI_BF(SCBR, scbr) | SPI_BF(BITS, bits - 8);
 	if (spi->mode & SPI_CPOL)
@@ -589,7 +600,7 @@ static int atmel_spi_setup(struct spi_device *spi)
 
 	dev_dbg(&spi->dev,
 		"setup: %lu Hz bpw %u mode 0x%x -> csr%d %08x\n",
-		sck_hz, bits, spi->mode, spi->chip_select, csr);
+		bus_hz / scbr, bits, spi->mode, spi->chip_select, csr);
 
 	spi_writel(as, CSR0 + 4 * spi->chip_select, csr);