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From: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
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Date: Thu, 3 Sep 2009 07:59:01 -0600
Subject: [PATCH 2/2] spi_txx9: Fix bit rate calculation
Thread-Topic: [PATCH 2/2] spi_txx9: Fix bit rate calculation
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TXx9 SPI bit rate is calculated by:
        fBR =3D (spi-baseclk) / (n + 1)
Fix calculation of min_speed_hz, max_speed_hz and n.

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
---
 drivers/spi/spi_txx9.c |   13 ++++++-------
 1 files changed, 6 insertions(+), 7 deletions(-)

diff --git a/drivers/spi/spi_txx9.c b/drivers/spi/spi_txx9.c
index 96057de..19f7562 100644
--- a/drivers/spi/spi_txx9.c
+++ b/drivers/spi/spi_txx9.c
@@ -29,6 +29,8 @@
=20
=20
 #define SPI_FIFO_SIZE 4
+#define SPI_MAX_DIVIDER 0xff	/* Max. value for SPCR1.SER */
+#define SPI_MIN_DIVIDER 1	/* Min. value for SPCR1.SER */
=20
 #define TXx9_SPMCR		0x00
 #define TXx9_SPCR0		0x04
@@ -193,11 +195,8 @@ static void txx9spi_work_one(struct txx9spi *c, struct=
 spi_message *m)
=20
 		if (prev_speed_hz !=3D speed_hz
 				|| prev_bits_per_word !=3D bits_per_word) {
-			u32 n =3D (c->baseclk + speed_hz - 1) / speed_hz;
-			if (n < 1)
-				n =3D 1;
-			else if (n > 0xff)
-				n =3D 0xff;
+			int n =3D DIV_ROUND_UP(c->baseclk, speed_hz) - 1;
+			n =3D clamp(n, SPI_MIN_DIVIDER, SPI_MAX_DIVIDER);
 			/* enter config mode */
 			txx9spi_wr(c, mcr | TXx9_SPMCR_CONFIG | TXx9_SPMCR_BCLR,
 					TXx9_SPMCR);
@@ -370,8 +369,8 @@ static int __init txx9spi_probe(struct platform_device =
*dev)
 		goto exit;
 	}
 	c->baseclk =3D clk_get_rate(c->clk);
-	c->min_speed_hz =3D (c->baseclk + 0xff - 1) / 0xff;
-	c->max_speed_hz =3D c->baseclk;
+	c->min_speed_hz =3D DIV_ROUND_UP(c->baseclk, SPI_MAX_DIVIDER + 1);
+	c->max_speed_hz =3D c->baseclk / (SPI_MIN_DIVIDER + 1);
=20
 	res =3D platform_get_resource(dev, IORESOURCE_MEM, 0);
 	if (!res)
--=20
1.5.6.5


