From dbf763a2f1c117cfe45bbbd2c874a150f0e0900b Mon Sep 17 00:00:00 2001 From: Atsushi Nemoto Date: Thu, 3 Sep 2009 22:59:01 +0900 Subject: SPI: spi_txx9: Fix bit rate calculation TXx9 SPI bit rate is calculated by: fBR = (spi-baseclk) / (n + 1) Fix calculation of min_speed_hz, max_speed_hz and n. Signed-off-by: Atsushi Nemoto Signed-off-by: Ralf Baechle --- drivers/spi/spi_txx9.c | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-) diff --git a/drivers/spi/spi_txx9.c b/drivers/spi/spi_txx9.c index 96057de133a..19f75627c3d 100644 --- a/drivers/spi/spi_txx9.c +++ b/drivers/spi/spi_txx9.c @@ -29,6 +29,8 @@ #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 */ #define TXx9_SPMCR 0x00 #define TXx9_SPCR0 0x04 @@ -193,11 +195,8 @@ static void txx9spi_work_one(struct txx9spi *c, struct spi_message *m) if (prev_speed_hz != speed_hz || prev_bits_per_word != bits_per_word) { - u32 n = (c->baseclk + speed_hz - 1) / speed_hz; - if (n < 1) - n = 1; - else if (n > 0xff) - n = 0xff; + int n = DIV_ROUND_UP(c->baseclk, speed_hz) - 1; + n = 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 = clk_get_rate(c->clk); - c->min_speed_hz = (c->baseclk + 0xff - 1) / 0xff; - c->max_speed_hz = c->baseclk; + c->min_speed_hz = DIV_ROUND_UP(c->baseclk, SPI_MAX_DIVIDER + 1); + c->max_speed_hz = c->baseclk / (SPI_MIN_DIVIDER + 1); res = platform_get_resource(dev, IORESOURCE_MEM, 0); if (!res) -- cgit v1.2.3