diff options
| author | Atsushi Nemoto <anemo@mba.ocn.ne.jp> | 2009-09-03 22:59:01 +0900 |
|---|---|---|
| committer | Ralf Baechle <ralf@linux-mips.org> | 2009-12-02 23:58:32 +0000 |
| commit | dbf763a2f1c117cfe45bbbd2c874a150f0e0900b (patch) | |
| tree | 175d8b9c1848a0923150ef1bc4ef003a9a032d2c /drivers/spi/spi_txx9.c | |
| parent | 56f3f55cf9b604b924353ab6fcdac5fee5637ae3 (diff) | |
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 <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Diffstat (limited to 'drivers/spi/spi_txx9.c')
| -rw-r--r-- | 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 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) |