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>
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 @@
#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 @@
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 @@
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)