address SPI_CLKDIV_PRE requirements

* respect N-1 * avoid range overflow
2015-10-04 16:57:50 +02:00 · 2015-10-04 16:57:50 +02:00 · 4cf5f37450
parent ac50f9c6a5
commit 4cf5f37450
1 changed files with 4 additions and 1 deletions
--- a/app/driver/spi.c
+++ b/app/driver/spi.c
@ -116,6 +116,9 @@ void spi_master_init(uint8 spi_no, unsigned cpol, unsigned cpha, unsigned databi
 		clock_div += 0x02;
 	}
 	clock_div >>= 1;
+	// clip to maximum possible CLKDIV_PRE
+	clock_div = clock_div > SPI_CLKDIV_PRE ? SPI_CLKDIV_PRE : clock_div - 1;
+
 	WRITE_PERI_REG(SPI_CLOCK(spi_no), 
 					((clock_div&SPI_CLKDIV_PRE)<<SPI_CLKDIV_PRE_S)|
 					((1&SPI_CLKCNT_N)<<SPI_CLKCNT_N_S)|