kw_spi: fix clock prescaler computation
The computation was not correct with low clock values: setting a 1MHz
clock would result in an overlap that would then configure a 25Mhz
clock.
This patch implements a correct computation method according to the
kirkwood functionnal spec. table 600 (Serial Memory Interface
Configuration Register).
Signed-off-by: Valentin Longchamp <valentin.longchamp@keymile.com>
cc: Holger Brunck <holger.brunck@keymile.com>
cc: Prafulla Wadaskar <prafulla@marvell.com>
Acked-by: Prafulla Wadaskar <Prafulla@marvell.com>
Signed-off-by: Prafulla Wadaskar <prafulla@marvell.com>
diff --git a/arch/arm/include/asm/arch-kirkwood/spi.h b/arch/arm/include/asm/arch-kirkwood/spi.h
index c79bed7..113f258 100644
--- a/arch/arm/include/asm/arch-kirkwood/spi.h
+++ b/arch/arm/include/asm/arch-kirkwood/spi.h
@@ -49,6 +49,7 @@
#define MISO_MPP11 (1 << 2)
#define KWSPI_CLKPRESCL_MASK 0x1f
+#define KWSPI_CLKPRESCL_MIN 0x12
#define KWSPI_CSN_ACT 1 /* Activates serial memory interface */
#define KWSPI_SMEMRDY (1 << 1) /* SerMem Data xfer ready */
#define KWSPI_IRQUNMASK 1 /* unmask SPI interrupt */