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 629 (Serial Memory Interface
Configuration Register).
Signed-off-by: Valentin Longchamp <valentin.longch...@keymile.com>
cc: Holger Brunck <holger.bru...@keymile.com>
cc: Prafulla Wadaskar <prafu...@marvell.com>
---
arch/arm/include/asm/arch-kirkwood/spi.h | 1 +
drivers/spi/kirkwood_spi.c | 5 +++--
2 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/arch/arm/include/asm/arch-kirkwood/spi.h
b/arch/arm/include/asm/arch-kirkwood/spi.h
index 1d5043f..5a38dc5 100644
--- a/arch/arm/include/asm/arch-kirkwood/spi.h
+++ b/arch/arm/include/asm/arch-kirkwood/spi.h
@@ -38,6 +38,7 @@ struct kwspi_registers {
};
#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 */
diff --git a/drivers/spi/kirkwood_spi.c b/drivers/spi/kirkwood_spi.c
index ee14669..9b3f6a4 100644
--- a/drivers/spi/kirkwood_spi.c
+++ b/drivers/spi/kirkwood_spi.c
@@ -57,8 +57,9 @@ struct spi_slave *spi_setup_slave(unsigned int bus, unsigned
int cs,
writel(~KWSPI_CSN_ACT | KWSPI_SMEMRDY, &spireg->ctrl);
/* calculate spi clock prescaller using max_hz */
- data = ((CONFIG_SYS_TCLK / 2) / max_hz) & KWSPI_CLKPRESCL_MASK;
- data |= 0x10;
+ data = ((CONFIG_SYS_TCLK / 2) / max_hz) + 0x10;
+ data = data < KWSPI_CLKPRESCL_MIN ? KWSPI_CLKPRESCL_MIN : data;
+ data = data > KWSPI_CLKPRESCL_MASK ? KWSPI_CLKPRESCL_MASK : data;
/* program spi clock prescaller using max_hz */
writel(KWSPI_ADRLEN_3BYTE | data, &spireg->cfg);
--
1.7.1
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