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.longchamp@keymile.com cc: Holger Brunck holger.brunck@keymile.com cc: Prafulla Wadaskar prafulla@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);