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authorValentin Longchamp <valentin.longchamp@keymile.com>2012-08-15 05:31:49 +0000
committerPrafulla Wadaskar <prafulla@marvell.com>2012-09-03 17:28:51 +0530
commit8203b201eaa1b33758956294b3ec70b326f8ba5c (patch)
tree28a16a951302bfb2adea574bb3d6208899c55cdd
parentf46b4a1aadb4ab834bcf333a9dd4c7804296e185 (diff)
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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>
-rw-r--r--arch/arm/include/asm/arch-kirkwood/spi.h1
-rw-r--r--drivers/spi/kirkwood_spi.c5
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 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 @@ struct kwspi_registers {
#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 */
diff --git a/drivers/spi/kirkwood_spi.c b/drivers/spi/kirkwood_spi.c
index f4523a3..a7cda75 100644
--- a/drivers/spi/kirkwood_spi.c
+++ b/drivers/spi/kirkwood_spi.c
@@ -56,8 +56,9 @@ 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);