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kw_spi: fix clock prescaler computation

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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>
This commit is contained in:
Valentin Longchamp 2012-08-15 05:31:49 +00:00 committed by Prafulla Wadaskar
parent f46b4a1aad
commit 8203b201ea
2 changed files with 4 additions and 2 deletions
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1
arch/arm/include/asm/arch-kirkwood/spi.h
View File

@ -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 */

5
drivers/spi/kirkwood_spi.c
View File

@ -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);