[U-Boot] [PATCH V2 09/11] SPI: mxc_spi: add SPI clock calculation and setup to the driver

Stefano Babic
2011-01-20T08:46:32Z

From: Anatolij Gustschin <agust@denx.de>

The MXC SPI driver didn't calculate the SPI clock up to
now and just used highest possible divider 512 for DATA
RATE in the control register. This results in very low
transfer rates.

The patch adds code to calculate and setup the SPI clock
frequency for transfers.

Signed-off-by: Anatolij Gustschin <agust@denx.de>
Signed-off-by: Stefano Babic <sbabic@denx.de>
---
Changes:

Sergei Shtylyov:
- fix commit message

drivers/spi/mxc_spi.c | 23 ++++++++++++++++++++++-
1 files changed, 22 insertions(+), 1 deletions(-)

diff --git a/drivers/spi/mxc_spi.c b/drivers/spi/mxc_spi.c
index 3e99afd..ee7675b 100644
--- a/drivers/spi/mxc_spi.c
+++ b/drivers/spi/mxc_spi.c
@@ -199,15 +199,36 @@ void spi_cs_deactivate(struct spi_slave *slave)
!(mxcs->ss_pol));
}

+u32 get_cspi_div(u32 div)
+{
+ int i;
+
+ for (i = 0; i < 8; i++) {
+ if (div <= (4 << i))
+ return i;
+ }
+ return i;
+}
+
#if defined(CONFIG_MX31) || defined(CONFIG_MX35)
static s32 spi_cfg_mxc(struct mxc_spi_slave *mxcs, unsigned int cs,
unsigned int max_hz, unsigned int mode)
{
unsigned int ctrl_reg;
+ u32 clk_src;
+ u32 div;
+
+ clk_src = mxc_get_clock(MXC_CSPI_CLK);
+
+ div = clk_src / max_hz;
+ div = get_cspi_div(div);
+
+ debug("clk %d Hz, div %d, real clk %d Hz\n",
+ max_hz, div, clk_src / (4 << div));

ctrl_reg = MXC_CSPICTRL_CHIPSELECT(cs) |
MXC_CSPICTRL_BITCOUNT(MXC_CSPICTRL_MAXBITS) |
- MXC_CSPICTRL_DATARATE(7) | /* FIXME: calculate data rate */
+ MXC_CSPICTRL_DATARATE(div) |
MXC_CSPICTRL_EN |
#ifdef CONFIG_MX35
MXC_CSPICTRL_SSCTL |
--
1.7.1