summaryrefslogtreecommitdiff
path: root/drivers/i2c/mxs_i2c.c
diff options
context:
space:
mode:
Diffstat (limited to 'drivers/i2c/mxs_i2c.c')
-rw-r--r--drivers/i2c/mxs_i2c.c82
1 files changed, 57 insertions, 25 deletions
diff --git a/drivers/i2c/mxs_i2c.c b/drivers/i2c/mxs_i2c.c
index 2a193c2..b907f7b 100644
--- a/drivers/i2c/mxs_i2c.c
+++ b/drivers/i2c/mxs_i2c.c
@@ -28,6 +28,7 @@
#include <common.h>
#include <malloc.h>
+#include <i2c.h>
#include <asm/errno.h>
#include <asm/io.h>
#include <asm/arch/clock.h>
@@ -40,6 +41,7 @@ void mxs_i2c_reset(void)
{
struct mxs_i2c_regs *i2c_regs = (struct mxs_i2c_regs *)MXS_I2C0_BASE;
int ret;
+ int speed = i2c_get_bus_speed();
ret = mxs_reset_block(&i2c_regs->hw_i2c_ctrl0_reg);
if (ret) {
@@ -53,6 +55,8 @@ void mxs_i2c_reset(void)
&i2c_regs->hw_i2c_ctrl1_clr);
writel(I2C_QUEUECTRL_PIO_QUEUE_MODE, &i2c_regs->hw_i2c_queuectrl_set);
+
+ i2c_set_bus_speed(speed);
}
void mxs_i2c_setup_read(uint8_t chip, int len)
@@ -210,37 +214,65 @@ int i2c_probe(uchar chip)
return ret;
}
-void i2c_init(int speed, int slaveadd)
+int i2c_set_bus_speed(unsigned int speed)
{
struct mxs_i2c_regs *i2c_regs = (struct mxs_i2c_regs *)MXS_I2C0_BASE;
+ /*
+ * The timing derivation algorithm. There is no documentation for this
+ * algorithm available, it was derived by using the scope and fiddling
+ * with constants until the result observed on the scope was good enough
+ * for 20kHz, 50kHz, 100kHz, 200kHz, 300kHz and 400kHz. It should be
+ * possible to assume the algorithm works for other frequencies as well.
+ *
+ * Note it was necessary to cap the frequency on both ends as it's not
+ * possible to configure completely arbitrary frequency for the I2C bus
+ * clock.
+ */
+ uint32_t clk = mxc_get_clock(MXC_XTAL_CLK);
+ uint32_t base = ((clk / speed) - 38) / 2;
+ uint16_t high_count = base + 3;
+ uint16_t low_count = base - 3;
+ uint16_t rcv_count = (high_count * 3) / 4;
+ uint16_t xmit_count = low_count / 4;
+
+ if (speed > 540000) {
+ printf("MXS I2C: Speed too high (%d Hz)\n", speed);
+ return -EINVAL;
+ }
- mxs_i2c_reset();
-
- switch (speed) {
- case 100000:
- writel((0x0078 << I2C_TIMING0_HIGH_COUNT_OFFSET) |
- (0x0030 << I2C_TIMING0_RCV_COUNT_OFFSET),
- &i2c_regs->hw_i2c_timing0);
- writel((0x0080 << I2C_TIMING1_LOW_COUNT_OFFSET) |
- (0x0030 << I2C_TIMING1_XMIT_COUNT_OFFSET),
- &i2c_regs->hw_i2c_timing1);
- break;
- case 400000:
- writel((0x000f << I2C_TIMING0_HIGH_COUNT_OFFSET) |
- (0x0007 << I2C_TIMING0_RCV_COUNT_OFFSET),
- &i2c_regs->hw_i2c_timing0);
- writel((0x001f << I2C_TIMING1_LOW_COUNT_OFFSET) |
- (0x000f << I2C_TIMING1_XMIT_COUNT_OFFSET),
- &i2c_regs->hw_i2c_timing1);
- break;
- default:
- printf("MXS I2C: Invalid speed selected (%d Hz)\n", speed);
- return;
+ if (speed < 12000) {
+ printf("MXS I2C: Speed too low (%d Hz)\n", speed);
+ return -EINVAL;
}
- writel((0x0015 << I2C_TIMING2_BUS_FREE_OFFSET) |
- (0x000d << I2C_TIMING2_LEADIN_COUNT_OFFSET),
+ writel((high_count << 16) | rcv_count, &i2c_regs->hw_i2c_timing0);
+ writel((low_count << 16) | xmit_count, &i2c_regs->hw_i2c_timing1);
+
+ writel((0x0030 << I2C_TIMING2_BUS_FREE_OFFSET) |
+ (0x0030 << I2C_TIMING2_LEADIN_COUNT_OFFSET),
&i2c_regs->hw_i2c_timing2);
+ return 0;
+}
+
+unsigned int i2c_get_bus_speed(void)
+{
+ struct mxs_i2c_regs *i2c_regs = (struct mxs_i2c_regs *)MXS_I2C0_BASE;
+ uint32_t clk = mxc_get_clock(MXC_XTAL_CLK);
+ uint32_t timing0;
+
+ timing0 = readl(&i2c_regs->hw_i2c_timing0);
+ /*
+ * This is a reverse version of the algorithm presented in
+ * i2c_set_bus_speed(). Please refer there for details.
+ */
+ return clk / ((((timing0 >> 16) - 3) * 2) + 38);
+}
+
+void i2c_init(int speed, int slaveadd)
+{
+ mxs_i2c_reset();
+ i2c_set_bus_speed(speed);
+
return;
}