[PATCH 09/11] i2c: imx-lpi2c: fix i2c timing issue

[Clark Wang]

The clkhi and clklo ratio was not very precise before that can make the
time of START/STOP/HIGH LEVEL out of specification.

Therefore, the calculation of these times has been modified in this patch.
At the same time, the mode rate definition of i2c is corrected.

Reviewed-by: Fugang Duan <fugang.d...@nxp.com>
Signed-off-by: Clark Wang <xiaoning.w...@nxp.com>
---
 drivers/i2c/busses/i2c-imx-lpi2c.c | 27 ++++++++++++++-------------
 1 file changed, 14 insertions(+), 13 deletions(-)

diff --git a/drivers/i2c/busses/i2c-imx-lpi2c.c 
b/drivers/i2c/busses/i2c-imx-lpi2c.c
index 7216a393095d..5dbe85126f24 100644
--- a/drivers/i2c/busses/i2c-imx-lpi2c.c
+++ b/drivers/i2c/busses/i2c-imx-lpi2c.c
@@ -73,17 +73,17 @@
 #define MCFGR1_IGNACK  BIT(9)
 #define MRDR_RXEMPTY   BIT(14)
 
-#define I2C_CLK_RATIO  2
+#define I2C_CLK_RATIO  24 / 59
 #define CHUNK_DATA     256
 
 #define I2C_PM_TIMEOUT         1000 /* ms */
 
 enum lpi2c_imx_mode {
-       STANDARD,       /* 100+Kbps */
-       FAST,           /* 400+Kbps */
-       FAST_PLUS,      /* 1.0+Mbps */
-       HS,             /* 3.4+Mbps */
-       ULTRA_FAST,     /* 5.0+Mbps */
+       STANDARD,       /* <=100Kbps */
+       FAST,           /* <=400Kbps */
+       FAST_PLUS,      /* <=1.0Mbps */
+       HS,             /* <=3.4Mbps */
+       ULTRA_FAST,     /* <=5.0Mbps */
 };
 
 enum lpi2c_imx_pincfg {
@@ -156,13 +156,13 @@ static void lpi2c_imx_set_mode(struct lpi2c_imx_struct 
*lpi2c_imx)
        unsigned int bitrate = lpi2c_imx->bitrate;
        enum lpi2c_imx_mode mode;
 
-       if (bitrate < I2C_MAX_FAST_MODE_FREQ)
+       if (bitrate <= I2C_MAX_STANDARD_MODE_FREQ)
                mode = STANDARD;
-       else if (bitrate < I2C_MAX_FAST_MODE_PLUS_FREQ)
+       else if (bitrate <= I2C_MAX_FAST_MODE_FREQ)
                mode = FAST;
-       else if (bitrate < I2C_MAX_HIGH_SPEED_MODE_FREQ)
+       else if (bitrate <= I2C_MAX_FAST_MODE_PLUS_FREQ)
                mode = FAST_PLUS;
-       else if (bitrate < I2C_MAX_ULTRA_FAST_MODE_FREQ)
+       else if (bitrate <= I2C_MAX_HIGH_SPEED_MODE_FREQ)
                mode = HS;
        else
                mode = ULTRA_FAST;
@@ -209,7 +209,8 @@ static void lpi2c_imx_stop(struct lpi2c_imx_struct 
*lpi2c_imx)
        } while (1);
 }
 
-/* CLKLO = I2C_CLK_RATIO * CLKHI, SETHOLD = CLKHI, DATAVD = CLKHI/2 */
+/* CLKLO = (1 - I2C_CLK_RATIO) * clk_cycle, SETHOLD = CLKHI, DATAVD = CLKHI/2
+   CLKHI = I2C_CLK_RATIO * clk_cycle */
 static int lpi2c_imx_config(struct lpi2c_imx_struct *lpi2c_imx)
 {
        u8 prescale, filt, sethold, clkhi, clklo, datavd;
@@ -232,8 +233,8 @@ static int lpi2c_imx_config(struct lpi2c_imx_struct 
*lpi2c_imx)
 
        for (prescale = 0; prescale <= 7; prescale++) {
                clk_cycle = clk_rate / ((1 << prescale) * lpi2c_imx->bitrate)
-                           - 3 - (filt >> 1);
-               clkhi = (clk_cycle + I2C_CLK_RATIO) / (I2C_CLK_RATIO + 1);
+                           - (2 + filt) / (1 << prescale);
+               clkhi = clk_cycle * I2C_CLK_RATIO;
                clklo = clk_cycle - clkhi;
                if (clklo < 64)
                        break;
-- 
2.25.1