[U-Boot] [PATCH] Add I2C speed and divider formula for ColdFire

[U-Boot] [PATCH] Add I2C speed and divider formula for ColdFire

[Tsi-Chung Liew]

From: TsiChung Liew <Tsi-Chung.Liew@freescale.com>

Implement formula to obtain I2C speed and internal bus
divider. This will provide accurate divider than fix table
divider value.

Signed-off-by: TsiChung Liew <Tsi-Chung.Liew@freescale.com>
---
 drivers/i2c/fsl_i2c.c |   76 +++++++++++++++++++++++++++++++++----------------
 1 files changed, 51 insertions(+), 25 deletions(-)

diff --git a/drivers/i2c/fsl_i2c.c b/drivers/i2c/fsl_i2c.c
index 6ab7d3d..7f6d864 100644
--- a/drivers/i2c/fsl_i2c.c
+++ b/drivers/i2c/fsl_i2c.c
@@ -84,14 +84,12 @@ static const struct fsl_i2c *i2c_dev[2] = {
  * A different table is defined and are based on MCF5xxx user manual.
  *
  */
+#ifdef __PPC__
 static const struct {
 	unsigned short divider;
-#ifdef __PPC__
 	u8 dfsr;
-#endif
 	u8 fdr;
 } fsl_i2c_speed_map[] = {
-#ifdef __PPC__
 	{160, 1, 32}, {192, 1, 33}, {224, 1, 34}, {256, 1, 35},
 	{288, 1, 0}, {320, 1, 1}, {352, 6, 1}, {384, 1, 2}, {416, 6, 2},
 	{448, 1, 38}, {480, 1, 3}, {512, 1, 39}, {544, 11, 3}, {576, 1, 4},
@@ -108,26 +106,22 @@ static const struct {
 	{20480, 1, 25}, {24576, 1, 26}, {28672, 1, 62}, {30720, 1, 27},
 	{32768, 1, 63}, {36864, 1, 28}, {40960, 1, 29}, {49152, 1, 30},
 	{61440, 1, 31}, {-1, 1, 31}
+};
 #elif defined(__M68K__)
-	{20, 32}, {22, 33}, {24, 34}, {26, 35},
-	{28, 0}, {28, 36}, {30, 1}, {32, 37},
-	{34, 2}, {36, 38}, {40, 3}, {40, 39},
-	{44, 4}, {48, 5}, {48, 40}, {56, 6},
-	{56, 41}, {64, 42}, {68, 7}, {72, 43},
-	{80, 8}, {80, 44}, {88, 9}, {96, 41},
-	{104, 10}, {112, 42}, {128, 11}, {128, 43},
-	{144, 12}, {160, 13}, {160, 48}, {192, 14},
-	{192, 49}, {224, 50}, {240, 15}, {256, 51},
-	{288, 16}, {320, 17}, {320, 52}, {384, 18},
-	{384, 53}, {448, 54}, {480, 19}, {512, 55},
-	{576, 20}, {640, 21}, {640, 56}, {768, 22},
-	{768, 57}, {960, 23}, {896, 58}, {1024, 59},
-	{1152, 24}, {1280, 25}, {1280, 60}, {1536, 26},
-	{1536, 61}, {1792, 62}, {1920, 27}, {2048, 63},
-	{2304, 28}, {2560, 29}, {3072, 30}, {3840, 31},
-	{-1, 31}
-#endif
+struct coldfire_i2c_tap {
+	int scl2tap;
+	int tap2tap;
+} scltap[] = {
+	{4, 1},
+	{4, 2},
+	{6, 4},
+	{6, 8},
+	{14, 16},
+	{30, 32},
+	{62, 64},
+	{126, 128}
 };
+#endif
 
 /**
  * Set the I2C bus speed for a given I2C device
@@ -143,6 +137,7 @@ static const struct {
 static unsigned int set_i2c_bus_speed(const struct fsl_i2c *dev,
 	unsigned int i2c_clk, unsigned int speed)
 {
+#ifdef __PPC__
 	unsigned short divider = min(i2c_clk / speed, (unsigned short) -1);
 	unsigned int i;
 
@@ -156,20 +151,51 @@ static unsigned int set_i2c_bus_speed(const struct fsl_i2c *dev,
 	for (i = 0; i < ARRAY_SIZE(fsl_i2c_speed_map); i++)
 		if (fsl_i2c_speed_map[i].divider >= divider) {
 			u8 fdr;
-#ifdef __PPC__
 			u8 dfsr;
 			dfsr = fsl_i2c_speed_map[i].dfsr;
-#endif
 			fdr = fsl_i2c_speed_map[i].fdr;
 			speed = i2c_clk / fsl_i2c_speed_map[i].divider;
 			writeb(fdr, &dev->fdr);		/* set bus speed */
-#ifdef __PPC__
 			writeb(dfsr, &dev->dfsrr);	/* set default filter */
-#endif
 			break;
 		}
 
 	return speed;
+#elif defined(__M68K__)
+	int fdr = -1;
+	ulong best_speed = 0;
+	ulong divider;
+	ulong ipb, scl;
+	ulong bestmatch = 0xffffffffUL;
+	int best_i = 0, best_j = 0, i, j;
+	int SCL_Tap[] = { 9, 10, 12, 15, 5, 6, 7, 8 };
+
+	ipb = gd->bus_clk;
+	for (i = 7; i >= 0; i--) {
+		for (j = 7; j >= 0; j--) {
+			scl = 2 * (scltap[j].scl2tap +
+				   (SCL_Tap[i] - 1) * scltap[j].tap2tap + 2);
+			if (ipb <= speed * scl) {
+				if ((speed * scl - ipb) < bestmatch) {
+					bestmatch = speed * scl - ipb;
+					best_i = i;
+					best_j = j;
+					best_speed = ipb / scl;
+				}
+			}
+		}
+	}
+
+	divider = (best_i & 3) | ((best_i & 4) << 3) | (best_j << 2);
+	if (gd->flags & GD_FLG_RELOC)
+		fdr = divider;
+	else
+		printf("%ld kHz, ", best_speed / 1000);
+
+	speed = best_speed;
+
+	return speed;
+#endif
 }
 
 void
-- 
1.5.6.4

[U-Boot] [PATCH] Add I2C speed and divider formula for ColdFire

[Timur Tabi]

On Thu, Apr 9, 2009 at 11:18 AM, Tsi-Chung Liew
<Tsi-Chung.Liew@freescale.com> wrote:
> From: TsiChung Liew <Tsi-Chung.Liew@freescale.com>
>
> Implement formula to obtain I2C speed and internal bus
> divider. This will provide accurate divider than fix table
> divider value.

Can you prove this statement?  I don't think accuracy is that
important.  The advantage of a table is that it's easier to debug and
the code is simpler.

I'm inclined to NACK this patch.

-- 
Timur Tabi
Linux kernel developer at Freescale

[U-Boot] [PATCH] Add I2C speed and divider formula for ColdFire

[Richard Retanubun]

Hi TC,

Sorry for the delay, but I was the original complainer about this issue and finally got a chance to try it out.

Timur Tabi wrote:
> On Thu, Apr 9, 2009 at 11:18 AM, Tsi-Chung Liew
> <Tsi-Chung.Liew@freescale.com> wrote:
>> From: TsiChung Liew <Tsi-Chung.Liew@freescale.com>
>>
>> Implement formula to obtain I2C speed and internal bus
>> divider. This will provide accurate divider than fix table
>> divider value.
> 
> Can you prove this statement?

And the code and boot message thinks it is 390 KHz

U-Boot 2009.03dvl-00089-g61e51f7 (Apr 15 2009 - 11:20:06)

CPU:   Freescale ColdFire MCF5270 rev. 1, at 150 MHz
I2C:   390 kHz, ready
[snip]
=> i2c speed
Current bus speed=390625

My probed i2c clock changes from 390KHz (with my patch) to 2MHz with your patch (the ideal being 400KHz)

so NAK from me as well.

- Richard