[U-Boot] [PATCH RFC 0/4] ARMV7: OMAP: I2C driver: Restructure code to eliminate udelay calls and improve performance

[U-Boot] [PATCH RFC 0/4] ARMV7: OMAP: I2C driver: Restructure code to eliminate udelay calls and improve performance

[Steve Sakoman]

I've been preparing a patch series for Beagle and Overo that detects expansion
board configuration information by reading a 128 byte I2C EEPROM on each
expansion board.

Using the OMAP I2C driver in its current form takes about 5-6 seconds to read
this small number of bytes!  Executing the i2c probe command takes close
to 10 seconds.

Examining the code I see that there are a large number of fairly long udelay calls
throughout the driver (10 - 50 milliseconds). I looked through the linux driver
and did not see equivalent delays in that code.  In fact the longest delay in the
linux code was one millisecond.

In looking at the TRM I2C section for OMAP3 and OMAP4 I don't see any requirement
for delays in the programming model description.

This patch restructures the i2c driver to eliminate most of the udelay calls
by monitoring state changes in the status register.

The EEPROM reads and the i2c probe execution are now instantaneous.

This patch series was tested on OMAP3 (Overo) and OMAP4 (Panda).  I do not
have access to OMAP2 hardware for testing.

Steve Sakoman (4):
  ARMV7: OMAP: I2C driver: Use same timeout value as linux kernel
    driver
  ARMV7: OMAP: I2C driver: Restructure i2c_read_byte function
  ARMV7: OMAP: I2C driver: Restructure i2c_write_byte function
  ARMV7: OMAP: I2C driver: Restructure i2c_probe function

 drivers/i2c/omap24xx_i2c.c |  204 ++++++++++++++++++++++++-------------------
 1 files changed, 114 insertions(+), 90 deletions(-)

[U-Boot] [PATCH RFC 1/4] ARMV7: OMAP: I2C driver: Use same timeout value as linux kernel driver

[Steve Sakoman]

This patch matches the poll interval (1 millisecond) and timeout (1 second)
used in the linux driver. It also adds a return value of 0 in the event of
a timeout error and cleans up some formatting errors in that section of the
code.

Signed-off-by: Steve Sakoman <steve.sakoman@linaro.org>
---
 drivers/i2c/omap24xx_i2c.c |   14 ++++++++------
 1 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/drivers/i2c/omap24xx_i2c.c b/drivers/i2c/omap24xx_i2c.c
index 3febd1f..b69d051 100644
--- a/drivers/i2c/omap24xx_i2c.c
+++ b/drivers/i2c/omap24xx_i2c.c
@@ -27,7 +27,7 @@
 
 #include "omap24xx_i2c.h"
 
-#define I2C_TIMEOUT	10
+#define I2C_TIMEOUT	1000
 
 static void wait_for_bb (void);
 static u16 wait_for_pin (void);
@@ -392,13 +392,13 @@ int i2c_write (uchar chip, uint addr, int alen, uchar * buffer, int len)
 
 static void wait_for_bb (void)
 {
-	int timeout = 10;
+	int timeout = I2C_TIMEOUT;
 	u16 stat;
 
 	writew(0xFFFF, &i2c_base->stat);	 /* clear current interruts...*/
 	while ((stat = readw (&i2c_base->stat) & I2C_STAT_BB) && timeout--) {
 		writew (stat, &i2c_base->stat);
-		udelay (50000);
+		udelay(1000);
 	}
 
 	if (timeout <= 0) {
@@ -411,7 +411,7 @@ static void wait_for_bb (void)
 static u16 wait_for_pin (void)
 {
 	u16 status;
-	int timeout = 10;
+	int timeout = I2C_TIMEOUT;
 
 	do {
 		udelay (1000);
@@ -424,8 +424,10 @@ static u16 wait_for_pin (void)
 	if (timeout <= 0) {
 		printf ("timed out in wait_for_pin: I2C_STAT=%x\n",
 			readw (&i2c_base->stat));
-			writew(0xFFFF, &i2c_base->stat);
-}
+		writew(0xFFFF, &i2c_base->stat);
+		status = 0;
+	}
+
 	return status;
 }
 
-- 
1.7.0.4

[U-Boot] [PATCH RFC 1/4] ARMV7: OMAP: I2C driver: Use same timeout value as linux kernel driver

[Heiko Schocher]

Hello Steve,

Steve Sakoman wrote:
> This patch matches the poll interval (1 millisecond) and timeout (1 second)
> used in the linux driver. It also adds a return value of 0 in the event of
> a timeout error and cleans up some formatting errors in that section of the
> code.
> 
> Signed-off-by: Steve Sakoman <steve.sakoman@linaro.org>
> ---
>  drivers/i2c/omap24xx_i2c.c |   14 ++++++++------
>  1 files changed, 8 insertions(+), 6 deletions(-)

Applied to u-boot-i2c master

Thanks!

bye,
Heiko
-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany

[U-Boot] [PATCH RFC 2/4] ARMV7: OMAP: I2C driver: Restructure i2c_read_byte function

[Steve Sakoman]

This patch removes the "magic number" delays and instead
monitors state changes in the status register bits.

Signed-off-by: Steve Sakoman <steve.sakomanlinaro.org>
---
 drivers/i2c/omap24xx_i2c.c |   76 +++++++++++++++++++++----------------------
 1 files changed, 37 insertions(+), 39 deletions(-)

diff --git a/drivers/i2c/omap24xx_i2c.c b/drivers/i2c/omap24xx_i2c.c
index b69d051..d176b5d 100644
--- a/drivers/i2c/omap24xx_i2c.c
+++ b/drivers/i2c/omap24xx_i2c.c
@@ -159,58 +159,56 @@ static int i2c_read_byte (u8 devaddr, u8 regoffset, u8 * value)
 	/* no stop bit needed here */
 	writew (I2C_CON_EN | I2C_CON_MST | I2C_CON_STT | I2C_CON_TRX, &i2c_base->con);
 
-	status = wait_for_pin ();
-
-	if (status & I2C_STAT_XRDY) {
-		/* Important: have to use byte access */
-		writeb (regoffset, &i2c_base->data);
-		udelay (20000);
-		if (readw (&i2c_base->stat) & I2C_STAT_NACK) {
+	/* send register offset */
+	while (1) {
+		status = wait_for_pin();
+		if (status == 0 || status & I2C_STAT_NACK) {
 			i2c_error = 1;
+			goto read_exit;
+		}
+		if (status & I2C_STAT_XRDY) {
+			/* Important: have to use byte access */
+			writeb(regoffset, &i2c_base->data);
+			writew(I2C_STAT_XRDY, &i2c_base->stat);
+		}
+		if (status & I2C_STAT_ARDY) {
+			writew(I2C_STAT_ARDY, &i2c_base->stat);
+			break;
 		}
-	} else {
-		i2c_error = 1;
 	}
 
-	if (!i2c_error) {
-		writew (I2C_CON_EN, &i2c_base->con);
-		while (readw(&i2c_base->stat) &
-			(I2C_STAT_XRDY | I2C_STAT_ARDY)) {
-			udelay (10000);
-			/* Have to clear pending interrupt to clear I2C_STAT */
-			writew (0xFFFF, &i2c_base->stat);
+	/* set slave address */
+	writew(devaddr, &i2c_base->sa);
+	/* read one byte from slave */
+	writew(1, &i2c_base->cnt);
+	/* need stop bit here */
+	writew(I2C_CON_EN | I2C_CON_MST |
+		I2C_CON_STT | I2C_CON_STP,
+		&i2c_base->con);
+
+	/* receive data */
+	while (1) {
+		status = wait_for_pin();
+		if (status == 0 || status & I2C_STAT_NACK) {
+			i2c_error = 1;
+			goto read_exit;
 		}
-
-		/* set slave address */
-		writew (devaddr, &i2c_base->sa);
-		/* read one byte from slave */
-		writew (1, &i2c_base->cnt);
-		/* need stop bit here */
-		writew (I2C_CON_EN | I2C_CON_MST | I2C_CON_STT | I2C_CON_STP,
-			&i2c_base->con);
-
-		status = wait_for_pin ();
 		if (status & I2C_STAT_RRDY) {
 #if defined(CONFIG_OMAP243X) || defined(CONFIG_OMAP34XX) || \
     defined(CONFIG_OMAP44XX)
-			*value = readb (&i2c_base->data);
+			*value = readb(&i2c_base->data);
 #else
-			*value = readw (&i2c_base->data);
+			*value = readw(&i2c_base->data);
 #endif
-			udelay (20000);
-		} else {
-			i2c_error = 1;
+			writew(I2C_STAT_RRDY, &i2c_base->stat);
 		}
-
-		if (!i2c_error) {
-			writew (I2C_CON_EN, &i2c_base->con);
-			while (readw (&i2c_base->stat) &
-				(I2C_STAT_RRDY | I2C_STAT_ARDY)) {
-				udelay (10000);
-				writew (0xFFFF, &i2c_base->stat);
-			}
+		if (status & I2C_STAT_ARDY) {
+			writew(I2C_STAT_ARDY, &i2c_base->stat);
+			break;
 		}
 	}
+
+read_exit:
 	flush_fifo();
 	writew (0xFFFF, &i2c_base->stat);
 	writew (0, &i2c_base->cnt);
-- 
1.7.0.4

[U-Boot] [PATCH RFC 2/4] ARMV7: OMAP: I2C driver: Restructure i2c_read_byte function

[Heiko Schocher]

Hello Steve,

Steve Sakoman wrote:
> This patch removes the "magic number" delays and instead
> monitors state changes in the status register bits.
> 
> Signed-off-by: Steve Sakoman <steve.sakomanlinaro.org>
> ---
>  drivers/i2c/omap24xx_i2c.c |   76 +++++++++++++++++++++----------------------
>  1 files changed, 37 insertions(+), 39 deletions(-)

Applied to u-boot-i2c master

Thanks!

bye,
Heiko
-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany

[U-Boot] [PATCH RFC 3/4] ARMV7: OMAP: I2C driver: Restructure i2c_write_byte function

[Steve Sakoman]

This patch removes the "magic number" delays and instead
monitors state changes in the status register bits.

Signed-off-by: Steve Sakoman <steve.sakoman@linaro.org>
---
 drivers/i2c/omap24xx_i2c.c |   76 +++++++++++++++++++++++--------------------
 1 files changed, 41 insertions(+), 35 deletions(-)

diff --git a/drivers/i2c/omap24xx_i2c.c b/drivers/i2c/omap24xx_i2c.c
index d176b5d..828264e 100644
--- a/drivers/i2c/omap24xx_i2c.c
+++ b/drivers/i2c/omap24xx_i2c.c
@@ -231,49 +231,55 @@ static int i2c_write_byte (u8 devaddr, u8 regoffset, u8 value)
 	writew (I2C_CON_EN | I2C_CON_MST | I2C_CON_STT | I2C_CON_TRX |
 		I2C_CON_STP, &i2c_base->con);
 
-	/* wait until state change */
-	status = wait_for_pin ();
-
-	if (status & I2C_STAT_XRDY) {
-#if defined(CONFIG_OMAP243X) || defined(CONFIG_OMAP34XX) || \
-    defined(CONFIG_OMAP44XX)
-		/* send out 1 byte */
-		writeb (regoffset, &i2c_base->data);
-		writew (I2C_STAT_XRDY, &i2c_base->stat);
-
-		status = wait_for_pin ();
-		if ((status & I2C_STAT_XRDY)) {
-			/* send out next 1 byte */
-			writeb (value, &i2c_base->data);
-			writew (I2C_STAT_XRDY, &i2c_base->stat);
-		} else {
+	while (1) {
+		status = wait_for_pin();
+		if (status == 0 || status & I2C_STAT_NACK) {
 			i2c_error = 1;
+			goto write_exit;
 		}
+		if (status & I2C_STAT_XRDY) {
+#if defined(CONFIG_OMAP243X) || defined(CONFIG_OMAP34XX) || \
+    defined(CONFIG_OMAP44XX)
+			/* send register offset */
+			writeb(regoffset, &i2c_base->data);
+			writew(I2C_STAT_XRDY, &i2c_base->stat);
+
+			while (1) {
+				status = wait_for_pin();
+				if (status == 0 || status & I2C_STAT_NACK) {
+					i2c_error = 1;
+					goto write_exit;
+				}
+				if (status & I2C_STAT_XRDY) {
+					/* send data */
+					writeb(value, &i2c_base->data);
+					writew(I2C_STAT_XRDY, &i2c_base->stat);
+				}
+				if (status & I2C_STAT_ARDY) {
+					writew(I2C_STAT_ARDY, &i2c_base->stat);
+					break;
+				}
+			}
+			break;
 #else
-		/* send out two bytes */
-		writew ((value << 8) + regoffset, &i2c_base->data);
+			/* send out two bytes */
+			writew((value << 8) + regoffset, &i2c_base->data);
+			writew(I2C_STAT_XRDY, &i2c_base->stat);
 #endif
-		/* must have enough delay to allow BB bit to go low */
-		udelay (50000);
-		if (readw (&i2c_base->stat) & I2C_STAT_NACK) {
-			i2c_error = 1;
 		}
-	} else {
-		i2c_error = 1;
+		if (status & I2C_STAT_ARDY) {
+			writew(I2C_STAT_ARDY, &i2c_base->stat);
+			break;
+		}
 	}
 
-	if (!i2c_error) {
-		int eout = 200;
+	wait_for_bb();
 
-		writew (I2C_CON_EN, &i2c_base->con);
-		while ((stat = readw (&i2c_base->stat)) || (readw (&i2c_base->con) & I2C_CON_MST)) {
-			udelay (1000);
-			/* have to read to clear intrrupt */
-			writew (0xFFFF, &i2c_base->stat);
-			if(--eout == 0) /* better leave with error than hang */
-				break;
-		}
-	}
+	status = readw(&i2c_base->stat);
+	if (status & I2C_STAT_NACK)
+		i2c_error = 1;
+
+write_exit:
 	flush_fifo();
 	writew (0xFFFF, &i2c_base->stat);
 	writew (0, &i2c_base->cnt);
-- 
1.7.0.4

[U-Boot] [PATCH RFC 3/4] ARMV7: OMAP: I2C driver: Restructure i2c_write_byte function

[Heiko Schocher]

Hello Steve,

Steve Sakoman wrote:
> This patch removes the "magic number" delays and instead
> monitors state changes in the status register bits.
> 
> Signed-off-by: Steve Sakoman <steve.sakoman@linaro.org>
> ---
>  drivers/i2c/omap24xx_i2c.c |   76 +++++++++++++++++++++++--------------------
>  1 files changed, 41 insertions(+), 35 deletions(-)

Applied to u-boot-i2c master

Thanks!

bye,
Heiko
-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany

[U-Boot] [PATCH RFC 3/4] ARMV7: OMAP: I2C driver: Restructure i2c_write_byte function

[Heiko Schocher]

Hello Steve,

Steve Sakoman wrote:
> This patch removes the "magic number" delays and instead
> monitors state changes in the status register bits.
> 
> Signed-off-by: Steve Sakoman <steve.sakoman@linaro.org>
> ---
>  drivers/i2c/omap24xx_i2c.c |   76 +++++++++++++++++++++++--------------------
>  1 files changed, 41 insertions(+), 35 deletions(-)

After trying this for the omap3_beagle board, I get an
compiler warning:

[hs at pollux u-boot]$ ./MAKEALL omap3_beagle
Configuring for omap3_beagle board...
omap24xx_i2c.c: In function 'i2c_write_byte':
omap24xx_i2c.c:221: warning: unused variable 'stat'
   text    data     bss     dec     hex filename
 218103   11412  202384  431899   6971b ./u-boot

--------------------- SUMMARY ----------------------------
Boards compiled: 1
Boards with warnings or errors: 1 ( omap3_beagle )
----------------------------------------------------------
[hs at pollux u-boot]$

following patch fixes it.

BTW:
Just for the record, your patchset works fine and faster
on the beagle board, for example:

                 before your  after your
                 patchset     patchset
i2c probe        9s           0,4s
i2c md 48 0 100  17s          1s

would you post a v2 of this patch, and I add my
"Tested-by" to it, or is it OK, if I add my fix patch
to u-boot-i2c master?

[U-Boot] [PATCH RFC 3/4] ARMV7: OMAP: I2C driver: Restructure i2c_write_byte function

[Steve Sakoman]

On Wed, 2010-10-20 at 08:08 +0200, Heiko Schocher wrote:
> Hello Steve,
> 
> Steve Sakoman wrote:
> > This patch removes the "magic number" delays and instead
> > monitors state changes in the status register bits.
> > 
> > Signed-off-by: Steve Sakoman <steve.sakoman@linaro.org>
> > ---
> >  drivers/i2c/omap24xx_i2c.c |   76 +++++++++++++++++++++++--------------------
> >  1 files changed, 41 insertions(+), 35 deletions(-)
> 
> After trying this for the omap3_beagle board, I get an
> compiler warning:
> 
> [hs at pollux u-boot]$ ./MAKEALL omap3_beagle
> Configuring for omap3_beagle board...
> omap24xx_i2c.c: In function 'i2c_write_byte':
> omap24xx_i2c.c:221: warning: unused variable 'stat'

Hmm . . . I can swear I fixed that!  Must be getting old :-)

>    text    data     bss     dec     hex filename
>  218103   11412  202384  431899   6971b ./u-boot
> 
> --------------------- SUMMARY ----------------------------
> Boards compiled: 1
> Boards with warnings or errors: 1 ( omap3_beagle )
> ----------------------------------------------------------
> [hs at pollux u-boot]$
> 
> following patch fixes it.
> 
> BTW:
> Just for the record, your patchset works fine and faster
> on the beagle board, for example:
> 
>                  before your  after your
>                  patchset     patchset
> i2c probe        9s           0,4s
> i2c md 48 0 100  17s          1s

I'm glad that you see the same speedups!

What tool do you use to measure the speedups?

> would you post a v2 of this patch, and I add my
> "Tested-by" to it, or is it OK, if I add my fix patch
> to u-boot-i2c master?

I've posted v2 with your "Tested-by" and the warning fix.

If it helps, the patches are in my omap4-next-upstream branch:

http://www.sakoman.com/cgi-bin/gitweb.cgi?p=u-boot.git;a=shortlog;h=refs/heads/omap4-next-upstream

Thanks for testing and for the comments!

Steve

> From 01c6c59014c4174ad4d13944d740d3491d9cf137 Mon Sep 17 00:00:00 2001
> From: Heiko Schocher <hs@denx.de>
> Date: Wed, 20 Oct 2010 07:57:05 +0200
> Subject: [PATCH] ARMV7: OMAP: I2C driver: fix compiler warning
> 
> Signed-off-by: Heiko Schocher <hs@denx.de>
> ---
>  drivers/i2c/omap24xx_i2c.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/i2c/omap24xx_i2c.c b/drivers/i2c/omap24xx_i2c.c
> index eb153fb..a72d1a1 100644
> --- a/drivers/i2c/omap24xx_i2c.c
> +++ b/drivers/i2c/omap24xx_i2c.c
> @@ -218,7 +218,7 @@ read_exit:
>  static int i2c_write_byte (u8 devaddr, u8 regoffset, u8 value)
>  {
>  	int i2c_error = 0;
> -	u16 status, stat;
> +	u16 status;
> 
>  	/* wait until bus not busy */
>  	wait_for_bb ();
> 
> bye,
> Heiko

[U-Boot] [PATCH RFC 3/4] ARMV7: OMAP: I2C driver: Restructure i2c_write_byte function

[Heiko Schocher]

Hello Steve,

Steve Sakoman wrote:
> On Wed, 2010-10-20 at 08:08 +0200, Heiko Schocher wrote:
>> Hello Steve,
>>
>> Steve Sakoman wrote:
>>> This patch removes the "magic number" delays and instead
>>> monitors state changes in the status register bits.
>>>
>>> Signed-off-by: Steve Sakoman <steve.sakoman@linaro.org>
>>> ---
>>>  drivers/i2c/omap24xx_i2c.c |   76 +++++++++++++++++++++++--------------------
>>>  1 files changed, 41 insertions(+), 35 deletions(-)
>> After trying this for the omap3_beagle board, I get an
>> compiler warning:
>>
>> [hs at pollux u-boot]$ ./MAKEALL omap3_beagle
>> Configuring for omap3_beagle board...
>> omap24xx_i2c.c: In function 'i2c_write_byte':
>> omap24xx_i2c.c:221: warning: unused variable 'stat'
> 
> Hmm . . . I can swear I fixed that!  Must be getting old :-)

;-)

>>    text    data     bss     dec     hex filename
>>  218103   11412  202384  431899   6971b ./u-boot
>>
>> --------------------- SUMMARY ----------------------------
>> Boards compiled: 1
>> Boards with warnings or errors: 1 ( omap3_beagle )
>> ----------------------------------------------------------
>> [hs at pollux u-boot]$
>>
>> following patch fixes it.
>>
>> BTW:
>> Just for the record, your patchset works fine and faster
>> on the beagle board, for example:
>>
>>                  before your  after your
>>                  patchset     patchset
>> i2c probe        9s           0,4s
>> i2c md 48 0 100  17s          1s
> 
> I'm glad that you see the same speedups!
> 
> What tool do you use to measure the speedups?

You find it here:
ftp://ftp.denx.de/pub/tools/time_log

You can start this script for example with:

kermit -c 2>&1 | ./time_log "start"

and then measure with for example:

echo start;i2c md 48 0 100;echo stop

and you get the time the command(s) between start
and stop needed ...

>> would you post a v2 of this patch, and I add my
>> "Tested-by" to it, or is it OK, if I add my fix patch
>> to u-boot-i2c master?
> 
> I've posted v2 with your "Tested-by" and the warning fix.

Ok, thanks!

bye,
Heiko
-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany

[U-Boot] [PATCH RFC 4/4] ARMV7: OMAP: I2C driver: Restructure i2c_probe function

[Steve Sakoman]

This patch removes the "magic number" delays and instead
monitors state changes in the status register bits.

Signed-off-by: Steve Sakoman <steve.sakoman@linaro.org>
---
 drivers/i2c/omap24xx_i2c.c |   41 ++++++++++++++++++++++++++++++-----------
 1 files changed, 30 insertions(+), 11 deletions(-)

diff --git a/drivers/i2c/omap24xx_i2c.c b/drivers/i2c/omap24xx_i2c.c
index 828264e..eb153fb 100644
--- a/drivers/i2c/omap24xx_i2c.c
+++ b/drivers/i2c/omap24xx_i2c.c
@@ -310,6 +310,7 @@ static void flush_fifo(void)
 
 int i2c_probe (uchar chip)
 {
+	u16 status;
 	int res = 1; /* default = fail */
 
 	if (chip == readw (&i2c_base->oa)) {
@@ -325,19 +326,37 @@ int i2c_probe (uchar chip)
 	writew (chip, &i2c_base->sa);
 	/* stop bit needed here */
 	writew (I2C_CON_EN | I2C_CON_MST | I2C_CON_STT | I2C_CON_STP, &i2c_base->con);
-	/* enough delay for the NACK bit set */
-	udelay (50000);
 
-	if (!(readw (&i2c_base->stat) & I2C_STAT_NACK)) {
-		res = 0;      /* success case */
-		flush_fifo();
-		writew(0xFFFF, &i2c_base->stat);
-	} else {
-		writew(0xFFFF, &i2c_base->stat);	 /* failue, clear sources*/
-		writew (readw (&i2c_base->con) | I2C_CON_STP, &i2c_base->con); /* finish up xfer */
-		udelay(20000);
-		wait_for_bb ();
+	while (1) {
+		status = wait_for_pin();
+		if (status == 0) {
+			res = 1;
+			goto probe_exit;
+		}
+		if (status & I2C_STAT_NACK) {
+			res = 1;
+			writew(0xff, &i2c_base->stat);
+			writew (readw (&i2c_base->con) | I2C_CON_STP, &i2c_base->con);
+			wait_for_bb ();
+			break;
+		}
+		if (status & I2C_STAT_ARDY) {
+			writew(I2C_STAT_ARDY, &i2c_base->stat);
+			break;
+		}
+		if (status & I2C_STAT_RRDY) {
+			res = 0;
+#if defined(CONFIG_OMAP243X) || defined(CONFIG_OMAP34XX) || \
+    defined(CONFIG_OMAP44XX)
+			readb(&i2c_base->data);
+#else
+			readw(&i2c_base->data);
+#endif
+			writew(I2C_STAT_RRDY, &i2c_base->stat);
+		}
 	}
+
+probe_exit:
 	flush_fifo();
 	writew (0, &i2c_base->cnt); /* don't allow any more data in...we don't want it.*/
 	writew(0xFFFF, &i2c_base->stat);
-- 
1.7.0.4

[U-Boot] [PATCH RFC 4/4] ARMV7: OMAP: I2C driver: Restructure i2c_probe function

[Heiko Schocher]

Hello Steve,

Steve Sakoman wrote:
> This patch removes the "magic number" delays and instead
> monitors state changes in the status register bits.
> 
> Signed-off-by: Steve Sakoman <steve.sakoman@linaro.org>
> ---
>  drivers/i2c/omap24xx_i2c.c |   41 ++++++++++++++++++++++++++++++-----------
>  1 files changed, 30 insertions(+), 11 deletions(-)

Applied to u-boot-i2c master

Thanks!

bye,
Heiko
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