[PATCH 1/1] Patch for I2C transmit overflow error

[PATCH 1/1] Patch for I2C transmit overflow error

[chandra shekhar]

Hi,

This patch is to fix I2C transmit overflow error.
I guess it should fix the OSK5912 error. I dont have the board to test it.

Regards,
Chandra Shekhar

Signed-off-by: Chandra Shekhar< x0044955@ti.com>
---
 drivers/i2c/busses/i2c-omap.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletion(-)

Index: linux-omap-2.6/drivers/i2c/busses/i2c-omap.c
===================================================================
--- linux-omap-2.6.orig/drivers/i2c/busses/i2c-omap.c	2008-08-07
19:30:00.000000000 +0530
+++ linux-omap-2.6/drivers/i2c/busses/i2c-omap.c	2008-08-07 19:30:19.000000000
+0530
@@ -661,6 +661,7 @@
 				}
 			}
 			omap_i2c_ack_stat(dev, stat & (OMAP_I2C_STAT_RRDY | OMAP_I2C_STAT_RDR));
+			continue;
 		}
 		if (stat & (OMAP_I2C_STAT_XRDY | OMAP_I2C_STAT_XDR)) {
 			u8 num_bytes = 1;
@@ -694,13 +695,14 @@
 				omap_i2c_write_reg(dev, OMAP_I2C_DATA_REG, w);
 			}
 			omap_i2c_ack_stat(dev, stat & (OMAP_I2C_STAT_XRDY | OMAP_I2C_STAT_XDR));
+			continue;
 		}
 		if (stat & OMAP_I2C_STAT_ROVR) {
 			dev_err(dev->dev, "Receive overrun\n");
 			dev->cmd_err |= OMAP_I2C_STAT_ROVR;
 		}
 		if (stat & OMAP_I2C_STAT_XUDF) {
-			dev_err(dev->dev, "Transmit overflow\n");
+			dev_err(dev->dev, "Transmit underflow\n");
 			dev->cmd_err |= OMAP_I2C_STAT_XUDF;
 		}
 	}

Re: [PATCH 1/1] Patch for I2C transmit overflow error

[David Brownell]

On Thursday 07 August 2008, chandra shekhar wrote:
> This patch is to fix I2C transmit overflow error.
> I guess it should fix the OSK5912 error. I dont have the board to test it.

Yes, it makes those error reports go away.
I'd say to merge this patch.

Re: [PATCH 1/1] Patch for I2C transmit overflow error

[Tony Lindgren]

* David Brownell <david-b@pacbell.net> [080808 03:37]:
> On Thursday 07 August 2008, chandra shekhar wrote:
> > This patch is to fix I2C transmit overflow error.
> > I guess it should fix the OSK5912 error. I dont have the board to test it.
> 
> Yes, it makes those error reports go away.
> I'd say to merge this patch.

Great, pushing today.

Tony

Re: [PATCH 1/1] Patch for I2C transmit overflow error

[David Brownell]

On Thursday 07 August 2008, Tony Lindgren wrote:
> * David Brownell <david-b@pacbell.net> [080808 03:37]:
> > On Thursday 07 August 2008, chandra shekhar wrote:
> > > This patch is to fix I2C transmit overflow error.
> > > I guess it should fix the OSK5912 error. I dont have the board to test it.
> > 
> > Yes, it makes those error reports go away.
> > I'd say to merge this patch.
> 
> Great, pushing today.

Further update:

 - I'm thinking it was either audio or USB that caused the boot
   problem, maybe old IDE code.  Disable a bunch of drivers and it
   booted enough for the watchdog thing to vanish.

 - I'm getting some i2c *underflow* errors reported, and it claimed
   write errors for one of the tps65010 registers at startup time.

Re: [PATCH 1/1] Patch for I2C transmit overflow error

[Jason Marini]

>>This patch is to fix I2C transmit overflow error.
>>I guess it should fix the OSK5912 error. I dont have the board to test it.
>
>Yes, it makes those error reports go away. I'd say to merge this patch.

Chandra, why would the transmit underflow (XDR) status sometimes be
set at the same time as the XRDY status?  Why would you want to ignore
XDR (using 'continue') if XRDY is set?

Thank you in advance for clearing this up for me.

-Jason Marini

Re: [PATCH 1/1] Patch for I2C transmit overflow error

[shekhar, chandra]

----- Original Message ----- 
From: "Jason Marini" <jason.marini@gmail.com>
To: <linux-omap@vger.kernel.org>
Sent: Wednesday, January 07, 2009 1:42 AM
Subject: Re: [PATCH 1/1] Patch for I2C transmit overflow error


>>>This patch is to fix I2C transmit overflow error.
>>>I guess it should fix the OSK5912 error. I dont have the board to test it.
>>
>>Yes, it makes those error reports go away. I'd say to merge this patch.
> 
> Chandra, why would the transmit underflow (XDR) status sometimes be
> set at the same time as the XRDY status? 

I dint say XDR and XRDY.
Its XDR and XUDF being set simultaneously. 

 Why would you want to ignore
> XDR (using 'continue') if XRDY is set?
> 

So i am not ignoring any XDR.  :)



> Thank you in advance for clearing this up for me.
> 
> -Jason Marini
> --
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Re: [PATCH 1/1] Patch for I2C transmit overflow error

[Jason Marini]

>
> ----- Original Message ----- From: "Jason Marini" <jason.marini@gmail.com>
> To: <linux-omap@vger.kernel.org>
> Sent: Wednesday, January 07, 2009 1:42 AM
> Subject: Re: [PATCH 1/1] Patch for I2C transmit overflow error
>
>
>>>> This patch is to fix I2C transmit overflow error.
>>>> I guess it should fix the OSK5912 error. I dont have the board to test
>>>> it.
>>>
>>> Yes, it makes those error reports go away. I'd say to merge this patch.
>>
>> Chandra, why would the transmit underflow (XDR) status sometimes be
>> set at the same time as the XRDY status?
>
> I dint say XDR and XRDY.
> Its XDR and XUDF being set simultaneously.
> Why would you want to ignore
>>
>> XDR (using 'continue') if XRDY is set?
>>
>
> So i am not ignoring any XDR.  :)

Whoops, jet lag.  Let me try again.  What I meant to ask was:

Why did you insert the 'continue' statements?  It seems as though a
valid transmit underflow or receive overrun message may be skipped
with this change.  Can you explain why the 'continue' statements are
necessary?

Sorry for the garbled original question.

-Jason

Re: [PATCH 1/1] Patch for I2C transmit overflow error

[shekhar, chandra]

----- Original Message ----- 
From: "Jason Marini" <jason.marini@gmail.com>
To: <linux-omap@vger.kernel.org>
Sent: Friday, January 09, 2009 6:49 PM
Subject: Re: [PATCH 1/1] Patch for I2C transmit overflow error


> >
>> ----- Original Message ----- From: "Jason Marini" <jason.marini@gmail.com>
>> To: <linux-omap@vger.kernel.org>
>> Sent: Wednesday, January 07, 2009 1:42 AM
>> Subject: Re: [PATCH 1/1] Patch for I2C transmit overflow error
>>
>>
>>>>> This patch is to fix I2C transmit overflow error.
>>>>> I guess it should fix the OSK5912 error. I dont have the board to test
>>>>> it.
>>>>
>>>> Yes, it makes those error reports go away. I'd say to merge this patch.
>>>
>>> Chandra, why would the transmit underflow (XDR) status sometimes be
>>> set at the same time as the XRDY status?
>>
>> I dint say XDR and XRDY.
>> Its XDR and XUDF being set simultaneously.
>> Why would you want to ignore
>>>
>>> XDR (using 'continue') if XRDY is set?
>>>
>>
>> So i am not ignoring any XDR.  :)
>
> Whoops, jet lag.  Let me try again.  What I meant to ask was:
>
> Why did you insert the 'continue' statements?  It seems as though a
> valid transmit underflow or receive overrun message may be skipped
> with this change.  Can you explain why the 'continue' statements are
> necessary?

A race condition arises where even xdr and xudf is simultaneously
generated. even if xdr is handled control used  to go to  xudf handler and we 
get the print and hence
error in return.  so it might happen that ur data is transferred
but u get error in return. in the aforementioned case simultaneous xdr and xudf 
were followed by xrdy.
If there is a genuine XUDF we will not get ardy.





>
> Sorry for the garbled original question.
>
> -Jason
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