Need help to fix some issues with the linux driver "i2c-gpio"

Need help to fix some issues with the linux driver "i2c-gpio"

[Matthias Zacharias]

Hello mailing list,
 
we have to use the linux driver "i2c-gpio" because the "i2c-at91" is
marked as "BROKEN" and for our application it can as well not be used.
 
Here a brief description of the application:
 
AT91SAM9261 based embedded system running kernel 2.6.25.4, with Atmel
and our own BSP patches. This system uses both SPI interfaces, one USART
(for console),  MMC, Sound on SPI and SSC, digital poti for contrast
control and the an chip Frambuffer for a monochrome LCD (QVGA).
 
On the TWI interface are attached: 
    the AT24C04 SMB EEPROM,   (@ 0x50)
    two LM84 Temperature sensors  (@ 0x18, 0x19)
    and the Infrared temperature sensor MLX90614 manfactured by
MELEXIS. (@ 0x5A)
Note: The LM84 sensors are not yet operated by the linux kernel.
 
Now the description of the issue we have with the I2C subsystem:
 
1. the EEPROM is working fine with "i2c-at91" and the "i2c-gpio"
modules
2. for IR-Sensor MLX90614, a hwmon class linux driver was implemented
by Linutronix on our demand. This driver works fine but delivers
sporadic the error message "i2c-adapter i2c-0: sendbytes: NAK bailout." 
(this message is thrown by the  "i2c-algo-bit" driver), or invalid
temperature values ( near 0xFFFF). The invalid temperature values and as
well the error message appear as reponse on bus timeout situations which
are not correctly handled by the linux driver. This we find out using a
I2C analyzer. In our opinion these issues come while the i2c
communication is disturbed by other tasks and/or interrupt service
routines (ISR) which extend the SMB clock over the permitted timeouts,
leaving the IR-Sensor in an undefined or erroneous (
http://dict.leo.org/ende?lp=ende&p=Ci4HO3kMAA&search=erroneous&trestr=0x8004
) state.
 
The address mentioned in the driver source "Haavard Skinnemoen
<hskinnemoen-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org>" invalid (unknown)
 
Please let us now if somebody can help in fixing the i2c-gpio, or give
us an other name who can help.
 
Thank you.
With best regards
 
 
Matthias Zacharias
Dipl.-Elektroingenieur (Univ) 
Projektleiter Entwicklung 



BMK professional electronics GmbH · Werner-von-Siemens-Str. 6 · D-86159
Augsburg
Tel: +49(0)821/20788-715· Fax: +49(0)821/20788-721· www.bmk-groupde

--------------------
BMK electronic solutions GmbH
Werner-von-Siemens-Str. 6, Eingang 18 f
D-86159 Augsburg
Tel. +49 (0) 821 / 207 88 - 700
Fax +49 (0) 821 / 207 88 - 721
info-zGrmWZs6xXT+aS/vkh9bjw@public.gmane.org
Geschäftsführer: Dipl.-oec. Alois Knöferle
Sitz: Augsburg
HR-Nr.: B21197
---------------------

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Need help to fix some issues with the linux driver "i2c-gpio"

[Matthias Zacharias]

** High Priority **

Hello mailing list,

we have to use the linux driver "i2c-gpio" because the "i2c-at91" is
marked as "BROKEN" and for our application it can as well not be used.

Here a brief description of the application:

AT91SAM9261 based embedded system running kernel 2.6.25.4, with Atmel
and our own BSP patches. This system uses both SPI interfaces, one USART
(for console),  MMC, Sound on SPI and SSC, digital poti for contrast
control and the an chip Frambuffer for a monochrome LCD (QVGA).

On the TWI interface are attached: 
    the AT24C04 SMB EEPROM,   (@ 0x50)
    two LM84 Temperature sensors  (@ 0x18, 0x19)
    and the Infrared temperature sensor MLX90614 manfactured by
MELEXIS. (@ 0x5A)
Note: The LM84 sensors are not yet operated by the linux kernel.

Now the description of the issue we have with the I2C subsystem:

1. the EEPROM is working fine with "i2c-at91" and the "i2c-gpio"
modules
2. for IR-Sensor MLX90614, a hwmon class linux driver was implemented
by Linutronix on our demand. This driver works fine but delivers
sporadic the error message "i2c-adapter i2c-0: sendbytes: NAK bailout." 
(this message is thrown by the  "i2c-algo-bit" driver), or invalid
temperature values ( near 0xFFFF). The invalid temperature values and as
well the error message appear as reponse on bus timeout situations which
are not correctly handled by the linux driver. This we find out using a
I2C analyzer. In our opinion these issues come while the i2c
communication is disturbed by other tasks and/or interrupt service
routines (ISR) which extend the SMB clock over the permitted timeouts,
leaving the IR-Sensor in an undefined or erroneous state.

The address mentioned in the driver source "Haavard Skinnemoen
<hskinnemoen-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org>" invalid (unknown)

Please let us now if somebody can help in fixing the i2c-gpio, or give
us an other name who can help.

Thank you.
With best regards


Matthias Zacharias
Dipl.-Elektroingenieur (Univ) 
Projektleiter Entwicklung 



BMK professional electronics GmbH · Werner-von-Siemens-Str. 6 · D-86159
Augsburg
Tel: +49(0)821/20788-715· Fax: +49(0)821/20788-721· www.bmk-groupde

--------------------
BMK electronic solutions GmbH
Werner-von-Siemens-Str. 6, Eingang 18 f
D-86159 Augsburg
Tel. +49 (0) 821 / 207 88 - 700
Fax +49 (0) 821 / 207 88 - 721
info-zGrmWZs6xXT+aS/vkh9bjw@public.gmane.org
Geschäftsführer: Dipl.-oec. Alois Knöferle
Sitz: Augsburg
HR-Nr.: B21197
---------------------

Diese E-mail kann vertrauliche Informationen enthalten. Falls Sie diese
E-Mail irrtümlich erhalten haben, informieren Sie bitte unverzüglich den
Absender und löschen Sie diese E-Mail von jedem Rechner, auch von den
Mailservern. Jede Verbreitung des Inhalts, auch die teilweise
Verbreitung, ist in diesem Fall untersagt. Außer bei Vorsatz oder grober
Fahrlässigkeit schliessen wir jegliche Haftung für Verluste oder Schäden
aus, die durch Viren befallene Software oder E-Mails verursacht werden.

This e-mail may contain confidential information. If you received this
e-mail in error, please contact the sender and delete this e-mail from
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misconduct we accept no liability for any loss or damage caused by
software or e-mail viruses.

Re: Need help to fix some issues with the linux driver "i2c-gpio"

[Bill Gatliff]

Is the i2c clock speed in spec with the slave part(s)?

I have seen weird things happen when the clock speed is wrong,
especially when it's too fast...



b.g.
-- 
Bill Gatliff
bgat-uPd5UNENI//N9NzbbXoYwQ@public.gmane.org

Re: Need help to fix some issues with the linux driver "i2c-gpio"

[Jean Delvare]

Hi Matthias,

On Tue, 30 Nov 2010 11:26:22 +0100, Matthias Zacharias wrote:
> ** High Priority **

There is no such thing here. People on this list reply to help requests
on their free time. This is best effort, with zero guarantee.

> we have to use the linux driver "i2c-gpio" because the "i2c-at91" is
> marked as "BROKEN" and for our application it can as well not be used.
> 
> Here a brief description of the application:
> 
> AT91SAM9261 based embedded system running kernel 2.6.25.4, with Atmel
> and our own BSP patches. This system uses both SPI interfaces, one USART
> (for console),  MMC, Sound on SPI and SSC, digital poti for contrast
> control and the an chip Frambuffer for a monochrome LCD (QVGA).
> 
> On the TWI interface are attached: 
>     the AT24C04 SMB EEPROM,   (@ 0x50)
>     two LM84 Temperature sensors  (@ 0x18, 0x19)
>     and the Infrared temperature sensor MLX90614 manfactured by
> MELEXIS. (@ 0x5A)
> Note: The LM84 sensors are not yet operated by the linux kernel.
> 
> Now the description of the issue we have with the I2C subsystem:
> 
> 1. the EEPROM is working fine with "i2c-at91" and the "i2c-gpio"
> modules

So at least the i2c-gpio driver isn't totally broken on your hardware.

> 2. for IR-Sensor MLX90614, a hwmon class linux driver was implemented
> by Linutronix on our demand. This driver works fine but delivers
> sporadic the error message "i2c-adapter i2c-0: sendbytes: NAK bailout." 
> (this message is thrown by the  "i2c-algo-bit" driver), or invalid
> temperature values ( near 0xFFFF). The invalid temperature values and as
> well the error message appear as reponse on bus timeout situations which
> are not correctly handled by the linux driver. This we find out using a
> I2C analyzer. In our opinion these issues come while the i2c
> communication is disturbed by other tasks and/or interrupt service
> routines (ISR) which extend the SMB clock over the permitted timeouts,
> leaving the IR-Sensor in an undefined or erroneous state.

It's difficult to answer here without seeing the source code of the
MLX90614 driver. What I can say is that values "near 0xFFFF" look like
uncaught (negative) error codes carelessly cast to u16. So you should
ensure that your driver properly deals with errors returned by the i2c
layer (i2c_transfer and i2c_smbus_*). And if such errors happen, you
should print them so that you see what exactly is going on and when.

If the EEPROM works fine, it may depend on the transaction types. I
can't comment further because you didn't tell us which driver you were
using (eeprom or at24). But it would be interesting to see which
transactions fail, and if there is a pattern.

For your investigation, you may be interested in backporting (the
i2c-algo-bit-part of) the following patch:
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=97140342e69d479a3ad82bfd4c154c0b08fe3eea

If you hit unexpected timeout conditions, you may want to try again
after backporting this fix:
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=0cdba07bb23cdd3e0d64357ec3d983e6b75e541f

More generally, you may want to change the timeout value and see if it
helps - although the default of 100 ms seem reasonable to me.

Note that i2c-algo-bit is CPU-driven. It doesn't sleep, so it shouldn't
be preempted by regular code, but nothing can be done against
interrupts. I see that the MLX90614 has a very short timeout when SCL
is high (45 to 55 us), so receiving an interrupt in this state could
indeed be an issue. You may want to try disabling interrupts before
raising SCL (except at the end of the transaction, of course) in
i2c-algo-bit.

And, as Bill already underlined, you have to ensure that you're running
the bus at the right frequency. The MLX90614 is an SMBus compliant
device so it wants a clock between 10 and 100 kHz. This means a udelay
value between 5 and 50.

> The address mentioned in the driver source "Haavard Skinnemoen
> <hskinnemoen-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org>" invalid (unknown)

I presume Haavard left Atmel meanwhile. Not much we can do about that,
except removing his address from the source tree (I will do.)

-- 
Jean Delvare
http://khali.linux-fr.org/wishlist.html

Antw: Re: Need help to fix some issues with the linux driver "i2c-gpio"

[Matthias Zacharias]

Thank you for the fast reply.
 
I checked the clock speed, It can be changed in the specified limits
for MLX90614 with similar results in the data output.
 
Using an I2C analyzer I was able to see that SCL stretching occures on
unpredictable times. If these SCL stretching is on specific point in the
communication process or match the one of the SMbus timeout condition
unpredictable data is output, with out any error from the I2C subsystem.
Only the "i2c-adapter i2c-0: sendbytes: NAK bailout." message is
correctly thrown.
 
best regards
Matthias Zacharias
matthias.zacharias-zGrmWZs6xXT+aS/vkh9bjw@public.gmane.org 

>>> Bill Gatliff <bgat-uPd5UNENI//N9NzbbXoYwQ@public.gmane.org> 30.11.2010 17:44 >>>
Is the i2c clock speed in spec with the slave part(s)?

I have seen weird things happen when the clock speed is wrong,
especially when it's too fast...



b.g.
-- 
Bill Gatliff
bgat-uPd5UNENI//N9NzbbXoYwQ@public.gmane.org

--------------------
BMK electronic solutions GmbH
Werner-von-Siemens-Str. 6, Eingang 18 f
D-86159 Augsburg
Tel. +49 (0) 821 / 207 88 - 700
Fax +49 (0) 821 / 207 88 - 721
info-zGrmWZs6xXT+aS/vkh9bjw@public.gmane.org
Geschäftsführer: Dipl.-oec. Alois Knöferle
Sitz: Augsburg
HR-Nr.: B21197
---------------------

Diese E-mail kann vertrauliche Informationen enthalten. Falls Sie diese
E-Mail irrtümlich erhalten haben, informieren Sie bitte unverzüglich den
Absender und löschen Sie diese E-Mail von jedem Rechner, auch von den
Mailservern. Jede Verbreitung des Inhalts, auch die teilweise
Verbreitung, ist in diesem Fall untersagt. Außer bei Vorsatz oder grober
Fahrlässigkeit schliessen wir jegliche Haftung für Verluste oder Schäden
aus, die durch Viren befallene Software oder E-Mails verursacht werden.

This e-mail may contain confidential information. If you received this
e-mail in error, please contact the sender and delete this e-mail from
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software or e-mail viruses.

Antw: Re: Need help to fix some issues with the linux driver "i2c-gpio"

[Matthias Zacharias]

Hi Jean,
 
thank you for the fast reply.
 
See further comments in your reply:

>>> Jean Delvare <khali-PUYAD+kWke1g9hUCZPvPmw@public.gmane.org> 30.11.2010 18:21 >>>
Hi Matthias,

On Tue, 30 Nov 2010 11:26:22 +0100, Matthias Zacharias wrote:
>> ** High Priority **

> There is no such thing here. People on this list reply to help
requests
> on their free time. This is best effort, with zero guarantee.
 
Ok, I know this, and am happy for getting your response  so quickly.

>> we have to use the linux driver "i2c-gpio" because the "i2c-at91"
is
>> marked as "BROKEN" and for our application it can as well not be
used.
>> 
>> Here a brief description of the application:
>> 
>> AT91SAM9261 based embedded system running kernel 2.6.25.4, with
Atmel
>> and our own BSP patches. This system uses both SPI interfaces, one
USART
>> (for console),  MMC, Sound on SPI and SSC, digital poti for
contrast
>> control and the an chip Frambuffer for a monochrome LCD (QVGA).
>> 
>> On the TWI interface are attached: 
>>     the AT24C04 SMB EEPROM,   (@ 0x50)
>>     two LM84 Temperature sensors  (@ 0x18, 0x19)
>>     and the Infrared temperature sensor MLX90614 manfactured by
>> MELEXIS. (@ 0x5A)
>> Note: The LM84 sensors are not yet operated by the linux kernel.
>> 
>> Now the description of the issue we have with the I2C subsystem:
>> 
>> 1. the EEPROM is working fine with "i2c-at91" and the "i2c-gpio"
>> modules

> So at least the i2c-gpio driver isn't totally broken on your
hardware.
 
No it works, but with unpredictable results in the data output
(measured temperature)

>> 2. for IR-Sensor MLX90614, a hwmon class linux driver was
implemented
>> by Linutronix on our demand. This driver works fine but delivers
>> sporadic the error message "i2c-adapter i2c-0: sendbytes: NAK
bailout." 
>> (this message is thrown by the  "i2c-algo-bit" driver), or invalid
>> temperature values ( near 0xFFFF). The invalid temperature values
and as
>> well the error message appear as reponse on bus timeout situations
which
>> are not correctly handled by the linux driver. This we find out
using a
>> I2C analyzer. In our opinion these issues come while the i2c
>> communication is disturbed by other tasks and/or interrupt service
>> routines (ISR) which extend the SMB clock over the permitted
timeouts,
>> leaving the IR-Sensor in an undefined or erroneous state.

> It's difficult to answer here without seeing the source code of the
> MLX90614 driver. What I can say is that values "near 0xFFFF" look
like
> uncaught (negative) error codes carelessly cast to u16. So you
should
> ensure that your driver properly deals with errors returned by the
i2c
> layer (i2c_transfer and i2c_smbus_*). And if such errors happen, you
> should print them so that you see what exactly is going on and when.

I can provide the sources for the MLX90614 driver, but I think it is
not a good ideea to attach it to this E-Mail.

> If the EEPROM works fine, it may depend on the transaction types. I
> can't comment further because you didn't tell us which driver you
were
> using (eeprom or at24). But it would be interesting to see which
> transactions fail, and if there is a pattern.

I access the eeprom as generic i2c device (file pointer to i2c-0)
without usage of any specific driver.

> For your investigation, you may be interested in backporting (the
> i2c-algo-bit-part of) the following patch:
>
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=97140342e69d479a3ad82bfd4c154c0b08fe3eea


> If you hit unexpected timeout conditions, you may want to try again
> after backporting this fix:
>
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=0cdba07bb23cdd3e0d64357ec3d983e6b75e541f


At first I'll try the suggested patches.

> More generally, you may want to change the timeout value and see if
it
> helps - although the default of 100 ms seem reasonable to me.
 
changing the timeout value has no 
visible effect on the systems
behavoir.

> Note that i2c-algo-bit is CPU-driven. It doesn't sleep, so it
shouldn't
> be preempted by regular code, but nothing can be done against
> interrupts. I see that the MLX90614 has a very short timeout when
SCL
> is high (45 to 55 us), so receiving an interrupt in this state could
> indeed be an issue. You may want to try disabling interrupts before
> raising SCL (except at the end of the transaction, of course) in
> i2c-algo-bit.

Please give me an example how the disable interrupts as you suggest.
In the i2c-algo-bits there is used the "bit_dbg" makro to print some
debug messages to ksys. Removing the makros wich where placed on the
main execution line (not on for error messages) helps to get a better
behavoir: SCL stretching occure on better reproducable communication
times.

> And, as Bill already underlined, you have to ensure that you're
running
> the bus at the right frequency. The MLX90614 is an SMBus compliant
> device so it wants a clock between 10 and 100 kHz. This means a
udelay
> value between 5 and 50.

I checked the clock speed, It can be changed in the specified limits
for MLX90614 with similar results in the data output. 
Using an I2C analyzer I was able to see that SCL stretching occures on
unpredictable times. If these SCL stretching is on specific point in the
communication process or match the one of the SMbus timeout conditions
(2 different timeout values) unpredictable data is output, with out any
error from the I2C subsystem. Only the "i2c-adapter i2c-0: sendbytes:
NAK bailout." message is correctly thrown.

I can provide screeshots which ilustrate the behavoir. How can I make
these sceenshots available for you?

>> The address mentioned in the driver source "Haavard Skinnemoen
>> <hskinnemoen-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org>" invalid (unknown)

> I presume Haavard left Atmel meanwhile. Not much we can do about
that,
> except removing his address from the source tree (I will do.)
the last entry @vger.kernel.org was in 2007
-- 
Jean Delvare
http://khali.linux-fr.org/wishlist.html 

best regards
Matthias Zacharias
matthias.zacharias-zGrmWZs6xXT+aS/vkh9bjw@public.gmane.org 


 


--------------------
BMK electronic solutions GmbH
Werner-von-Siemens-Str. 6, Eingang 18 f
D-86159 Augsburg
Tel. +49 (0) 821 / 207 88 - 700
Fax +49 (0) 821 / 207 88 - 721
info-zGrmWZs6xXT+aS/vkh9bjw@public.gmane.org
Geschäftsführer: Dipl.-oec. Alois Knöferle
Sitz: Augsburg
HR-Nr.: B21197
---------------------

Diese E-mail kann vertrauliche Informationen enthalten. Falls Sie diese
E-Mail irrtümlich erhalten haben, informieren Sie bitte unverzüglich den
Absender und löschen Sie diese E-Mail von jedem Rechner, auch von den
Mailservern. Jede Verbreitung des Inhalts, auch die teilweise
Verbreitung, ist in diesem Fall untersagt. Außer bei Vorsatz oder grober
Fahrlässigkeit schliessen wir jegliche Haftung für Verluste oder Schäden
aus, die durch Viren befallene Software oder E-Mails verursacht werden.

This e-mail may contain confidential information. If you received this
e-mail in error, please contact the sender and delete this e-mail from
your computer, including your mailservers. Any dissemination, even
partly, is prohibited. Except in case of gross negligence or wilful
misconduct we accept no liability for any loss or damage caused by
software or e-mail viruses.

Re: Need help to fix some issues with the linux driver "i2c-gpio"

[Jean Delvare]

Hi Matthias,

On Wed, 01 Dec 2010 11:01:17 +0100, Matthias Zacharias wrote:
> >>> Jean Delvare <khali-PUYAD+kWke1g9hUCZPvPmw@public.gmane.org> 30.11.2010 18:21 >>>
> > It's difficult to answer here without seeing the source code of the
> > MLX90614 driver. What I can say is that values "near 0xFFFF" look
> > like uncaught (negative) error codes carelessly cast to u16. So you
> > should ensure that your driver properly deals with errors returned
> > by the i2c layer (i2c_transfer and i2c_smbus_*). And if such errors
> > happen, you should print them so that you see what exactly is going
> > on and when.
> 
> I can provide the sources for the MLX90614 driver, but I think it is
> not a good ideea to attach it to this E-Mail.

If the source code is publicly visible somewhere, you can point us to
that location. If not, maybe this is the right time to publish it ;) Or
you can send it to me privately.

BTW, it would be very interesting to see if you can get a MLX90614 chip
to work with this driver on another system with a different I2C or
SMBus master.

> > If the EEPROM works fine, it may depend on the transaction types. I
> > can't comment further because you didn't tell us which driver you
> > were using (eeprom or at24). But it would be interesting to see
> > which transactions fail, and if there is a pattern.
> 
> I access the eeprom as generic i2c device (file pointer to i2c-0)
> without usage of any specific driver.

Which system calls and transaction types are you using?

Did you try accessing the MLX90614 the same way?

> > Note that i2c-algo-bit is CPU-driven. It doesn't sleep, so it
> > shouldn't be preempted by regular code, but nothing can be done
> > against interrupts. I see that the MLX90614 has a very short
> > timeout when SCL is high (45 to 55 us), so receiving an interrupt
> > in this state could indeed be an issue. You may want to try
> > disabling interrupts before raising SCL (except at the end of the
> > transaction, of course) in i2c-algo-bit.
> 
> Please give me an example how the disable interrupts as you suggest.

Err. I thought there was a kernel function for that, but apparently I
was wrong. Well this could be done in asm but I don't think you want to
try that.

Maybe you can do something with spin_lock_irqsave() and
spin_unlock_irqrestore() around the critical sections, I'm not sure.

> In the i2c-algo-bits there is used the "bit_dbg" makro to print some
> debug messages to ksys. Removing the makros wich where placed on the
> main execution line (not on for error messages) helps to get a better
> behavoir: SCL stretching occure on better reproducable communication
> times.

Err, are you by any chance running a kernel built with
CONFIG_I2C_DEBUG_ALGO=y, and have set i2c_debug to 2 or more? This
could explain your problems, at least in part. i2c-algo-bit is quite
verbose in the kernel logs when debugging level is set to 2 or more,
and writing the log to the disk is adding a lot of latency to the
system.

Unfortunately this is one case where enabling debugging to better
understand what is going on also affects what is going on. As you have
an external bus analyzer, it's better to not enable debugging in
i2c-algo-bit, or at least not beyond level 1.

When CONFIG_I2C_DEBUG_ALGO isn't set, bit_dbg() is a no-op so it
certainly can't affect you in any way.

> > And, as Bill already underlined, you have to ensure that you're
> > running the bus at the right frequency. The MLX90614 is an SMBus
> > compliant device so it wants a clock between 10 and 100 kHz. This
> > means a udelay value between 5 and 50.
> 
> I checked the clock speed, It can be changed in the specified limits
> for MLX90614 with similar results in the data output. 
> Using an I2C analyzer I was able to see that SCL stretching occures on
> unpredictable times. If these SCL stretching is on specific point in the
> communication process or match the one of the SMbus timeout conditions
> (2 different timeout values) unpredictable data is output, with out any
> error from the I2C subsystem. Only the "i2c-adapter i2c-0: sendbytes:
> NAK bailout." message is correctly thrown.

Question is whether the SCL line is stretched by the master or by the
slave. Both are allowed to do it to a certain point.

Does stretching happen on SCL high, or SCL low, or both?

If the stretching is done by the master, then you may search for
interrupt sources on your system. Maybe you have a misbehaving driver
or device on your system which causes repeated and long interruptions.
Making these interruptions shorter (e.g. by moving the real work to a
workqueue) would then help.

> I can provide screeshots which ilustrate the behavoir. How can I make
> these sceenshots available for you?

Either put it on some publicly available web server if you have one
at hand; or send them to me by mail privately.

> > I presume Haavard left Atmel meanwhile. Not much we can do about
> > that, except removing his address from the source tree (I will
> > do.)
> the last entry @vger.kernel.org was in 2007

Not true. He posted until September 2010:
http://marc.info/?l=linux-kernel&m=128498842805216&w=2

Said post confirms that he left Atmel, BTW. Too bad he did not remove
or update his address in the tree at that time.

-- 
Jean Delvare

Antw: Re: Need help to fix some issues with the linux driver "i2c-gpio"

[Matthias Zacharias]

Hi Jean,

>>> Jean Delvare <khali-PUYAD+kWke1g9hUCZPvPmw@public.gmane.org> schrieb am Donnerstag, 2.
Dezember 2010 um
17:23 in Nachricht <20101202172322.43ea4698-R0o5gVi9kd7kN2dkZ6Wm7A@public.gmane.org>:
> Hi Matthias,
> 
> On Wed, 01 Dec 2010 11:01:17 +0100, Matthias Zacharias wrote:
>> >>> Jean Delvare <khali-PUYAD+kWke1g9hUCZPvPmw@public.gmane.org> 30.11.2010 18:21 >>>
>> > It's difficult to answer here without seeing the source code of
the
>> > MLX90614 driver. What I can say is that values "near 0xFFFF" look
>> > like uncaught (negative) error codes carelessly cast to u16. So
you
>> > should ensure that your driver properly deals with errors
returned
>> > by the i2c layer (i2c_transfer and i2c_smbus_*). And if such
errors
>> > happen, you should print them so that you see what exactly is
going
>> > on and when.
>> 
>> I can provide the sources for the MLX90614 driver, but I think it
is
>> not a good ideea to attach it to this E-Mail.
> 
> If the source code is publicly visible somewhere, you can point us
to
> that location. If not, maybe this is the right time to publish it ;)
Or
> you can send it to me privately.

Where is a good place to publish the MLX90614 driver?
> 
> BTW, it would be very interesting to see if you can get a MLX90614
chip
> to work with this driver on another system with a different I2C or
> SMBus master.

Any suggestion how to do that? I don't know how to get other hardware
which has an accessible SMBus to connect the MLX90614 directly.
> 
>> > If the EEPROM works fine, it may depend on the transaction types.
I
>> > can't comment further because you didn't tell us which driver you
>> > were using (eeprom or at24). But it would be interesting to see
>> > which transactions fail, and if there is a pattern.
>> 
>> I access the eeprom as generic i2c device (file pointer to i2c-0)
>> without usage of any specific driver.
> 
> Which system calls and transaction types are you using?

The MLX90614 uses now only the i2c_smbus_xfer(..) transaction to read
from the SMBus. But I think the MLX90614 driver must be extended to be
able to write configuration data (Word) on SMBus device as well.

> 
> Did you try accessing the MLX90614 the same way?

The MLX90614 is accessed as a hwmon device using the new device model
> 
>> > Note that i2c-algo-bit is CPU-driven. It doesn't sleep, so it
>> > shouldn't be preempted by regular code, but nothing can be done
>> > against interrupts. I see that the MLX90614 has a very short
>> > timeout when SCL is high (45 to 55 us), so receiving an interrupt
>> > in this state could indeed be an issue. You may want to try
>> > disabling interrupts before raising SCL (except at the end of the
>> > transaction, of course) in i2c-algo-bit.
>> 
>> Please give me an example how the disable interrupts as you
suggest.
> 
> Err. I thought there was a kernel function for that, but apparently
I
> was wrong. Well this could be done in asm but I don't think you want
to
> try that.
> 
> Maybe you can do something with spin_lock_irqsave() and
> spin_unlock_irqrestore() around the critical sections, I'm not sure.
> 

I have no experience with spin_lock's, don't know how to use them. If
you have a good example please point me to it.

>> In the i2c-algo-bits there is used the "bit_dbg" makro to print
some
>> debug messages to ksys. Removing the makros wich where placed on
the
>> main execution line (not on for error messages) helps to get a
better
>> behavoir: SCL stretching occure on better reproducable
communication
>> times.
> 
> Err, are you by any chance running a kernel built with
> CONFIG_I2C_DEBUG_ALGO=y, and have set i2c_debug to 2 or more? This
> could explain your problems, at least in part. i2c-algo-bit is quite
> verbose in the kernel logs when debugging level is set to 2 or more,
> and writing the log to the disk is adding a lot of latency to the
> system.
>

Yes, I made some tests with CONFIG_I2C_DEBUG_ALGO=y it it was a
disaster, notthing runs. I get only a bunch of errors but notthing
us
eful.

> 
> Unfortunately this is one case where enabling debugging to better
> understand what is going on also affects what is going on. As you
have
> an external bus analyzer, it's better to not enable debugging in
> i2c-algo-bit, or at least not beyond level 1.
> 
> When CONFIG_I2C_DEBUG_ALGO isn't set, bit_dbg() is a no-op so it
> certainly can't affect you in any way.
> 
I don't know how the compiler do handle the bit_dbg() makro, but I can
see the difference if the bit_dbg() call where included in the code or
not,  also if  CONFIG_I2C_DEBUG_ALGO was not set. 
>
>> > And, as Bill already underlined, you have to ensure that you're
>> > running the bus at the right frequency. The MLX90614 is an SMBus
>> > compliant device so it wants a clock between 10 and 100 kHz. This
>> > means a udelay value between 5 and 50.
>> 
>> I checked the clock speed, It can be changed in the specified
limits
>> for MLX90614 with similar results in the data output. 
>> Using an I2C analyzer I was able to see that SCL stretching occures
on
>> unpredictable times. If these SCL stretching is on specific point in
the
>> communication process or match the one of the SMbus timeout
conditions
>> (2 different timeout values) unpredictable data is output, with out
any
>> error from the I2C subsystem. Only the "i2c-adapter i2c-0:
sendbytes:
>> NAK bailout." message is correctly thrown.
> 
> Question is whether the SCL line is stretched by the master or by
the
> slave. Both are allowed to do it to a certain point.
> 
in the board settings I configure the SCL signal as output only to
avoid that SCL streching can be done by the SMBus slaves.
>
> Does stretching happen on SCL high, or SCL low, or both?
> 
The streching occures on both levels at un predictable times
>
> If the stretching is done by the master, then you may search for
> interrupt sources on your system. Maybe you have a misbehaving
driver
> or device on your system which causes repeated and long
interruptions.
> Making these interruptions shorter (e.g. by moving the real work to
a
> workqueue) would then help.
> 
I have no ideea how to find a missbehaving driver, if any?
>
>> I can provide screeshots which ilustrate the behavoir. How can I
make
>> these sceenshots available for you?
> 
> Either put it on some publicly available web server if you have one
> at hand; or send them to me by mail privately.
> 
I had an account @drop.io if it is still active I put the screenshots
there and point you that place.
>
>> > I presume Haavard left Atmel meanwhile. Not much we can do about
>> > that, except removing his address from the source tree (I will
>> > do.)
>> the last entry @vger.kernel.org was in 2007
> 
> Not true. He posted until September 2010:
> http://marc.info/?l=linux-kernel&m=128498842805216&w=2 
> 
> Said post confirms that he left Atmel, BTW. Too bad he did not
remove
> or update his address in the tree at that time.

best regards
matthias

--------------------
BMK electronic solutions GmbH
Werner-von-Siemens-Str. 6, Eingang 18 f
D-86159 Augsburg
Tel. +49 (0) 821 / 207 88 - 700
Fax +49 (0) 821 / 207 88 - 721
info-zGrmWZs6xXT+aS/vkh9bjw@public.gmane.org
Geschäftsführer: Dipl.-oec. Alois Knöferle
Sitz: Augsburg
HR-Nr.: B21197
---------------------

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software or e-mail viruses.

Re: Need help to fix some issues with the linux driver "i2c-gpio"

[Jean Delvare]

Hi Matthias,

On Mon, 06 Dec 2010 09:44:53 +0100, Matthias Zacharias wrote:
> > On Wed, 01 Dec 2010 11:01:17 +0100, Matthias Zacharias wrote:
> >> I can provide the sources for the MLX90614 driver, but I think it
> >> is not a good ideea to attach it to this E-Mail.
> > 
> > If the source code is publicly visible somewhere, you can point us
> > to that location. If not, maybe this is the right time to publish
> > it ;) Or you can send it to me privately.
> 
> Where is a good place to publish the MLX90614 driver?

The lm-sensors list would be a good place, as indicated in section
"HARDWARE MONITORING" of file MAINTAINERS in the kernel source tree. If
you intend to get this driver in the upstream kernel tree, you'll have
to post it there sooner or later anyway (even though the device is more
of a temperature sensor than an actual hardware monitoring chip.)

> > BTW, it would be very interesting to see if you can get a MLX90614
> > chip to work with this driver on another system with a different
> > I2C or SMBus master.
> 
> Any suggestion how to do that? I don't know how to get other hardware
> which has an accessible SMBus to connect the MLX90614 directly.

Some boards have SMBus pins accessible to connect external devices.
Otherwise you need a soldering iron and basic electronics skills and
equipment.

> >> (...)
> >> I access the eeprom as generic i2c device (file pointer to i2c-0)
> >> without usage of any specific driver.
> > 
> > Which system calls and transaction types are you using?
> 
> The MLX90614 uses now only the i2c_smbus_xfer(..) transaction to read
> from the SMBus. But I think the MLX90614 driver must be extended to be
> able to write configuration data (Word) on SMBus device as well.

My question was related to your access to the EEPROM access, not the
MLX90614. Besides, i2c_smbus_xfer() is a generic function for all SMBus
transaction types, so you didn't completely answer my question. Which
SMBus transaction types are you asking i2c_smbus_xfer() for?

> > Did you try accessing the MLX90614 the same way?
> 
> The MLX90614 is accessed as a hwmon device using the new device model

I know that. My question was, did you try an alternative way? For
example you could use the i2cget command line tool (part of i2c-tools)
for user-space access. It would be interesting to see if it makes a
difference.

> > (...)
> > Err. I thought there was a kernel function for that, but apparently
> > I was wrong. Well this could be done in asm but I don't think you want
> > to try that.
> > 
> > Maybe you can do something with spin_lock_irqsave() and
> > spin_unlock_irqrestore() around the critical sections, I'm not sure.
> 
> I have no experience with spin_lock's, don't know how to use them. If
> you have a good example please point me to it.

I don't have any experience with spin locks either (at least none of
the driver I wrote ever used one) but with over 4000 calls to this
function throughout the kernel source tree, it shouldn't be difficult
to find an example you can follow.

> > (...)
> > When CONFIG_I2C_DEBUG_ALGO isn't set, bit_dbg() is a no-op so it
> > certainly can't affect you in any way.
> > 
> I don't know how the compiler do handle the bit_dbg() makro, but I can
> see the difference if the bit_dbg() call where included in the code or
> not,  also if  CONFIG_I2C_DEBUG_ALGO was not set.

This is highly unlikely, unless you modified the driver source code.
bit_dbg is defined with:

#ifdef DEBUG
#define bit_dbg(level, dev, format, args...) \
	do { \
		if (i2c_debug >= level) \
			dev_dbg(dev, format, ##args); \
	} while (0)
#else
#define bit_dbg(level, dev, format, args...) \
	do {} while (0)
#endif /* DEBUG */

And DEBUG is only set if CONFIG_I2C_DEBUG_ALGO=y. So bit_dbg() is a
no-op when CONFIG_I2C_DEBUG_ALGO isn't set.

As a matter of fact, I just tried removing all calls to bit_dbg() and
i2c-algo-bit.o is unchanged, as I expected. So either you messed up
your testing, or your compiler is seriously broken.

> > Question is whether the SCL line is stretched by the master or by
> > the slave. Both are allowed to do it to a certain point.
>
> in the board settings I configure the SCL signal as output only to
> avoid that SCL streching can be done by the SMBus slaves.

Oh my! You shot yourself in the foot!

How do you expect _slaves_ to change their behavior just because you
said your I2C master to not pay attention to clock stretching? If
slaves want to stretch the clock line, they will. The MLX90614
datasheet isn't mentioning clock stretching, but that doesn't mean the
device is not doing exactly that.

You really want a bidirectional SCL on the master side, otherwise
reliability cannot be guaranteed. In fact, i2c-algo-bit with no SCL read
callback is not I2C-compliant. It's just a hack because sometimes we
have no other way, but in real systems you really don't want to do
that. Maybe I should make i2c-algo-bit complain when SCL read callback
is missing, to make it more obvious.

So please fix this, set a proper callback for SCL read. This alone
might fix your problem.

> > Does stretching happen on SCL high, or SCL low, or both?
>
> The streching occures on both levels at un predictable times.

This would be on the master side then. Slaves can stretch the clock
line by holding it down, but they can't prevent it from going down if
the master pulls it low, so they can't stretch the high part of the
clock cycle.

> > If the stretching is done by the master, then you may search for
> > interrupt sources on your system. Maybe you have a misbehaving
> > driver or device on your system which causes repeated and long
> > interruptions. Making these interruptions shorter (e.g. by moving
> > the real work to a workqueue) would then help.
>
> I have no ideea how to find a missbehaving driver, if any?

This isn't trivial. You can try unloading each driver sequentially and
see if things get better when one driver is missing. You can also check
in /proc/interrupts if any value is increasing particularly fast, or if
you can find a correlation between SCL problems and a particular
interrupt.

Some kernel debug options might be helpful here, such as
CONFIG_DETECT_SOFTLOCKUP and CONFIG_LATENCYTOP, and maybe others. I'm
not too familiar with this.

-- 
Jean Delvare
http://khali.linux-fr.org/wishlist.html

Antw: Re: Need help to fix some issues with the linux driver "i2c-gpio"

[Matthias Zacharias]

Hi Jean,

>>> Jean Delvare <khali-PUYAD+kWke1g9hUCZPvPmw@public.gmane.org> schrieb am Montag, 6. Dezember
2010 um 11:25
in Nachricht <20101206112557.3dc8ffe3-R0o5gVi9kd7kN2dkZ6Wm7A@public.gmane.org>
> Hi Matthias,
> 
> On Mon, 06 Dec 2010 09:44:53 +0100, Matthias Zacharias wrote:
>> > On Wed, 01 Dec 2010 11:01:17 +0100, Matthias Zacharias wrote:
>> >> I can provide the sources for the MLX90614 driver, but I think
it
>> >> is not a good ideea to attach it to this E-Mail.
>> > 
>> > If the source code is publicly visible somewhere, you can point
us
>> > to that location. If not, maybe this is the right time to publish
>> > it ;) Or you can send it to me privately.
>> 
>> Where is a good place to publish the MLX90614 driver?
> 
> The lm-sensors list would be a good place, as indicated in section
> "HARDWARE MONITORING" of file MAINTAINERS in the kernel source tree.
If
> you intend to get this driver in the upstream kernel tree, you'll
have
> to post it there sooner or later anyway (even though the device is
more
> of a temperature sensor than an actual hardware monitoring chip.)
> 
>> > BTW, it would be very interesting to see if you can get a
MLX90614
>> > chip to work with this driver on another system with a different
>> > I2C or SMBus master.
>> Hi, jean
>> Any suggestion how to do that? I don't know how to get other
hardware
>> which has an accessible SMBus to connect the MLX90614 directly.
> 
> Some boards have SMBus pins accessible to connect external devices.
> Otherwise you need a soldering iron and basic electronics skills and
> equipment.
> 
>> >> (...)
>> >> I access the eeprom as generic i2c device (file pointer to
i2c-0)
>> >> without usage of any specific driver.
>> > 
>> > Which system calls and transaction types are you using?
>> 
>> The MLX90614 uses now only the i2c_smbus_xfer(..) transaction to
read
>> from the SMBus. But I think the MLX90614 driver must be extended to
be
>> able to write configuration data (Word) on SMBus device as well.
> 
> My question was related to your access to the EEPROM access, not the
> MLX90614. Besides, i2c_smbus_xfer() is a generic function for all
SMBus
> transaction types, so you didn't completely answer my question.
Which
> SMBus transaction types are you asking i2c_smbus_xfer() for?
> 

Only read_word() with PEC and write_word() 

>> > Did you try accessing the MLX90614 the same way?
>> 
>> The MLX90614 is accessed as a hwmon device using the new device
model
> 
> I know that. My question was, did you try an alternative way? For
> example you could use the i2cget command line tool (part of
i2c-tools)
> for user-space access. It would be interesting to see if it makes a
> difference.
> 

I don't get the i2c-tools compiled for my armv5l platform. So can't try
to work with these tools. Do you know how to get the i2c-tools working
on an ARM9 microcontroller. I think it's a problem of setting the right
configuration.

>> > (...)
>> > Err. I thought there was a kernel function for that, but
apparently
>> > I was wrong. Well this could be done in asm but I don't think you
want
>> > to try that.
>> > 
>> > Maybe you can do something with spin_lock_irqsave() and
>> > spin_unlock_irqrestore() around the critical sections, I'm not
sure.
>> 
>> I have no experience with spin_lock's, don't know how to use them.
If
>> you have a good example please point me to it.
> 
> I don't have any experience with spin locks either (at least none of
> the driver I wrote ever used one) but with over 4000 calls to this
> function throughout the kernel source tree, it shouldn't be
difficult
> to find an example you can follow.
> 

>> > (...)
>> > When CONFIG_I2C_DEBUG_ALGO isn't set, bit_dbg() is a no-op so it
>> > certainly can't affect you in any way.
>> > 
>> I don't know how the compiler do handle the bit_dbg() makro, but I
can
>> see the difference if the bit_dbg() call where included in the code
or
>> not,  also if  CONFIG_I2C_DEBUG_ALGO was not set.
> 
> This is highl
y unlikely, unless you modified the driver source code.
> bit_dbg is defined with:
> 
> #ifdef DEBUG
> #define bit_dbg(level, dev, format, args...) \
> 	do { \
> 		if (i2c_debug >= level) \
> 			dev_dbg(dev, format, ##args); \
> 	} while (0)
> #else
> #define bit_dbg(level, dev, format, args...) \
> 	do {} while (0)
> #endif /* DEBUG */
> 
> And DEBUG is only set if CONFIG_I2C_DEBUG_ALGO=y. So bit_dbg() is a
> no-op when CONFIG_I2C_DEBUG_ALGO isn't set.
> 
> As a matter of fact, I just tried removing all calls to bit_dbg()
and
> i2c-algo-bit.o is unchanged, as I expected. So either you messed up
> your testing, or your compiler is seriously broken.
> 
I'll do further tests to see what's going wrong.

>> > Question is whether the SCL line is stretched by the master or by
>> > the slave. Both are allowed to do it to a certain point.
>>
>> in the board settings I configure the SCL signal as output only to
>> avoid that SCL streching can be done by the SMBus slaves.
> 
> Oh my! You shot yourself in the foot!
> 
> How do you expect _slaves_ to change their behavior just because you
> said your I2C master to not pay attention to clock stretching? If
> slaves want to stretch the clock line, they will. The MLX90614
> datasheet isn't mentioning clock stretching, but that doesn't mean
the
> device is not doing exactly that.
> 
> You really want a bidirectional SCL on the master side, otherwise
> reliability cannot be guaranteed. In fact, i2c-algo-bit with no SCL
read
> callback is not I2C-compliant. It's just a hack because sometimes we
> have no other way, but in real systems you really don't want to do
> that. Maybe I should make i2c-algo-bit complain when SCL read
callback
> is missing, to make it more obvious.
> 
> So please fix this, set a proper callback for SCL read. This alone
> might fix your problem.
> 
I remove the SCL Output only setting and as open drain line.

Then I take some screenshots with the I2C analyzer. using series
resistors on the SMBus I could visualize which of the devices connected
to the SMBus throws the SCL or the SDA. The higher logic-Low-level is
thrown by the SMBus slave and the lower from the SMBus-master. I drop
these screenshots on my Dropbox:
http://www.dropbox.com/gallery/16457261/1/I2C_2_MLX90614?h=8e2a46

Where are the these callback functions located? In i2c-algo-bits,
i2c-core, or i2c-gpio?

>> > Does stretching happen on SCL high, or SCL low, or both?
>>
>> The streching occures on both levels at un predictable times.
> 
> This would be on the master side then. Slaves can stretch the clock
> line by holding it down, but they can't prevent it from going down
if
> the master pulls it low, so they can't stretch the high part of the
> clock cycle.
> 

>> > If the stretching is done by the master, then you may search for
>> > interrupt sources on your system. Maybe you have a misbehaving
>> > driver or device on your system which causes repeated and long
>> > interruptions. Making these interruptions shorter (e.g. by moving
>> > the real work to a workqueue) would then help.
>>
>> I have no ideea how to find a missbehaving driver, if any?
> 
> This isn't trivial. You can try unloading each driver sequentially
and
> see if things get better when one driver is missing. You can also
check
> in /proc/interrupts if any value is increasing particularly fast, or
if
> you can find a correlation between SCL problems and a particular
> interrupt.
> 
> Some kernel debug options might be helpful here, such as
> CONFIG_DETECT_SOFTLOCKUP and CONFIG_LATENCYTOP, and maybe others.
I'm
> not too familiar with this.

When printk output  is called and as well in the debug output
functions, the SCL signal is strechted until the output function has
finished to send data to the console on ttyS0.

best regards
Matthias
matthias.zacharias-zGrmWZs6xXT+aS/vkh9bjw@public.gmane.org


--------------------
BMK electronic solutions GmbH
Werner-von-Siemens-Str. 6, Eingang 18 f
D-86159 Augsburg
Tel. +49 (0) 821 / 207 88 - 700
Fax +49 (0) 821 
/ 207 88 - 721
info-zGrmWZs6xXT+aS/vkh9bjw@public.gmane.org
Geschäftsführer: Dipl.-oec. Alois Knöferle
Sitz: Augsburg
HR-Nr.: B21197
---------------------

Diese E-mail kann vertrauliche Informationen enthalten. Falls Sie diese
E-Mail irrtümlich erhalten haben, informieren Sie bitte unverzüglich den
Absender und löschen Sie diese E-Mail von jedem Rechner, auch von den
Mailservern. Jede Verbreitung des Inhalts, auch die teilweise
Verbreitung, ist in diesem Fall untersagt. Außer bei Vorsatz oder grober
Fahrlässigkeit schliessen wir jegliche Haftung für Verluste oder Schäden
aus, die durch Viren befallene Software oder E-Mails verursacht werden.

This e-mail may contain confidential information. If you received this
e-mail in error, please contact the sender and delete this e-mail from
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misconduct we accept no liability for any loss or damage caused by
software or e-mail viruses.

Antw: Re: Need help to fix some issues with the linux driver "i2c-gpio"

[Matthias Zacharias]

Hi Jean,

>>> Jean Delvare <khali-PUYAD+kWke1g9hUCZPvPmw@public.gmane.org> schrieb am Samstag, 11. Dezember
2010 um
17:23 in Nachricht <20101211172336.35c434ef-R0o5gVi9kd7kN2dkZ6Wm7A@public.gmane.org>:
> Hi Matthias,
> 
> On Fri, 10 Dec 2010 16:21:43 +0100, Matthias Zacharias wrote:
>> Hi Jean,
>> 
>> >>> Jean Delvare <khali-PUYAD+kWke1g9hUCZPvPmw@public.gmane.org> schrieb am Montag, 6.
Dezember
>> 2010 um 11:25 in Nachricht
<20101206112557.3dc8ffe3-R0o5gVi9kd7kN2dkZ6Wm7A@public.gmane.org>
>> > I know that. My question was, did you try an alternative way? For
>> > example you could use the i2cget command line tool (part of
>> > i2c-tools) for user-space access. It would be interesting to see
if
>> > it makes a difference.
>> 
>> I don't get the i2c-tools compiled for my armv5l platform. So can't
try
>> to work with these tools. Do you know how to get the i2c-tools
working
>> on an ARM9 microcontroller.
> 
> How do you expect me to help you here? You did not provide any hint
at
> what is failing. I don't have any ARM platform at hand.
> 
>> I think it's a problem of setting the right configuration.
> 
> "Setting the right configuration" is awfully vague. What do you
mean?
> If you have trouble building i2c-tools, please start a new
discussion
> thread for that with all the details and I'll look into it.
> 
I'll start a new thread for compiling the i2c-tools on ARM platforms

>> > You really want a bidirectional SCL on the master side, otherwise
>> > reliability cannot be guaranteed. In fact, i2c-algo-bit with no
SCL
>> > read callback is not I2C-compliant. It's just a hack because
>> > sometimes we have no other way, but in real systems you really
don't
>> > want to do that. Maybe I should make i2c-algo-bit complain when
SCL
>> > read callback is missing, to make it more obvious.
>> > 
>> > So please fix this, set a proper callback for SCL read. This
alone
>> > might fix your problem.
>>
>> I remove the SCL Output only setting and as open drain line.
> 
> Good.
> 
>> Then I take some screenshots with the I2C analyzer. using series
>> resistors on the SMBus I could visualize which of the devices
connected
>> to the SMBus throws the SCL or the SDA. The higher logic-Low-level
is
>> thrown by the SMBus slave and the lower from the SMBus-master.
> 
> My electronics knowledge is fairly limited, I didn't even know this
was
> possible. So I(ll trust you ;)
> 
>> I drop these screenshots on my Dropbox:
>> http://www.dropbox.com/gallery/16457261/1/I2C_2_MLX90614?h=8e2a46 
> 
> Interesting. I see that you included both traces from the MLX90614
and
> traces from the EEPROM, and both exhibit the problem. This, and the
fact
> that the clock line can be stuck both high and low, clearly points
at
> the master.
> 
> If EEPROM access still works fine, this is probably because the
EEPROM
> is more tolerant to clock stalls.
> 
> If I read the screenshots correctly, the problem only happens when
SCL
> stalls high, not low, and only for the MLX90614, right?
> 
> This would match the timeouts documented in the MLX90614 datasheet:
> only 50 µs when SCL is high. This matches the SMBus specification,
BTW,
> while I2C doesn't have any such timeout.
> 
>> Where are the these callback functions located? In i2c-algo-bits,
>> i2c-core, or i2c-gpio?
> 
> Your code (user-space or kernel driver) calls into i2c-core, which
> calls i2c-algo-bit. The functions in i2c-algo-bit ultimately call
into
> i2c-gpio, which forwards the requests directly to the low-level GPIO
> code.
> 
> Such timing problems can't be caused by i2c-core, which is way too
high
> level. i2c-gpio is only a middle man between the software
bit-banging
> logic (i2c-algo-bit) and the physical level (gpio), so I doubt
anything
> can be wrong there. If something is actually wrong in i2c-gpio, it
> would be in the initial setup (i2c_gpio_probe), not the callbacks. I
> definitely hope that you already double-checked that the setup data
for
> i2c-gpio is correct (including pdata->sda_is_open_drain and
> pdata->scl_is_op
en_drain).
> 
> So the suspects are i2c-algo-bit and the low-level GPIO code.
> 
> For i2c-algo-bit, as I already said, the known issue is that the bus
is
> software-driven, and the code driving the bus can be preempted by an
> interrupt. I already suggested that you should check what interrupts
> are happening on your system during the I2C transfers.
> 
> The low-level GPIO code is suspect too. i2c-algo-bit assumes that
> setting SDA or SCL is very fast, and reading them too. If any of the
> callbacks takes a significant amount of time, then the timing
> assumptions made by i2c-algo-bit will tear apart. Unfortunately I am
not
> familiar with GPIOs, and I have no idea how to accurately measure
how
> long the GPIO callbacks last.
> 
> Actually, what I see on your analyzer screenshots could be caused by
> either of these two problems.
> 
>> (...)
>> When printk output  is called and as well in the debug output
>> functions, the SCL signal is strechted until the output function
has
>> finished to send data to the console on ttyS0.
> 
> This is correct. But in your case, the problem happens even without
> printk being ever called, right? So that's not the problem.
> 
> Here is a patch I came up with, which I would like you to try. It
blocks
> interrupts while SCL is high. Please use your I2C analyzer again
with
> this patch applied. What I expect is that you will still see
stretched
> clocks, but only when SCL is low. The timeout of the MLX90614 is
much
> higher when SCL is low, so I hope that the clock stretching will be
> properly handled this time and the MLX90614 will work fine.
> 
> ---
>  drivers/i2c/algos/i2c-algo-bit.c |   17 +++++++++++++++++
>  include/linux/i2c-algo-bit.h     |    3 +++
>  2 files changed, 20 insertions(+)
> 
> ---
linux-2.6.27.orig/drivers/i2c/algos/i2c-algo-bit.c	2010-12-11
16:09:18.000000000 
> +0100
> +++ linux-2.6.27/drivers/i2c/algos/i2c-algo-bit.c	2010-12-11
16:52:30.000000000 
> +0100
> @@ -30,6 +30,7 @@
>  #include <linux/sched.h>
>  #include <linux/i2c.h>
>  #include <linux/i2c-algo-bit.h>
> +#include <linux/spinlock.h>
>  
>  
>  /* ----- global defines
----------------------------------------------- */
> @@ -164,15 +165,18 @@ static int i2c_outb(struct i2c_adapter *
>  	int sb;
>  	int ack;
>  	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
> +	unsigned long flags;
>  
>  	/* assert: scl is low */
>  	for (i = 7; i >= 0; i--) {
>  		sb = (c >> i) & 1;
>  		setsda(adap, sb);
>  		udelay((adap->udelay + 1) / 2);
> +		spin_lock_irqsave(&adap->lockscl, flags);
>  		if (sclhi(adap) < 0) { /* timed out */
>  			bit_dbg(1, &i2c_adap->dev, "i2c_outb: 0x%02x, "
>  				"timeout at bit #%d\n", (int)c, i);
> +			spin_unlock_irqrestore(&adap->lockscl, flags);
>  			return -ETIMEDOUT;
>  		}
>  		/* FIXME do arbitration here:
> @@ -182,11 +186,14 @@ static int i2c_outb(struct i2c_adapter *
>  		 * the whole (combined) message and *NOT* issue STOP.
>  		 */
>  		scllo(adap);
> +		spin_unlock_irqrestore(&adap->lockscl, flags);
>  	}
>  	sdahi(adap);
> +	spin_lock_irqsave(&adap->lockscl, flags);
>  	if (sclhi(adap) < 0) { /* timeout */
>  		bit_dbg(1, &i2c_adap->dev, "i2c_outb: 0x%02x, "
>  			"timeout at ack\n", (int)c);
> +		spin_unlock_irqrestore(&adap->lockscl, flags);
>  		return -ETIMEDOUT;
>  	}
>  
> @@ -198,6 +205,7 @@ static int i2c_outb(struct i2c_adapter *
>  		ack ? "A" : "NA");
>  
>  	scllo(adap);
> +	spin_unlock_irqrestore(&adap->lockscl, flags);
>  	return ack;
>  	/* assert: scl is low (sda undef) */
>  }
> @@ -210,19 +218,23 @@ static int i2c_inb(struct i2c_adapter *i
>  	int i;
>  	unsigned char indata = 0;
>  	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
> +	unsigned long flags;
>  
>  	/* assert: scl is low */
>  	sdahi(adap);
>  	for (i = 0; i < 8; i++) {
> +		spin_lock_irqsave(&adap->lockscl, flags);
>  		if (sclhi(adap) < 0) { /* timeout */
>  			bit_dbg(1, &i2c_adap->dev, "i2c_inb: timeout at
bit "
>  				"#%d\n", 7 - i);
> +			spin_unlock_irqr
estore(&adap->lockscl, flags);
>  			return -ETIMEDOUT;
>  		}
>  		indata *= 2;
>  		if (getsda(adap))
>  			indata |= 0x01;
>  		setscl(adap, 0);
> +		spin_unlock_irqrestore(&adap->lockscl, flags);
>  		udelay(i == 7 ? adap->udelay / 2 : adap->udelay);
>  	}
>  	/* assert: scl is low */
> @@ -385,16 +397,20 @@ static int sendbytes(struct i2c_adapter 
>  static int acknak(struct i2c_adapter *i2c_adap, int is_ack)
>  {
>  	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
> +	unsigned long flags;
>  
>  	/* assert: sda is high */
>  	if (is_ack)		/* send ack */
>  		setsda(adap, 0);
>  	udelay((adap->udelay + 1) / 2);
> +	spin_lock_irqsave(&adap->lockscl, flags);
>  	if (sclhi(adap) < 0) {	/* timeout */
>  		dev_err(&i2c_adap->dev, "readbytes: ack/nak
timeout\n");
> +		spin_unlock_irqrestore(&adap->lockscl, flags);
>  		return -ETIMEDOUT;
>  	}
>  	scllo(adap);
> +	spin_unlock_irqrestore(&adap->lockscl, flags);
>  	return 0;
>  }
>  
> @@ -603,6 +619,7 @@ static int i2c_bit_prepare_bus(struct i2
>  	}
>  
>  	/* register new adapter to i2c module... */
> +	spin_lock_init(&bit_adap->lockscl);
>  	adap->algo = &i2c_bit_algo;
>  
>  	adap->timeout = 100;	/* default values, should	*/
> --- linux-2.6.27.orig/include/linux/i2c-algo-bit.h	2008-04-17
04:49:44.000000000 
> +0200
> +++ linux-2.6.27/include/linux/i2c-algo-bit.h	2010-12-11
16:53:22.000000000 +0100
> @@ -24,6 +24,8 @@
>  #ifndef _LINUX_I2C_ALGO_BIT_H
>  #define _LINUX_I2C_ALGO_BIT_H
>  
> +#include <linux/spinlock.h>
> +
>  /* --- Defines for bit-adapters
---------------------------------------	*/
>  /*
>   * This struct contains the hw-dependent functions of bit-style
adapters to
> @@ -36,6 +38,7 @@ struct i2c_algo_bit_data {
>  	void (*setscl) (void *data, int state);
>  	int  (*getsda) (void *data);
>  	int  (*getscl) (void *data);
> +	spinlock_t lockscl;
>  
>  	/* local settings */
>  	int udelay;		/* half clock cycle time in us,

Thanks for your patch. It is working very well. 
But one problem is left:
    see "101214_1058_MLX_I2C_patched_0001.bmp" in my dropbox
(http://www.dropbox.com/gallery/16457261/1/I2C_2_MLX90614?h=8e2a46)

If between the read command (0x5a.0x6) and the answer (0x5a <3x
data_bytes) the timeout condition:  SCL = High for 43µs match, the
MLX90614 go thru reset and returns an invalid value (0xFFFF).

Where can I place the call for "spin_lock_irqsave" and
"spin_unlock_irqrestore" to block this timeout situation.

best regards
Matthias Zacharias


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Re: Need help to fix some issues with the linux driver "i2c-gpio"

[Jean Delvare]

Hi Matthias,

On Tue, 14 Dec 2010 15:14:13 +0100, Matthias Zacharias wrote:
> Thanks for your patch. It is working very well. 
> But one problem is left:
>     see "101214_1058_MLX_I2C_patched_0001.bmp" in my dropbox
> (http://www.dropbox.com/gallery/16457261/1/I2C_2_MLX90614?h=8e2a46)
> 
> If between the read command (0x5a.0x6) and the answer (0x5a <3x
> data_bytes) the timeout condition:  SCL = High for 43µs match, the
> MLX90614 go thru reset and returns an invalid value (0xFFFF).
> 
> Where can I place the call for "spin_lock_irqsave" and
> "spin_unlock_irqrestore" to block this timeout situation.

Ah, I forgot the repeated start condition. The following updated patch
fixes this. I have also changed the code to no longer call scllo() when
the spinlock is held. That way we can release the spinlock (and thus
enable interrupts again) faster, which lowers the system latency.

So please give a try to this new patch, and report.

* * * * *

Candidate fix for SCL getting stretched when high resulting in
slave timeouts.

Signed-off-by: Jean Delvare <khali-PUYAD+kWke1g9hUCZPvPmw@public.gmane.org>
---
 drivers/i2c/algos/i2c-algo-bit.c |   33 +++++++++++++++++++++++++++++----
 include/linux/i2c-algo-bit.h     |    3 +++
 2 files changed, 32 insertions(+), 4 deletions(-)

--- linux-2.6.27.orig/drivers/i2c/algos/i2c-algo-bit.c	2010-12-14 17:34:48.000000000 +0100
+++ linux-2.6.27/drivers/i2c/algos/i2c-algo-bit.c	2010-12-14 17:34:50.000000000 +0100
@@ -30,6 +30,7 @@
 #include <linux/sched.h>
 #include <linux/i2c.h>
 #include <linux/i2c-algo-bit.h>
+#include <linux/spinlock.h>
 
 
 /* ----- global defines ----------------------------------------------- */
@@ -131,12 +132,17 @@ static void i2c_start(struct i2c_algo_bi
 
 static void i2c_repstart(struct i2c_algo_bit_data *adap)
 {
+	unsigned long flags;
+
 	/* assert: scl is low */
 	sdahi(adap);
+	spin_lock_irqsave(&adap->lockscl, flags);
 	sclhi(adap);
 	setsda(adap, 0);
 	udelay(adap->udelay);
-	scllo(adap);
+	setscl(adap, 0);
+	spin_unlock_irqrestore(&adap->lockscl, flags);
+	udelay(adap->udelay / 2);
 }
 
 
@@ -164,15 +170,18 @@ static int i2c_outb(struct i2c_adapter *
 	int sb;
 	int ack;
 	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
+	unsigned long flags;
 
 	/* assert: scl is low */
 	for (i = 7; i >= 0; i--) {
 		sb = (c >> i) & 1;
 		setsda(adap, sb);
 		udelay((adap->udelay + 1) / 2);
+		spin_lock_irqsave(&adap->lockscl, flags);
 		if (sclhi(adap) < 0) { /* timed out */
 			bit_dbg(1, &i2c_adap->dev, "i2c_outb: 0x%02x, "
 				"timeout at bit #%d\n", (int)c, i);
+			spin_unlock_irqrestore(&adap->lockscl, flags);
 			return -ETIMEDOUT;
 		}
 		/* FIXME do arbitration here:
@@ -181,12 +190,16 @@ static int i2c_outb(struct i2c_adapter *
 		 * Report a unique code, so higher level code can retry
 		 * the whole (combined) message and *NOT* issue STOP.
 		 */
-		scllo(adap);
+		setscl(adap, 0);
+		spin_unlock_irqrestore(&adap->lockscl, flags);
+		udelay(adap->udelay / 2);
 	}
 	sdahi(adap);
+	spin_lock_irqsave(&adap->lockscl, flags);
 	if (sclhi(adap) < 0) { /* timeout */
 		bit_dbg(1, &i2c_adap->dev, "i2c_outb: 0x%02x, "
 			"timeout at ack\n", (int)c);
+		spin_unlock_irqrestore(&adap->lockscl, flags);
 		return -ETIMEDOUT;
 	}
 
@@ -197,7 +210,9 @@ static int i2c_outb(struct i2c_adapter *
 	bit_dbg(2, &i2c_adap->dev, "i2c_outb: 0x%02x %s\n", (int)c,
 		ack ? "A" : "NA");
 
-	scllo(adap);
+	setscl(adap, 0);
+	spin_unlock_irqrestore(&adap->lockscl, flags);
+	udelay(adap->udelay / 2);
 	return ack;
 	/* assert: scl is low (sda undef) */
 }
@@ -210,19 +225,23 @@ static int i2c_inb(struct i2c_adapter *i
 	int i;
 	unsigned char indata = 0;
 	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
+	unsigned long flags;
 
 	/* assert: scl is low */
 	sdahi(adap);
 	for (i = 0; i < 8; i++) {
+		spin_lock_irqsave(&adap->lockscl, flags);
 		if (sclhi(adap) < 0) { /* timeout */
 			bit_dbg(1, &i2c_adap->dev, "i2c_inb: timeout at bit "
 				"#%d\n", 7 - i);
+			spin_unlock_irqrestore(&adap->lockscl, flags);
 			return -ETIMEDOUT;
 		}
 		indata *= 2;
 		if (getsda(adap))
 			indata |= 0x01;
 		setscl(adap, 0);
+		spin_unlock_irqrestore(&adap->lockscl, flags);
 		udelay(i == 7 ? adap->udelay / 2 : adap->udelay);
 	}
 	/* assert: scl is low */
@@ -385,16 +404,21 @@ static int sendbytes(struct i2c_adapter 
 static int acknak(struct i2c_adapter *i2c_adap, int is_ack)
 {
 	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
+	unsigned long flags;
 
 	/* assert: sda is high */
 	if (is_ack)		/* send ack */
 		setsda(adap, 0);
 	udelay((adap->udelay + 1) / 2);
+	spin_lock_irqsave(&adap->lockscl, flags);
 	if (sclhi(adap) < 0) {	/* timeout */
 		dev_err(&i2c_adap->dev, "readbytes: ack/nak timeout\n");
+		spin_unlock_irqrestore(&adap->lockscl, flags);
 		return -ETIMEDOUT;
 	}
-	scllo(adap);
+	setscl(adap, 0);
+	spin_unlock_irqrestore(&adap->lockscl, flags);
+	udelay(adap->udelay / 2);
 	return 0;
 }
 
@@ -603,6 +627,7 @@ static int i2c_bit_prepare_bus(struct i2
 	}
 
 	/* register new adapter to i2c module... */
+	spin_lock_init(&bit_adap->lockscl);
 	adap->algo = &i2c_bit_algo;
 
 	adap->timeout = 100;	/* default values, should	*/
--- linux-2.6.27.orig/include/linux/i2c-algo-bit.h	2010-12-14 17:34:49.000000000 +0100
+++ linux-2.6.27/include/linux/i2c-algo-bit.h	2010-12-14 17:35:30.000000000 +0100
@@ -24,6 +24,8 @@
 #ifndef _LINUX_I2C_ALGO_BIT_H
 #define _LINUX_I2C_ALGO_BIT_H
 
+#include <linux/spinlock.h>
+
 /* --- Defines for bit-adapters ---------------------------------------	*/
 /*
  * This struct contains the hw-dependent functions of bit-style adapters to
@@ -36,6 +38,7 @@ struct i2c_algo_bit_data {
 	void (*setscl) (void *data, int state);
 	int  (*getsda) (void *data);
 	int  (*getscl) (void *data);
+	spinlock_t lockscl;
 
 	/* local settings */
 	int udelay;		/* half clock cycle time in us,


-- 
Jean Delvare

Antw: Re: Need help to fix some issues with the linux driver "i2c-gpio"

[Matthias Zacharias]

Hi Jean,

Thank you for the new patch.
I tried it and it works fine for our system with i2c_debug < 2. For
i2c_debug >=2 the debug outputs leads to timeout condition when address
should be acknowledged.

I'll try to publish the "mlx90614" driver after doing some
optimizations. Are you interested to review this driver before, because
it is the first driver we try to publish?

Do plan to include your patch on the "i2c-algo-bit" into the lastest
kernel?
I had applied the patch and done my tests on the 2.6.25.4 kernel, with
a bunch of other patches needed for my system. 

Thanks a lot for your fast and good support for fixing this issue we
had.

Best regards
Matthias Zacharias
matthias.zacharias-zGrmWZs6xXT+aS/vkh9bjw@public.gmane.org


>>> Jean Delvare <khali-PUYAD+kWke1g9hUCZPvPmw@public.gmane.org> schrieb am Dienstag, 14. Dezember
2010 um
17:58 in Nachricht <20101214175828.0a62ce3f-R0o5gVi9kd7kN2dkZ6Wm7A@public.gmane.org>:
> Hi Matthias,
> 
> On Tue, 14 Dec 2010 15:14:13 +0100, Matthias Zacharias wrote:
>> Thanks for your patch. It is working very well. 
>> But one problem is left:
>>     see "101214_1058_MLX_I2C_patched_0001.bmp" in my dropbox
>> (http://www.dropbox.com/gallery/16457261/1/I2C_2_MLX90614?h=8e2a46)
>> 
>> If between the read command (0x5a.0x6) and the answer (0x5a <3x
>> data_bytes) the timeout condition:  SCL = High for 43µs match, the
>> MLX90614 go thru reset and returns an invalid value (0xFFFF).
>> 
>> Where can I place the call for "spin_lock_irqsave" and
>> "spin_unlock_irqrestore" to block this timeout situation.
> 
> Ah, I forgot the repeated start condition. The following updated
patch
> fixes this. I have also changed the code to no longer call scllo()
when
> the spinlock is held. That way we can release the spinlock (and thus
> enable interrupts again) faster, which lowers the system latency.
> 
> So please give a try to this new patch, and report.
> 
> * * * * *
> 
> Candidate fix for SCL getting stretched when high resulting in
> slave timeouts.
> 
> Signed-off-by: Jean Delvare <khali-PUYAD+kWke1g9hUCZPvPmw@public.gmane.org>
> ---
>  drivers/i2c/algos/i2c-algo-bit.c |   33
+++++++++++++++++++++++++++++----
>  include/linux/i2c-algo-bit.h     |    3 +++
>  2 files changed, 32 insertions(+), 4 deletions(-)
> 
> ---
linux-2.6.27.orig/drivers/i2c/algos/i2c-algo-bit.c	2010-12-14
17:34:48.000000000 
> +0100
> +++ linux-2.6.27/drivers/i2c/algos/i2c-algo-bit.c	2010-12-14
17:34:50.000000000 
> +0100
> @@ -30,6 +30,7 @@
>  #include <linux/sched.h>
>  #include <linux/i2c.h>
>  #include <linux/i2c-algo-bit.h>
> +#include <linux/spinlock.h>
>  
>  
>  /* ----- global defines
----------------------------------------------- */
> @@ -131,12 +132,17 @@ static void i2c_start(struct i2c_algo_bi
>  
>  static void i2c_repstart(struct i2c_algo_bit_data *adap)
>  {
> +	unsigned long flags;
> +
>  	/* assert: scl is low */
>  	sdahi(adap);
> +	spin_lock_irqsave(&adap->lockscl, flags);
>  	sclhi(adap);
>  	setsda(adap, 0);
>  	udelay(adap->udelay);
> -	scllo(adap);
> +	setscl(adap, 0);
> +	spin_unlock_irqrestore(&adap->lockscl, flags);
> +	udelay(adap->udelay / 2);
>  }
>  
>  
> @@ -164,15 +170,18 @@ static int i2c_outb(struct i2c_adapter *
>  	int sb;
>  	int ack;
>  	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
> +	unsigned long flags;
>  
>  	/* assert: scl is low */
>  	for (i = 7; i >= 0; i--) {
>  		sb = (c >> i) & 1;
>  		setsda(adap, sb);
>  		udelay((adap->udelay + 1) / 2);
> +		spin_lock_irqsave(&adap->lockscl, flags);
>  		if (sclhi(adap) < 0) { /* timed out */
>  			bit_dbg(1, &i2c_adap->dev, "i2c_outb: 0x%02x, "
>  				"timeout at bit #%d\n", (int)c, i);
> +			spin_unlock_irqrestore(&adap->lockscl, flags);
>  			return -ETIMEDOUT;
>  		}
>  		/* FIXME do arbitration here:
> @@ -181,12 +190,16 @@ static int i2c_outb(struct i2c_adapter *
>  		 * Report a unique code, so higher level code can retry
>  		 * the whole (combined) message and *NOT* issue STOP.
>  		 */
> -		scllo(adap);
> +		setscl(adap, 0);
> +		
spin_unlock_irqrestore(&adap->lockscl, flags);
> +		udelay(adap->udelay / 2);
>  	}
>  	sdahi(adap);
> +	spin_lock_irqsave(&adap->lockscl, flags);
>  	if (sclhi(adap) < 0) { /* timeout */
>  		bit_dbg(1, &i2c_adap->dev, "i2c_outb: 0x%02x, "
>  			"timeout at ack\n", (int)c);
> +		spin_unlock_irqrestore(&adap->lockscl, flags);
>  		return -ETIMEDOUT;
>  	}
>  
> @@ -197,7 +210,9 @@ static int i2c_outb(struct i2c_adapter *
>  	bit_dbg(2, &i2c_adap->dev, "i2c_outb: 0x%02x %s\n", (int)c,
>  		ack ? "A" : "NA");
>  
> -	scllo(adap);
> +	setscl(adap, 0);
> +	spin_unlock_irqrestore(&adap->lockscl, flags);
> +	udelay(adap->udelay / 2);
>  	return ack;
>  	/* assert: scl is low (sda undef) */
>  }
> @@ -210,19 +225,23 @@ static int i2c_inb(struct i2c_adapter *i
>  	int i;
>  	unsigned char indata = 0;
>  	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
> +	unsigned long flags;
>  
>  	/* assert: scl is low */
>  	sdahi(adap);
>  	for (i = 0; i < 8; i++) {
> +		spin_lock_irqsave(&adap->lockscl, flags);
>  		if (sclhi(adap) < 0) { /* timeout */
>  			bit_dbg(1, &i2c_adap->dev, "i2c_inb: timeout at
bit "
>  				"#%d\n", 7 - i);
> +			spin_unlock_irqrestore(&adap->lockscl, flags);
>  			return -ETIMEDOUT;
>  		}
>  		indata *= 2;
>  		if (getsda(adap))
>  			indata |= 0x01;
>  		setscl(adap, 0);
> +		spin_unlock_irqrestore(&adap->lockscl, flags);
>  		udelay(i == 7 ? adap->udelay / 2 : adap->udelay);
>  	}
>  	/* assert: scl is low */
> @@ -385,16 +404,21 @@ static int sendbytes(struct i2c_adapter 
>  static int acknak(struct i2c_adapter *i2c_adap, int is_ack)
>  {
>  	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
> +	unsigned long flags;
>  
>  	/* assert: sda is high */
>  	if (is_ack)		/* send ack */
>  		setsda(adap, 0);
>  	udelay((adap->udelay + 1) / 2);
> +	spin_lock_irqsave(&adap->lockscl, flags);
>  	if (sclhi(adap) < 0) {	/* timeout */
>  		dev_err(&i2c_adap->dev, "readbytes: ack/nak
timeout\n");
> +		spin_unlock_irqrestore(&adap->lockscl, flags);
>  		return -ETIMEDOUT;
>  	}
> -	scllo(adap);
> +	setscl(adap, 0);
> +	spin_unlock_irqrestore(&adap->lockscl, flags);
> +	udelay(adap->udelay / 2);
>  	return 0;
>  }
>  
> @@ -603,6 +627,7 @@ static int i2c_bit_prepare_bus(struct i2
>  	}
>  
>  	/* register new adapter to i2c module... */
> +	spin_lock_init(&bit_adap->lockscl);
>  	adap->algo = &i2c_bit_algo;
>  
>  	adap->timeout = 100;	/* default values, should	*/
> --- linux-2.6.27.orig/include/linux/i2c-algo-bit.h	2010-12-14
17:34:49.000000000 
> +0100
> +++ linux-2.6.27/include/linux/i2c-algo-bit.h	2010-12-14
17:35:30.000000000 +0100
> @@ -24,6 +24,8 @@
>  #ifndef _LINUX_I2C_ALGO_BIT_H
>  #define _LINUX_I2C_ALGO_BIT_H
>  
> +#include <linux/spinlock.h>
> +
>  /* --- Defines for bit-adapters
---------------------------------------	*/
>  /*
>   * This struct contains the hw-dependent functions of bit-style
adapters to
> @@ -36,6 +38,7 @@ struct i2c_algo_bit_data {
>  	void (*setscl) (void *data, int state);
>  	int  (*getsda) (void *data);
>  	int  (*getscl) (void *data);
> +	spinlock_t lockscl;
>  
>  	/* local settings */
>  	int udelay;		/* half clock cycle time in us,

--------------------
BMK electronic solutions GmbH
Werner-von-Siemens-Str. 6, Eingang 18 f
D-86159 Augsburg
Tel. +49 (0) 821 / 207 88 - 700
Fax +49 (0) 821 / 207 88 - 721
info-zGrmWZs6xXT+aS/vkh9bjw@public.gmane.org
Geschäftsführer: Dipl.-oec. Alois Knöferle
Sitz: Augsburg
HR-Nr.: B21197
---------------------

Diese E-mail kann vertrauliche Informationen enthalten. Falls Sie diese
E-Mail irrtümlich erhalten haben, informieren Sie bitte unverzüglich den
Absender und löschen Sie diese E-Mail von jedem Rechner, auch von den
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This e-mail may contain confidential
 information. If you received this
e-mail in error, please contact the sender and delete this e-mail from
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misconduct we accept no liability for any loss or damage caused by
software or e-mail viruses.

Re: Need help to fix some issues with the linux driver "i2c-gpio"

[Jean Delvare]

[-- Attachment #1: Type: text/plain, Size: 1710 bytes --]

Hallo Matthias,

On Wed, 15 Dec 2010 13:46:26 +0100, Matthias Zacharias wrote:
> Thank you for the new patch.
> I tried it and it works fine for our system with i2c_debug < 2.

Great, thanks for the feedback.

> For i2c_debug >=2 the debug outputs leads to timeout condition when
> address should be acknowledged.

Hmm, calling printk() with the spinlock held wasn't the smartest thing
to do, I guess. Updated patch attached, I've made sure to always
release the spinlock before calling bit_dbg(), hopefully it should fix
your last issue.

> I'll try to publish the "mlx90614" driver after doing some
> optimizations. Are you interested to review this driver before, because
> it is the first driver we try to publish?

Just publish it as is, and I'll review it publicly. It will certainly
take a number of round trips to get it right, if this is your first
contribution, but that's OK.

FYI, I have asked Melexis for an MLX90614 evaluation board, they have
sent something to me, so as soon as I receive it I should be able to
test your driver.

> Do plan to include your patch on the "i2c-algo-bit" into the lastest
> kernel?

Yes. Please test the new version of the patch, and if it works OK for
you, I'll schedule it for merge in kernel 2.6.38. For 2.6.37 it's too
late, the patch is quite intrusive and i2c-algo-bit is used by many
many drivers including very popular ones, so I can't merge it that late
in the release cycle.

> I had applied the patch and done my tests on the 2.6.25.4 kernel, with
> a bunch of other patches needed for my system. 
> 
> Thanks a lot for your fast and good support for fixing this issue we
> had.

You're welcome.

-- 
Jean Delvare
http://khali.linux-fr.org/wishlist.html

[-- Attachment #2: i2c-algo-bit-protect-scl-high.patch --]
[-- Type: text/x-patch, Size: 5027 bytes --]

Candidate fix for SCL getting stretched when high resulting in
slave timeouts.

Signed-off-by: Jean Delvare <khali-PUYAD+kWke1g9hUCZPvPmw@public.gmane.org>
---
 drivers/i2c/algos/i2c-algo-bit.c |   34 ++++++++++++++++++++++++++++++----
 include/linux/i2c-algo-bit.h     |    3 +++
 2 files changed, 33 insertions(+), 4 deletions(-)

--- linux-2.6.27.orig/drivers/i2c/algos/i2c-algo-bit.c	2010-12-15 15:25:12.000000000 +0100
+++ linux-2.6.27/drivers/i2c/algos/i2c-algo-bit.c	2010-12-15 15:25:26.000000000 +0100
@@ -30,6 +30,7 @@
 #include <linux/sched.h>
 #include <linux/i2c.h>
 #include <linux/i2c-algo-bit.h>
+#include <linux/spinlock.h>
 
 
 /* ----- global defines ----------------------------------------------- */
@@ -131,12 +132,17 @@ static void i2c_start(struct i2c_algo_bi
 
 static void i2c_repstart(struct i2c_algo_bit_data *adap)
 {
+	unsigned long flags;
+
 	/* assert: scl is low */
 	sdahi(adap);
+	spin_lock_irqsave(&adap->lockscl, flags);
 	sclhi(adap);
 	setsda(adap, 0);
 	udelay(adap->udelay);
-	scllo(adap);
+	setscl(adap, 0);
+	spin_unlock_irqrestore(&adap->lockscl, flags);
+	udelay(adap->udelay / 2);
 }
 
 
@@ -164,13 +170,16 @@ static int i2c_outb(struct i2c_adapter *
 	int sb;
 	int ack;
 	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
+	unsigned long flags;
 
 	/* assert: scl is low */
 	for (i = 7; i >= 0; i--) {
 		sb = (c >> i) & 1;
 		setsda(adap, sb);
 		udelay((adap->udelay + 1) / 2);
+		spin_lock_irqsave(&adap->lockscl, flags);
 		if (sclhi(adap) < 0) { /* timed out */
+			spin_unlock_irqrestore(&adap->lockscl, flags);
 			bit_dbg(1, &i2c_adap->dev, "i2c_outb: 0x%02x, "
 				"timeout at bit #%d\n", (int)c, i);
 			return -ETIMEDOUT;
@@ -181,10 +190,14 @@ static int i2c_outb(struct i2c_adapter *
 		 * Report a unique code, so higher level code can retry
 		 * the whole (combined) message and *NOT* issue STOP.
 		 */
-		scllo(adap);
+		setscl(adap, 0);
+		spin_unlock_irqrestore(&adap->lockscl, flags);
+		udelay(adap->udelay / 2);
 	}
 	sdahi(adap);
+	spin_lock_irqsave(&adap->lockscl, flags);
 	if (sclhi(adap) < 0) { /* timeout */
+		spin_unlock_irqrestore(&adap->lockscl, flags);
 		bit_dbg(1, &i2c_adap->dev, "i2c_outb: 0x%02x, "
 			"timeout at ack\n", (int)c);
 		return -ETIMEDOUT;
@@ -194,10 +207,13 @@ static int i2c_outb(struct i2c_adapter *
 	 * NAK (usually to report problems with the data we wrote).
 	 */
 	ack = !getsda(adap);    /* ack: sda is pulled low -> success */
+	setscl(adap, 0);
+	spin_unlock_irqrestore(&adap->lockscl, flags);
+	udelay(adap->udelay / 2);
+
 	bit_dbg(2, &i2c_adap->dev, "i2c_outb: 0x%02x %s\n", (int)c,
 		ack ? "A" : "NA");
 
-	scllo(adap);
 	return ack;
 	/* assert: scl is low (sda undef) */
 }
@@ -210,11 +226,14 @@ static int i2c_inb(struct i2c_adapter *i
 	int i;
 	unsigned char indata = 0;
 	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
+	unsigned long flags;
 
 	/* assert: scl is low */
 	sdahi(adap);
 	for (i = 0; i < 8; i++) {
+		spin_lock_irqsave(&adap->lockscl, flags);
 		if (sclhi(adap) < 0) { /* timeout */
+			spin_unlock_irqrestore(&adap->lockscl, flags);
 			bit_dbg(1, &i2c_adap->dev, "i2c_inb: timeout at bit "
 				"#%d\n", 7 - i);
 			return -ETIMEDOUT;
@@ -223,6 +242,7 @@ static int i2c_inb(struct i2c_adapter *i
 		if (getsda(adap))
 			indata |= 0x01;
 		setscl(adap, 0);
+		spin_unlock_irqrestore(&adap->lockscl, flags);
 		udelay(i == 7 ? adap->udelay / 2 : adap->udelay);
 	}
 	/* assert: scl is low */
@@ -385,16 +405,21 @@ static int sendbytes(struct i2c_adapter 
 static int acknak(struct i2c_adapter *i2c_adap, int is_ack)
 {
 	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
+	unsigned long flags;
 
 	/* assert: sda is high */
 	if (is_ack)		/* send ack */
 		setsda(adap, 0);
 	udelay((adap->udelay + 1) / 2);
+	spin_lock_irqsave(&adap->lockscl, flags);
 	if (sclhi(adap) < 0) {	/* timeout */
+		spin_unlock_irqrestore(&adap->lockscl, flags);
 		dev_err(&i2c_adap->dev, "readbytes: ack/nak timeout\n");
 		return -ETIMEDOUT;
 	}
-	scllo(adap);
+	setscl(adap, 0);
+	spin_unlock_irqrestore(&adap->lockscl, flags);
+	udelay(adap->udelay / 2);
 	return 0;
 }
 
@@ -603,6 +628,7 @@ static int i2c_bit_prepare_bus(struct i2
 	}
 
 	/* register new adapter to i2c module... */
+	spin_lock_init(&bit_adap->lockscl);
 	adap->algo = &i2c_bit_algo;
 
 	adap->timeout = 100;	/* default values, should	*/
--- linux-2.6.27.orig/include/linux/i2c-algo-bit.h	2010-12-15 15:25:12.000000000 +0100
+++ linux-2.6.27/include/linux/i2c-algo-bit.h	2010-12-15 15:25:44.000000000 +0100
@@ -24,6 +24,8 @@
 #ifndef _LINUX_I2C_ALGO_BIT_H
 #define _LINUX_I2C_ALGO_BIT_H
 
+#include <linux/spinlock.h>
+
 /* --- Defines for bit-adapters ---------------------------------------	*/
 /*
  * This struct contains the hw-dependent functions of bit-style adapters to
@@ -36,6 +38,7 @@ struct i2c_algo_bit_data {
 	void (*setscl) (void *data, int state);
 	int  (*getsda) (void *data);
 	int  (*getscl) (void *data);
+	spinlock_t lockscl;
 
 	/* local settings */
 	int udelay;		/* half clock cycle time in us,

Antw: Re: Need help to fix some issues with the linux driver "i2c-gpio"

[Matthias Zacharias]

Hello Jean,

With the new patch the driver is working fine, also with i2c_debug =
3.

See the screenshot in my dropbox
(http://www.dropbox.com/gallery/16457261/1/I2C_2_MLX90614?h=8e2a46)

>>> Jean Delvare <khali-PUYAD+kWke1g9hUCZPvPmw@public.gmane.org> schrieb am Mittwoch, 15. Dezember
2010 um
15:42 in Nachricht <20101215154255.20d471a4-R0o5gVi9kd7kN2dkZ6Wm7A@public.gmane.org>:
> Hallo Matthias,
> 
> On Wed, 15 Dec 2010 13:46:26 +0100, Matthias Zacharias wrote:
>> Thank you for the new patch.
>> I tried it and it works fine for our system with i2c_debug < 2.
> 
> Great, thanks for the feedback.
> 
>> For i2c_debug >=2 the debug outputs leads to timeout condition when
>> address should be acknowledged.
> 
> Hmm, calling printk() with the spinlock held wasn't the smartest
thing
> to do, I guess. Updated patch attached, I've made sure to always
> release the spinlock before calling bit_dbg(), hopefully it should
fix
> your last issue.
> 
>> I'll try to publish the "mlx90614" driver after doing some
>> optimizations. Are you interested to review this driver before,
because
>> it is the first driver we try to publish?
> 
> Just publish it as is, and I'll review it publicly. It will
certainly
> take a number of round trips to get it right, if this is your first
> contribution, but that's OK.
>

This MLX90614 driver has a reduced functionality. It was tailored for
our application which use only the temperature read function.
Also the SMBus address is fix defined in the source code, and no
checkes if the factory preprogramming is correct are done.
The option to manage the configuration of the MLX90614 as described in
the datasheets is not yet implemented, because we don't need it.
 
> FYI, I have asked Melexis for an MLX90614 evaluation board, they
have
> sent something to me, so as soon as I receive it I should be able to
> test your driver.
> 

The evalutionboard (EVB) shiped by Melexis uses his own microcontroller
on that board and communicate to the PC via USB. In our system the
MLX90614 sensor is connected directly to the port pins of the
microcontroller.

>> Do plan to include your patch on the "i2c-algo-bit" into the
lastest
>> kernel?
> 
> Yes. Please test the new version of the patch, and if it works OK
for
> you, I'll schedule it for merge in kernel 2.6.38. For 2.6.37 it's
too
> late, the patch is quite intrusive and i2c-algo-bit is used by many
> many drivers including very popular ones, so I can't merge it that
late
> in the release cycle.
> 
>> I had applied the patch and done my tests on the 2.6.25.4 kernel,
with
>> a bunch of other patches needed for my system. 
>> 
>> Thanks a lot for your fast and good support for fixing this issue
we
>> had.
> 
> You're welcome.

Best regards
Matthias Zacharias
matthias.zacharias-zGrmWZs6xXT+aS/vkh9bjw@public.gmane.org

--------------------
BMK electronic solutions GmbH
Werner-von-Siemens-Str. 6, Eingang 18 f
D-86159 Augsburg
Tel. +49 (0) 821 / 207 88 - 700
Fax +49 (0) 821 / 207 88 - 721
info-zGrmWZs6xXT+aS/vkh9bjw@public.gmane.org
Geschäftsführer: Dipl.-oec. Alois Knöferle
Sitz: Augsburg
HR-Nr.: B21197
---------------------

Diese E-mail kann vertrauliche Informationen enthalten. Falls Sie diese
E-Mail irrtümlich erhalten haben, informieren Sie bitte unverzüglich den
Absender und löschen Sie diese E-Mail von jedem Rechner, auch von den
Mailservern. Jede Verbreitung des Inhalts, auch die teilweise
Verbreitung, ist in diesem Fall untersagt. Außer bei Vorsatz oder grober
Fahrlässigkeit schliessen wir jegliche Haftung für Verluste oder Schäden
aus, die durch Viren befallene Software oder E-Mails verursacht werden.

This e-mail may contain confidential information. If you received this
e-mail in error, please contact the sender and delete this e-mail from
your computer, including your mailservers. Any dissemination, even
partly, is prohibited. Except in case of gross negligence or wilful
misconduct we accept no liability for any loss or damage caused by
software or e-mail viruses.

Re: Need help to fix some issues with the linux driver "i2c-gpio"

[Jean Delvare]

On Thu, 16 Dec 2010 11:32:07 +0100, Matthias Zacharias wrote:
> With the new patch the driver is working fine, also with i2c_debug =
> 3.
> 
> See the screenshot in my dropbox
> (http://www.dropbox.com/gallery/16457261/1/I2C_2_MLX90614?h=8e2a46)

Looks good, great. I'll send the patch for review and comments to both
the linux-i2c list and LKML later today.

Do you want me to list you as a tester in the patch header? If I do
that, I'll have to include your name and e-mail address, so I need to
know if this is OK with you.

> > (...)
> > Just publish it as is, and I'll review it publicly. It will
> > certainly take a number of round trips to get it right, if this is
> > your first contribution, but that's OK.
> >
> 
> This MLX90614 driver has a reduced functionality. It was tailored for
> our application which use only the temperature read function.
> Also the SMBus address is fix defined in the source code, and no
> checkes if the factory preprogramming is correct are done.
> The option to manage the configuration of the MLX90614 as described in
> the datasheets is not yet implemented, because we don't need it.

This is totally OK. Others can add functionalities to the driver later
if needed.

> > (...)
> > FYI, I have asked Melexis for an MLX90614 evaluation board, they
> > have sent something to me, so as soon as I receive it I should be
> > able to test your driver.
> 
> The evalutionboard (EVB) shiped by Melexis uses his own microcontroller
> on that board and communicate to the PC via USB. In our system the
> MLX90614 sensor is connected directly to the port pins of the
> microcontroller.

I know that. I don't plan to actually use the micro-controller on the
evaluation board. There are I2C pins on the board, and I'll connect an
external I2C master [1] to them.

[1] http://www.harbaum.org/till/i2c_tiny_usb/index.shtml

-- 
Jean Delvare
http://khali.linux-fr.org/wishlist.html

Antw: Re: Need help to fix some issues with the linux driver "i2c-gpio"

[Matthias Zacharias]

Hello Jean,

>>> Jean Delvare <khali-PUYAD+kWke1g9hUCZPvPmw@public.gmane.org> schrieb am Donnerstag, 16.
Dezember 2010 um
13:52 in Nachricht <20101216135202.38ce671a-R0o5gVi9kd7kN2dkZ6Wm7A@public.gmane.org>:
> On Thu, 16 Dec 2010 11:32:07 +0100, Matthias Zacharias wrote:
>> With the new patch the driver is working fine, also with i2c_debug
=
>> 3.
>> 
>> See the screenshot in my dropbox
>> (http://www.dropbox.com/gallery/16457261/1/I2C_2_MLX90614?h=8e2a46)
> 
> Looks good, great. I'll send the patch for review and comments to
both
> the linux-i2c list and LKML later today.
> 
> Do you want me to list you as a tester in the patch header? If I do
> that, I'll have to include your name and e-mail address, so I need
to
> know if this is OK with you.
> 

Yes it's OK, you can include me as tester, my name and e-mail address
also.

>> > (...)
>> > Just publish it as is, and I'll review it publicly. It will
>> > certainly take a number of round trips to get it right, if this
is
>> > your first contribution, but that's OK.
>> >
>> 
>> This MLX90614 driver has a reduced functionality. It was tailored
for
>> our application which use only the temperature read function.
>> Also the SMBus address is fix defined in the source code, and no
>> checkes if the factory preprogramming is correct are done.
>> The option to manage the configuration of the MLX90614 as described
in
>> the datasheets is not yet implemented, because we don't need it.
> 
> This is totally OK. Others can add functionalities to the driver
later
> if needed.
> 
>> > (...)
>> > FYI, I have asked Melexis for an MLX90614 evaluation board, they
>> > have sent something to me, so as soon as I receive it I should be
>> > able to test your driver.
>> 
>> The evalutionboard (EVB) shiped by Melexis uses his own
microcontroller
>> on that board and communicate to the PC via USB. In our system the
>> MLX90614 sensor is connected directly to the port pins of the
>> microcontroller.
> 
> I know that. I don't plan to actually use the micro-controller on
the
> evaluation board. There are I2C pins on the board, and I'll connect
an
> external I2C master [1] to them.
> 
> [1] http://www.harbaum.org/till/i2c_tiny_usb/index.shtml 

This seems to be an interesting board. I'm impressed that it works also
with a smartphone as frontend.

Best regards
Matthias Zacharias

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