RE: i2c-davinci.c: CPU FREQ causes lock up due to xfr_complete

2014-07-31 Thread Brian Niebuhr 


 -Original Message-
 From: davinci-linux-open-source-boun...@linux.davincidsp.com
 [mailto:davinci-linux-open-source-boun...@linux.davincidsp.com] On
 Behalf Of Jon Cormier
 Sent: Tuesday, July 29, 2014 9:20 AM
 To: davinci-linux-open-source@linux.davincidsp.com
 Cc: Tim Iskander
 Subject: i2c-davinci.c: CPU FREQ causes lock up due to xfr_complete

 Reported issue:

 1. Enable I2C1, flash the new kernel and reboot
 2. Immediately after reboot, attempt to change the processor clock: echo
 456000  /sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed
 3. Process blocks

 However, if we do the following:
 1. Enable I2C1, flash the new kernel and reboot
 2. Immediately after reboot, run: i2cdetect -y 2 0x08 0x08 or just 
 i2cdetect
 -y 2
 3. Then run: echo 456000 
 /sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed
 4. Command succeeds

I found this problem as well, and I haven't had time to put together a proper 
patch.  Right now we're just working around it.  There are several problems 
with the use of a completion for this task:

1. If no I2C transfer has occurred, a cpufreq transition will block forever 
(which is the bug you found)
2. Once an I2C transfer has occurred the cpufreq transition will never block 
since the completion is never reinitialized.
3. Even if you do reinitialize the completion for every I2C transfer, (1) is 
not solved and there is still a race condition where the cpufreq transition 
could start just before an I2C transfer starts and the I2C transfer occurs 
during the cpufreq transition.

Personally I think the correct solution is to use a mutex instead of a 
completion.  The cpufreq code would take the mutex during the prechange 
callback and release it during the postchange callback.  Likewise the I2C 
transfer function would hold the mutex while an I2C transfer is ongoing.  That 
way an I2C transfer cannot occur during a cpufreq transition and vice-versa.  
As I mentioned, I have not had time to put together a proper patch, but I would 
be happy to see this issue addressed if someone else can do it.


 Here's the kernel hung task stack trace:

 INFO: task sh:1428 blocked for more than 120 seconds.
 echo 0  /proc/sys/kernel/hung_task_timeout_secs disables this message.
 sh D c026dc74 0 1428 1426 0x
 [c026dc74] (schedule+0x2a8/0x334) from [c026e2e0]
 (schedule_timeout+0x1c/0x218)
 [c026e2e0] (schedule_timeout+0x1c/0x218) from [c026e164]
 (wait_for_common+0xf0/0x1b8)
 [c026e164] (wait_for_common+0xf0/0x1b8) from [c019ca1c]
 (i2c_davinci_cpufreq_transition+0x18/0x50)
 [c019ca1c] (i2c_davinci_cpufreq_transition+0x18/0x50) from [c00599a4]
 (notifier_call_chain+0x38/0x68)
 [c00599a4] (notifier_call_chain+0x38/0x68) from [c0059a80]
 (__srcu_notifier_call_chain+0x40/0x58)
 [c0059a80] (__srcu_notifier_call_chain+0x40/0x58) from [c0059aac]
 (srcu_notifier_call_chain+0x14/0x18)
 [c0059aac] (srcu_notifier_call_chain+0x14/0x18) from [c019dd78]
 (cpufreq_notify_transition+0xc8/0xfc)
 [c019dd78] (cpufreq_notify_transition+0xc8/0xfc) from [c00373ac]
 (davinci_target+0x144/0x154)
 [c00373ac] (davinci_target+0x144/0x154) from [c019d404]
 (__cpufreq_driver_target+0x28/0x38)
 [c019d404] (__cpufreq_driver_target+0x28/0x38) from [c019f260]
 (cpufreq_set+0x54/0x70)
 [c019f260] (cpufreq_set+0x54/0x70) from [c019d698]
 (store_scaling_setspeed+0x58/0x6c)
 [c019d698] (store_scaling_setspeed+0x58/0x6c) from [c019e3d0]
 (store+0x58/0x74)
 [c019e3d0] (store+0x58/0x74) from [c00d8854]
 (sysfs_write_file+0x108/0x140)
 [c00d8854] (sysfs_write_file+0x108/0x140) from [c009512c]
 (vfs_write+0xb0/0x118)
 [c009512c] (vfs_write+0xb0/0x118) from [c0095244]
 (sys_write+0x3c/0x68)
 [c0095244] (sys_write+0x3c/0x68) from [c002bea0]
 (ret_fast_syscall+0x0/0x28)
 Kernel panic - not syncing: hung_task: blocked tasks
 [c003069c] (unwind_backtrace+0x0/0xd0) from [c026d810]
 (panic+0x44/0xc8)
 [c026d810] (panic+0x44/0xc8) from [c006aa7c] (watchdog+0x1d4/0x21c)
 [c006aa7c] (watchdog+0x1d4/0x21c) from [c0054670]
 (kthread+0x78/0x80)
 [c0054670] (kthread+0x78/0x80) from [c002c8dc]
 (kernel_thread_exit+0x0/0x8)
 According to the stack trace the kernel gets stuck in the
 i2c_davinci_cpufreq_transition function when it calls
 wait_for_completion(dev-xfr_complete);  The two other places this
 xfr_complete variable is referenced is the init_completion in the probe and
 the complete at the end of the i2c_davinci_xfer function. My understanding
 as to what this was intended for was to ensure that a transfer in progress
 completed before changing the clock frequency.  But as its currently done
 the only thing it does is make sure there has been a completed i2c transfer
 on this device ever.  Is my understanding correct?
 Currently the workaround is to simply disable the wait_for_completion as
 seen below.  How would you fix this to ensure a transfer in progress
 completes before changing clocks without hanging if no transfer was ever
 attempted?
 diff --git a/drivers/i2c/busses/i2c-davinci.c

Re: i2c-davinci.c: CPU FREQ causes lock up due to xfr_complete

2014-07-30 Thread Sekhar Nori 
On Tuesday 29 July 2014 11:00 PM, Grygorii Strashko wrote:
 Hi Jon,
 
 On 07/29/2014 06:53 PM, Jon Cormier wrote:
 A slimmer patch suggested by Grygorii Strashko grygorii.stras...@ti.com
 
 
 Ok. The problem seems to be deeper than at first look.
 You have sequence (in Mainline kernel):
 cpufreq:
  |- notify CPUFREQ_PRECHANGE
 |- i2c-davinci will lock  put I2C in reset
  |- cpufreq_driver-target_index
 |- davinci_target()
|- pdata-set_voltage() - It will try to use I2C to set new voltage,
while I2C is in reset or locked! Bug!
  |- notify CPUFREQ_POSTCHANGE
 |- i2c-davinci will re-enable I2C and adjust I2C clock

Good find. I really wonder how this escaped so far. I can swear cpufreq
transitions were tested multiple times. From the description it looks
like this should hit every single time there is a voltage adjustment.

On DA850 which is the only DaVinci implementing cpufreq, I2C0 input
frequency will remain constant across cpufreq transitions since it
derives from PLL0 AUXCLK which is used pre-multipler/divider. It remains
fixed.

The code seems to have been added for I2C1 which does have a fixed ratio
with cpu clock.

PMIC should usually be put on I2C0 to help prevent these kind of issues.

 I see few possible ways to solve it:
 1) use CLK notifier instead of CPUfreq notifiers

This will require common clock framework, right? We dont have that on
mach-davinci.

 2) do smth similar to 61c7cff8 i2c: S3C24XX I2C frequency scaling support
   + 9bcd04bf i2c: s3c2410: grab adapter lock while changing i2c clock

This looks promising. Although I wonder if delta_f will always remain
zero in s3c24xx_i2c_cpufreq_transition() when the CPUFREQ_PRECHANGE call
is made - because clock tree is not updated yet?

 3) update I2C clock in CPUFREQ_POSTCHANGE - may be unsafe

Well, even now the I2C clock is only getting updated in POSTCHANGE,
right? Also, resetting I2C in PRECHANGE seems excessive. It is only
required when changing the prescalar. So you can do:

} else if (val == CPUFREQ_POSTCHANGE) {
davinci_i2c_reset_ctrl(dev, 0);
i2c_davinci_calc_clk_dividers(dev);
davinci_i2c_reset_ctrl(dev, 1);
}

So this along with the i2c_lock_adapter() a la
s3c24xx_i2c_cpufreq_transition() should be the right fix, I guess.

Thanks,
Sekhar
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Re: i2c-davinci.c: CPU FREQ causes lock up due to xfr_complete

2014-07-30 Thread Grygorii Strashko 

On 07/30/2014 09:18 AM, Sekhar Nori wrote:

On Tuesday 29 July 2014 11:00 PM, Grygorii Strashko wrote:

Hi Jon,

On 07/29/2014 06:53 PM, Jon Cormier wrote:

A slimmer patch suggested by Grygorii Strashko grygorii.stras...@ti.com



Ok. The problem seems to be deeper than at first look.
You have sequence (in Mainline kernel):
cpufreq:
  |- notify CPUFREQ_PRECHANGE
 |- i2c-davinci will lock  put I2C in reset
  |- cpufreq_driver-target_index
 |- davinci_target()
|- pdata-set_voltage() - It will try to use I2C to set new voltage,
while I2C is in reset or locked! Bug!
  |- notify CPUFREQ_POSTCHANGE
 |- i2c-davinci will re-enable I2C and adjust I2C clock


Good find. I really wonder how this escaped so far. I can swear cpufreq
transitions were tested multiple times. From the description it looks
like this should hit every single time there is a voltage adjustment.

On DA850 which is the only DaVinci implementing cpufreq, I2C0 input
frequency will remain constant across cpufreq transitions since it
derives from PLL0 AUXCLK which is used pre-multipler/divider. It remains
fixed.

The code seems to have been added for I2C1 which does have a fixed ratio
with cpu clock.

PMIC should usually be put on I2C0 to help prevent these kind of issues.


I see few possible ways to solve it:
1) use CLK notifier instead of CPUfreq notifiers


This will require common clock framework, right? We dont have that on
mach-davinci.


:( I've forgotten about that.




2) do smth similar to 61c7cff8 i2c: S3C24XX I2C frequency scaling support
   + 9bcd04bf i2c: s3c2410: grab adapter lock while changing i2c clock


This looks promising. Although I wonder if delta_f will always remain
zero in s3c24xx_i2c_cpufreq_transition() when the CPUFREQ_PRECHANGE call
is made - because clock tree is not updated yet?


That's funny - seems PRE/POST notifiers are called twice for s3c24xx :)
First one from cpufreq core.
Second time from s3c_cpufreq_target() and, looks like, clock
freq will be updated at that time.





3) update I2C clock in CPUFREQ_POSTCHANGE - may be unsafe


Well, even now the I2C clock is only getting updated in POSTCHANGE,
right? Also, resetting I2C in PRECHANGE seems excessive. It is only
required when changing the prescalar. So you can do:

} else if (val == CPUFREQ_POSTCHANGE) {
davinci_i2c_reset_ctrl(dev, 0);
i2c_davinci_calc_clk_dividers(dev);
davinci_i2c_reset_ctrl(dev, 1);
}

So this along with the i2c_lock_adapter() a la
s3c24xx_i2c_cpufreq_transition() should be the right fix, I guess.



Regards,
-grygorii
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Re: i2c-davinci.c: CPU FREQ causes lock up due to xfr_complete

2014-07-29 Thread Jon Cormier 
Okay here is my attempt.

Author: Cormier, Jonathan jcorm...@criticallink.com
Date:   Tue Jul 29 11:26:22 2014 -0400

i2c: davinci: Change xfr_complete completion to a mutex

There are several problems with the use of a completion for this task:

1. If no I2C transfer has occurred, a cpufreq transition will block forever.
2. Once an I2C transfer has occurred the cpufreq transition will
never block since the completion is never reinitialized.
3. Even if you do reinitialize the completion for every I2C
transfer, (1) is not solved and there is still a race condition where
the cpufreq transition could start just before an I2C transfer starts
and the I2C transfer occurs during the cpufreq transition.

Signed-off-by: Cormier, Jonathan jcorm...@criticallink.com

diff --git a/drivers/i2c/busses/i2c-davinci.c b/drivers/i2c/busses/i2c-davinci.c
index a76d85f..9eac1c1 100644
--- a/drivers/i2c/busses/i2c-davinci.c
+++ b/drivers/i2c/busses/i2c-davinci.c
@@ -111,7 +111,7 @@ struct davinci_i2c_dev {
 u8terminate;
 struct i2c_adapteradapter;
 #ifdef CONFIG_CPU_FREQ
-struct completionxfr_complete;
+struct mutexxfr_lock;
 struct notifier_blockfreq_transition;
 #endif
 };
@@ -438,10 +438,14 @@ i2c_davinci_xfer(struct i2c_adapter *adap,
struct i2c_msg msgs[], int num)

 dev_dbg(dev-dev, %s: msgs: %d\n, __func__, num);

+#ifdef CONFIG_CPU_FREQ
+mutex_lock(dev-xfr_lock);
+#endif
+
 ret = i2c_davinci_wait_bus_not_busy(dev, 1);
 if (ret  0) {
 dev_warn(dev-dev, timeout waiting for bus ready\n);
-return ret;
+goto exit;
 }

 for (i = 0; i  num; i++) {
@@ -449,14 +453,17 @@ i2c_davinci_xfer(struct i2c_adapter *adap,
struct i2c_msg msgs[], int num)
 dev_dbg(dev-dev, %s [%d/%d] ret: %d\n, __func__, i + 1, num,
 ret);
 if (ret  0)
-return ret;
+goto exit;
 }
+ret = num;
+
+exit:

 #ifdef CONFIG_CPU_FREQ
-complete(dev-xfr_complete);
+mutex_unlock(dev-xfr_lock);
 #endif

-return num;
+return ret;
 }

 static u32 i2c_davinci_func(struct i2c_adapter *adap)
@@ -596,11 +603,16 @@ static int i2c_davinci_cpufreq_transition(struct
notifier_block *nb,

 dev = container_of(nb, struct davinci_i2c_dev, freq_transition);
 if (val == CPUFREQ_PRECHANGE) {
-wait_for_completion(dev-xfr_complete);
+#ifdef CONFIG_CPU_FREQ
+mutex_lock(dev-xfr_lock);
+#endif
 davinci_i2c_reset_ctrl(dev, 0);
 } else if (val == CPUFREQ_POSTCHANGE) {
 i2c_davinci_calc_clk_dividers(dev);
 davinci_i2c_reset_ctrl(dev, 1);
+#ifdef CONFIG_CPU_FREQ
+mutex_unlock(dev-xfr_lock);
+#endif
 }

 return 0;
@@ -670,7 +682,7 @@ static int davinci_i2c_probe(struct platform_device *pdev)

 init_completion(dev-cmd_complete);
 #ifdef CONFIG_CPU_FREQ
-init_completion(dev-xfr_complete);
+mutex_init(dev-xfr_lock);
 #endif
 dev-dev = get_device(pdev-dev);
 dev-irq = irq-start;



I'm using the 3.2 branch and the above patch revealed another bug.


INFO: task sh:2144 blocked for more than 120 seconds.
echo 0  /proc/sys/kernel/hung_task_timeout_secs disables this message.
sh  D c03262f0 0  2144   1383 0x
[c03262f0] (__schedule+0x350/0x3b0) from [c03270f4]
(__mutex_lock_slowpath+0
x90/0x100)
[c03270f4] (__mutex_lock_slowpath+0x90/0x100) from [c021dde4]
(i2c_davinci_x
fer+0x30/0x30c)
[c021dde4] (i2c_davinci_xfer+0x30/0x30c) from [c021c310]
(i2c_transfer+0xbc/ 0x110)
[c021c310] (i2c_transfer+0xbc/0x110) from [c021c3e8]
(i2c_master_send+0x38/0
x48)
[c021c3e8] (i2c_master_send+0x38/0x48) from [c01a06f0]
(regmap_i2c_write+0x1
0/0x2c)
[c01a06f0] (regmap_i2c_write+0x10/0x2c) from [c019e584]
(_regmap_raw_write+0
xa4/0x144)
[c019e584] (_regmap_raw_write+0xa4/0x144) from [c019ed44]
(regmap_write+0x24 /0x38)
[c019ed44] (regmap_write+0x24/0x38) from [c01728e0]
(tps65023_dcdc_set_volta
ge+0xc0/0xe8)
[c01728e0] (tps65023_dcdc_set_voltage+0xc0/0xe8) from [c0170efc]
(_regulator
_do_set_voltage+0x3c/0x1d0)
[c0170efc] (_regulator_do_set_voltage+0x3c/0x1d0) from [c0171f74]
(regulator
_set_voltage+0xb8/0xcc)
[c0171f74] (regulator_set_voltage+0xb8/0xcc) from [c0014360]
(davinci_target
+0xcc/0x14c)
[c0014360] (davinci_target+0xcc/0x14c) from [c021e5b8]
(__cpufreq_driver_tar
get+0x2c/0x3c)
[c021e5b8] (__cpufreq_driver_target+0x2c/0x3c) from [c0220328]
(cpufreq_set+ 0x54/0x70)
[c0220328] (cpufreq_set+0x54/0x70) from [c021e9f8]
(store_scaling_setspeed+0
x58/0x6c)
[c021e9f8] (store_scaling_setspeed+0x58/0x6c) from [c021f954]
(store+0x58/0x 70)
[c021f954] (store+0x58/0x70) from [c00cea58] (sysfs_write_file+0x108/0x140)
[c00cea58] (sysfs_write_file+0x108/0x140) from [c0081eb0]
(vfs_write+0xb0/0x 138)

Re: i2c-davinci.c: CPU FREQ causes lock up due to xfr_complete

2014-07-29 Thread Jon Cormier 
A slimmer patch suggested by Grygorii Strashko grygorii.stras...@ti.com

Author: Cormier, Jonathan jcorm...@criticallink.com
Date:   Tue Jul 29 11:50:04 2014 -0400

i2c: davinci: Change xfr_complete completion to use i2c_lock_adapter

There are several problems with the use of a completion for this task:

1. If no I2C transfer has occurred, a cpufreq transition will block forever.
2. Once an I2C transfer has occurred the cpufreq transition will
never block since the completion is never reinitialized.
3. Even if you do reinitialize the completion for every I2C
transfer, (1) is not solved and there is still a race condition where
the cpufreq transition could start just before an I2C transfer starts
and the I2C transfer occurs during the cpufreq transition.

Author: Grygorii Strashko grygorii.stras...@ti.com
Author: Cormier, Jonathan jcorm...@criticallink.com
Signed-off-by: Cormier, Jonathan jcorm...@criticallink.com

diff --git a/drivers/i2c/busses/i2c-davinci.c b/drivers/i2c/busses/i2c-davinci.c
index a76d85f..f8e7b7f 100644
--- a/drivers/i2c/busses/i2c-davinci.c
+++ b/drivers/i2c/busses/i2c-davinci.c
@@ -111,7 +111,6 @@ struct davinci_i2c_dev {
 u8terminate;
 struct i2c_adapteradapter;
 #ifdef CONFIG_CPU_FREQ
-struct completionxfr_complete;
 struct notifier_blockfreq_transition;
 #endif
 };
@@ -452,10 +451,6 @@ i2c_davinci_xfer(struct i2c_adapter *adap, struct
i2c_msg msgs[], int num)
 return ret;
 }

-#ifdef CONFIG_CPU_FREQ
-complete(dev-xfr_complete);
-#endif
-
 return num;
 }

@@ -596,11 +591,12 @@ static int i2c_davinci_cpufreq_transition(struct
notifier_block *nb,

 dev = container_of(nb, struct davinci_i2c_dev, freq_transition);
 if (val == CPUFREQ_PRECHANGE) {
-wait_for_completion(dev-xfr_complete);
+i2c_lock_adapter(dev-adapter);
 davinci_i2c_reset_ctrl(dev, 0);
 } else if (val == CPUFREQ_POSTCHANGE) {
 i2c_davinci_calc_clk_dividers(dev);
 davinci_i2c_reset_ctrl(dev, 1);
+i2c_unlock_adapter(dev-adapter);
 }

 return 0;
@@ -669,9 +665,7 @@ static int davinci_i2c_probe(struct platform_device *pdev)
 }

 init_completion(dev-cmd_complete);
-#ifdef CONFIG_CPU_FREQ
-init_completion(dev-xfr_complete);
-#endif
+
 dev-dev = get_device(pdev-dev);
 dev-irq = irq-start;
 platform_set_drvdata(pdev, dev);

On Tue, Jul 29, 2014 at 11:36 AM, Jon Cormier jcorm...@criticallink.com wrote:
 Okay here is my attempt.

 Author: Cormier, Jonathan jcorm...@criticallink.com
 Date:   Tue Jul 29 11:26:22 2014 -0400

 i2c: davinci: Change xfr_complete completion to a mutex

 There are several problems with the use of a completion for this task:

 1. If no I2C transfer has occurred, a cpufreq transition will block 
 forever.
 2. Once an I2C transfer has occurred the cpufreq transition will
 never block since the completion is never reinitialized.
 3. Even if you do reinitialize the completion for every I2C
 transfer, (1) is not solved and there is still a race condition where
 the cpufreq transition could start just before an I2C transfer starts
 and the I2C transfer occurs during the cpufreq transition.

 Signed-off-by: Cormier, Jonathan jcorm...@criticallink.com

 diff --git a/drivers/i2c/busses/i2c-davinci.c 
 b/drivers/i2c/busses/i2c-davinci.c
 index a76d85f..9eac1c1 100644
 --- a/drivers/i2c/busses/i2c-davinci.c
 +++ b/drivers/i2c/busses/i2c-davinci.c
 @@ -111,7 +111,7 @@ struct davinci_i2c_dev {
  u8terminate;
  struct i2c_adapteradapter;
  #ifdef CONFIG_CPU_FREQ
 -struct completionxfr_complete;
 +struct mutexxfr_lock;
  struct notifier_blockfreq_transition;
  #endif
  };
 @@ -438,10 +438,14 @@ i2c_davinci_xfer(struct i2c_adapter *adap,
 struct i2c_msg msgs[], int num)

  dev_dbg(dev-dev, %s: msgs: %d\n, __func__, num);

 +#ifdef CONFIG_CPU_FREQ
 +mutex_lock(dev-xfr_lock);
 +#endif
 +
  ret = i2c_davinci_wait_bus_not_busy(dev, 1);
  if (ret  0) {
  dev_warn(dev-dev, timeout waiting for bus ready\n);
 -return ret;
 +goto exit;
  }

  for (i = 0; i  num; i++) {
 @@ -449,14 +453,17 @@ i2c_davinci_xfer(struct i2c_adapter *adap,
 struct i2c_msg msgs[], int num)
  dev_dbg(dev-dev, %s [%d/%d] ret: %d\n, __func__, i + 1, num,
  ret);
  if (ret  0)
 -return ret;
 +goto exit;
  }
 +ret = num;
 +
 +exit:

  #ifdef CONFIG_CPU_FREQ
 -complete(dev-xfr_complete);
 +mutex_unlock(dev-xfr_lock);
  #endif

 -return num;
 +return ret;
  }

  static u32 i2c_davinci_func(struct i2c_adapter *adap)
 @@ -596,11 +603,16 @@ static int i2c_davinci_cpufreq_transition(struct
 notifier_block *nb,

  dev = container_of(nb, struct davinci_i2c_dev, freq_transition);
  if (val == CPUFREQ_PRECHANGE) {
 -wait_for_completion(dev-xfr_complete);
 +#ifdef

Re: i2c-davinci.c: CPU FREQ causes lock up due to xfr_complete

2014-07-29 Thread Grygorii Strashko 
Hi Jon,

On 07/29/2014 06:53 PM, Jon Cormier wrote:
 A slimmer patch suggested by Grygorii Strashko grygorii.stras...@ti.com


Ok. The problem seems to be deeper than at first look.
You have sequence (in Mainline kernel):
cpufreq:
 |- notify CPUFREQ_PRECHANGE
|- i2c-davinci will lock  put I2C in reset
 |- cpufreq_driver-target_index
|- davinci_target()
   |- pdata-set_voltage() - It will try to use I2C to set new voltage,
   while I2C is in reset or locked! Bug!
 |- notify CPUFREQ_POSTCHANGE
|- i2c-davinci will re-enable I2C and adjust I2C clock

I see few possible ways to solve it:
1) use CLK notifier instead of CPUfreq notifiers
2) do smth similar to 61c7cff8 i2c: S3C24XX I2C frequency scaling support
  + 9bcd04bf i2c: s3c2410: grab adapter lock while changing i2c clock
3) update I2C clock in CPUFREQ_POSTCHANGE - may be unsafe

Regards,
-grygorii

 
 Author: Cormier, Jonathan jcorm...@criticallink.com
 Date:   Tue Jul 29 11:50:04 2014 -0400
 
  i2c: davinci: Change xfr_complete completion to use i2c_lock_adapter
 
  There are several problems with the use of a completion for this task:
 
  1. If no I2C transfer has occurred, a cpufreq transition will block 
 forever.
  2. Once an I2C transfer has occurred the cpufreq transition will
 never block since the completion is never reinitialized.
  3. Even if you do reinitialize the completion for every I2C
 transfer, (1) is not solved and there is still a race condition where
 the cpufreq transition could start just before an I2C transfer starts
 and the I2C transfer occurs during the cpufreq transition.
 
  Author: Grygorii Strashko grygorii.stras...@ti.com
  Author: Cormier, Jonathan jcorm...@criticallink.com
  Signed-off-by: Cormier, Jonathan jcorm...@criticallink.com
 
 diff --git a/drivers/i2c/busses/i2c-davinci.c 
 b/drivers/i2c/busses/i2c-davinci.c
 index a76d85f..f8e7b7f 100644
 --- a/drivers/i2c/busses/i2c-davinci.c
 +++ b/drivers/i2c/busses/i2c-davinci.c
 @@ -111,7 +111,6 @@ struct davinci_i2c_dev {
   u8terminate;
   struct i2c_adapteradapter;
   #ifdef CONFIG_CPU_FREQ
 -struct completionxfr_complete;
   struct notifier_blockfreq_transition;
   #endif
   };
 @@ -452,10 +451,6 @@ i2c_davinci_xfer(struct i2c_adapter *adap, struct
 i2c_msg msgs[], int num)
   return ret;
   }
 
 -#ifdef CONFIG_CPU_FREQ
 -complete(dev-xfr_complete);
 -#endif
 -
   return num;
   }
 
 @@ -596,11 +591,12 @@ static int i2c_davinci_cpufreq_transition(struct
 notifier_block *nb,
 
   dev = container_of(nb, struct davinci_i2c_dev, freq_transition);
   if (val == CPUFREQ_PRECHANGE) {
 -wait_for_completion(dev-xfr_complete);
 +i2c_lock_adapter(dev-adapter);
   davinci_i2c_reset_ctrl(dev, 0);
   } else if (val == CPUFREQ_POSTCHANGE) {
   i2c_davinci_calc_clk_dividers(dev);
   davinci_i2c_reset_ctrl(dev, 1);
 +i2c_unlock_adapter(dev-adapter);
   }
 
   return 0;
 @@ -669,9 +665,7 @@ static int davinci_i2c_probe(struct platform_device *pdev)
   }
 
   init_completion(dev-cmd_complete);
 -#ifdef CONFIG_CPU_FREQ
 -init_completion(dev-xfr_complete);
 -#endif
 +
   dev-dev = get_device(pdev-dev);
   dev-irq = irq-start;
   platform_set_drvdata(pdev, dev);
 
 On Tue, Jul 29, 2014 at 11:36 AM, Jon Cormier jcorm...@criticallink.com 
 wrote:
 Okay here is my attempt.

 Author: Cormier, Jonathan jcorm...@criticallink.com
 Date:   Tue Jul 29 11:26:22 2014 -0400

  i2c: davinci: Change xfr_complete completion to a mutex

  There are several problems with the use of a completion for this task:

  1. If no I2C transfer has occurred, a cpufreq transition will block 
 forever.
  2. Once an I2C transfer has occurred the cpufreq transition will
 never block since the completion is never reinitialized.
  3. Even if you do reinitialize the completion for every I2C
 transfer, (1) is not solved and there is still a race condition where
 the cpufreq transition could start just before an I2C transfer starts
 and the I2C transfer occurs during the cpufreq transition.

  Signed-off-by: Cormier, Jonathan jcorm...@criticallink.com

 diff --git a/drivers/i2c/busses/i2c-davinci.c 
 b/drivers/i2c/busses/i2c-davinci.c
 index a76d85f..9eac1c1 100644
 --- a/drivers/i2c/busses/i2c-davinci.c
 +++ b/drivers/i2c/busses/i2c-davinci.c
 @@ -111,7 +111,7 @@ struct davinci_i2c_dev {
   u8terminate;
   struct i2c_adapteradapter;
   #ifdef CONFIG_CPU_FREQ
 -struct completionxfr_complete;
 +struct mutexxfr_lock;
   struct notifier_blockfreq_transition;
   #endif
   };
 @@ -438,10 +438,14 @@ i2c_davinci_xfer(struct i2c_adapter *adap,
 struct i2c_msg msgs[], int num)

   dev_dbg(dev-dev, %s: msgs: %d\n, __func__, num);

 +#ifdef CONFIG_CPU_FREQ
 +mutex_lock(dev-xfr_lock);
 +#endif
 +
   ret = i2c_davinci_wait_bus_not_busy(dev, 1);

Re: i2c-davinci.c: CPU FREQ causes lock up due to xfr_complete

2014-07-29 Thread Jon Cormier 
Grygorii,

Unfortunately I don't have access to a booting mainline kernel to try
and work on this.  Its also currently a bit over my head.

cheers,
-Jonathan

On Tue, Jul 29, 2014 at 1:30 PM, Grygorii Strashko
grygorii.stras...@ti.com wrote:
 Hi Jon,

 On 07/29/2014 06:53 PM, Jon Cormier wrote:
 A slimmer patch suggested by Grygorii Strashko grygorii.stras...@ti.com


 Ok. The problem seems to be deeper than at first look.
 You have sequence (in Mainline kernel):
 cpufreq:
  |- notify CPUFREQ_PRECHANGE
 |- i2c-davinci will lock  put I2C in reset
  |- cpufreq_driver-target_index
 |- davinci_target()
|- pdata-set_voltage() - It will try to use I2C to set new voltage,
while I2C is in reset or locked! Bug!
  |- notify CPUFREQ_POSTCHANGE
 |- i2c-davinci will re-enable I2C and adjust I2C clock

 I see few possible ways to solve it:
 1) use CLK notifier instead of CPUfreq notifiers
 2) do smth similar to 61c7cff8 i2c: S3C24XX I2C frequency scaling support
   + 9bcd04bf i2c: s3c2410: grab adapter lock while changing i2c clock
 3) update I2C clock in CPUFREQ_POSTCHANGE - may be unsafe

 Regards,
 -grygorii


 Author: Cormier, Jonathan jcorm...@criticallink.com
 Date:   Tue Jul 29 11:50:04 2014 -0400

  i2c: davinci: Change xfr_complete completion to use i2c_lock_adapter

  There are several problems with the use of a completion for this task:

  1. If no I2C transfer has occurred, a cpufreq transition will block 
 forever.
  2. Once an I2C transfer has occurred the cpufreq transition will
 never block since the completion is never reinitialized.
  3. Even if you do reinitialize the completion for every I2C
 transfer, (1) is not solved and there is still a race condition where
 the cpufreq transition could start just before an I2C transfer starts
 and the I2C transfer occurs during the cpufreq transition.

  Author: Grygorii Strashko grygorii.stras...@ti.com
  Author: Cormier, Jonathan jcorm...@criticallink.com
  Signed-off-by: Cormier, Jonathan jcorm...@criticallink.com

 diff --git a/drivers/i2c/busses/i2c-davinci.c 
 b/drivers/i2c/busses/i2c-davinci.c
 index a76d85f..f8e7b7f 100644
 --- a/drivers/i2c/busses/i2c-davinci.c
 +++ b/drivers/i2c/busses/i2c-davinci.c
 @@ -111,7 +111,6 @@ struct davinci_i2c_dev {
   u8terminate;
   struct i2c_adapteradapter;
   #ifdef CONFIG_CPU_FREQ
 -struct completionxfr_complete;
   struct notifier_blockfreq_transition;
   #endif
   };
 @@ -452,10 +451,6 @@ i2c_davinci_xfer(struct i2c_adapter *adap, struct
 i2c_msg msgs[], int num)
   return ret;
   }

 -#ifdef CONFIG_CPU_FREQ
 -complete(dev-xfr_complete);
 -#endif
 -
   return num;
   }

 @@ -596,11 +591,12 @@ static int i2c_davinci_cpufreq_transition(struct
 notifier_block *nb,

   dev = container_of(nb, struct davinci_i2c_dev, freq_transition);
   if (val == CPUFREQ_PRECHANGE) {
 -wait_for_completion(dev-xfr_complete);
 +i2c_lock_adapter(dev-adapter);
   davinci_i2c_reset_ctrl(dev, 0);
   } else if (val == CPUFREQ_POSTCHANGE) {
   i2c_davinci_calc_clk_dividers(dev);
   davinci_i2c_reset_ctrl(dev, 1);
 +i2c_unlock_adapter(dev-adapter);
   }

   return 0;
 @@ -669,9 +665,7 @@ static int davinci_i2c_probe(struct platform_device 
 *pdev)
   }

   init_completion(dev-cmd_complete);
 -#ifdef CONFIG_CPU_FREQ
 -init_completion(dev-xfr_complete);
 -#endif
 +
   dev-dev = get_device(pdev-dev);
   dev-irq = irq-start;
   platform_set_drvdata(pdev, dev);

 On Tue, Jul 29, 2014 at 11:36 AM, Jon Cormier jcorm...@criticallink.com 
 wrote:
 Okay here is my attempt.

 Author: Cormier, Jonathan jcorm...@criticallink.com
 Date:   Tue Jul 29 11:26:22 2014 -0400

  i2c: davinci: Change xfr_complete completion to a mutex

  There are several problems with the use of a completion for this task:

  1. If no I2C transfer has occurred, a cpufreq transition will block 
 forever.
  2. Once an I2C transfer has occurred the cpufreq transition will
 never block since the completion is never reinitialized.
  3. Even if you do reinitialize the completion for every I2C
 transfer, (1) is not solved and there is still a race condition where
 the cpufreq transition could start just before an I2C transfer starts
 and the I2C transfer occurs during the cpufreq transition.

  Signed-off-by: Cormier, Jonathan jcorm...@criticallink.com

 diff --git a/drivers/i2c/busses/i2c-davinci.c 
 b/drivers/i2c/busses/i2c-davinci.c
 index a76d85f..9eac1c1 100644
 --- a/drivers/i2c/busses/i2c-davinci.c
 +++ b/drivers/i2c/busses/i2c-davinci.c
 @@ -111,7 +111,7 @@ struct davinci_i2c_dev {
   u8terminate;
   struct i2c_adapteradapter;
   #ifdef CONFIG_CPU_FREQ
 -struct completionxfr_complete;
 +struct mutexxfr_lock;
   struct notifier_blockfreq_transition;
   #endif
   };
 @@ -438,10 +438,14 @@