kernel oops for 3430sdp

kernel oops for 3430sdp

[Aguirre Rodriguez, Sergio Alberto]

Hi all,

I attempted to run a kernel image in my 3430sdp compiled with the latest commit. I performed these steps:

1.- Loaded omap_3430sdp_defconfig
2.- Entered menuconfig and I added the option:

Device Drivers --->
	GPIO support --->
		<*>   TWL4030/TPS659x0 GPIO Driver

3.- compiled it and loaded in my 3430SDP with u-boot

4.- Booted and got a kernel Oops:

<6>musb_hdrc: version 6.0, musb-dma, otg (peripheral+host), debug=0
<1>Unable to handle kernel NULL pointer dereference at virtual address 00000000
<1>pgd = c0004000
<1>[00000000] *pgd=00000000
Internal error: Oops: 5 [#1]
Modules linked in:
CPU: 0    Not tainted  (2.6.27-rc8-omap1-05072-gf9ceca7 #6)
PC is at musb_platform_init+0x24/0x120
LR is at 0x0
pc : [<c001df5c>]    lr : [<00000000>]    psr: a0000013
sp : c681dd50  ip : c68281b4  fp : c681dd64
r10: c001d288  r9 : 00000000  r8 : c0374b08
r7 : c037950c  r6 : c68280d8  r5 : 00000000  r4 : c68280d8
r3 : c035fba4  r2 : 00000000  r1 : c681dcf8  r0 : 00000000
Flags: NzCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment kernel
Control: 00c5387f  Table: 80004018  DAC: 00000017
Process swapper (pid: 1, stack limit = 0xc681c2e0)
Stack: (0xc681dd50 to 0xc681e000)
dd40:                                     c0362d34 00000000 c681de44 c681dd68
dd60: c001d634 c001df44 00000000 c036d050 c681dd9c c681dd80 c029c10c c0362b90
dd80: c0362b98 0000005c d80ab000 c0362cb8 c681ddac c681dda0 c029c16c c029c07c
dda0: c681ddec c681ddb0 c00dd55c c029c168 c00dd294 c00dd170 c68621b8 c6862158
ddc0: c681ddf0 c6832548 c681ddec 00000000 c6862158 c681ddf0 c6832548 00000001
dde0: c681de24 c681ddf0 c00de1d0 c00dd54c c6832548 00000000 00000000 00000001
de00: c681de44 c0362b98 00000000 c0362c00 c037950c c0374b08 c681de34 c0362b98
de20: c0362c44 c037950c c037950c c0374b08 00000000 c001d288 c681de54 c681de48
de40: c01a7298 c001d438 c681de74 c681de58 c01a6530 c01a7284 c0362b98 c0362c44
de60: c037950c c037950c c681de94 c681de78 c01a6628 c01a646c 00000000 c681de9c
de80: c01a65dc c037950c c681dec4 c681de98 c01a5ba8 c01a65e8 00000000 c6803d58
dea0: c6803d58 c0362be0 00000000 c037950c 00000000 c684c660 c681ded4 c681dec8
dec0: c01a6378 c01a5b68 c681df04 c681ded8 c01a6034 c01a6364 c02afc98 c037950c
dee0: 00000000 c037f380 c037950c 00000000 00000000 00000000 c681df2c c681df08
df00: c01a681c c01a5f98 c037f380 c03794ec 00000000 00000000 00000000 c001d288
df20: c681df3c c681df30 c01a7630 c01a6790 c681df54 c681df40 c01a7664 c01a75c4
df40: c037f380 c0025454 c681df64 c681df58 c001d2c4 c01a7658 c681dfdc c681df68
df60: c002d298 c001d294 c681df94 c681df78 c00d7800 c00d75bc c681df94 c683e260
df80: c00d7944 c681df9e c681dfc4 c681df98 c0077dfc c00d77d4 c681dfb4 3533cd28
dfa0: 00000031 00000000 00000192 c0025454 00000000 c0025524 c0025454 00000000
dfc0: 00000000 00000000 00000000 00000000 c681dff4 c681dfe0 c00088d4 c002d254
dfe0: 00000000 00000000 00000000 c681dff8 c005468c c0008870 124a023d 8e0b1e5e
Backtrace:
[<c001df38>] (musb_platform_init+0x0/0x120) from [<c001d634>] (musb_probe+0x208/0xb0c)
 r5:00000000 r4:c0362d34
[<c001d42c>] (musb_probe+0x0/0xb0c) from [<c01a7298>] (platform_drv_probe+0x20/0x24)
[<c01a7278>] (platform_drv_probe+0x0/0x24) from [<c01a6530>] (driver_probe_device+0xd0/0x17c)
[<c01a6460>] (driver_probe_device+0x0/0x17c) from [<c01a6628>] (__driver_attach+0x4c/0x70)
 r7:c037950c r6:c037950c r5:c0362c44 r4:c0362b98
[<c01a65dc>] (__driver_attach+0x0/0x70) from [<c01a5ba8>] (bus_for_each_dev+0x4c/0x84)
 r7:c037950c r6:c01a65dc r5:c681de9c r4:00000000
[<c01a5b5c>] (bus_for_each_dev+0x0/0x84) from [<c01a6378>] (driver_attach+0x20/0x28)
 r7:c684c660 r6:00000000 r5:c037950c r4:00000000
[<c01a6358>] (driver_attach+0x0/0x28) from [<c01a6034>] (bus_add_driver+0xa8/0x214)
[<c01a5f8c>] (bus_add_driver+0x0/0x214) from [<c01a681c>] (driver_register+0x98/0x120)
 r8:00000000 r7:00000000 r6:00000000 r5:c037950c r4:c037f380
[<c01a6784>] (driver_register+0x0/0x120) from [<c01a7630>] (platform_driver_register+0x78/0x94)
[<c01a75b8>] (platform_driver_register+0x0/0x94) from [<c01a7664>] (platform_driver_probe+0x18/0x68)
[<c01a764c>] (platform_driver_probe+0x0/0x68) from [<c001d2c4>] (musb_init+0x3c/0x54)
 r5:c0025454 r4:c037f380
[<c001d288>] (musb_init+0x0/0x54) from [<c002d298>] (__exception_text_end+0x50/0x17c)
[<c002d248>] (__exception_text_end+0x0/0x17c) from [<c00088d4>] (kernel_init+0x70/0xdc)
[<c0008864>] (kernel_init+0x0/0xdc) from [<c005468c>] (do_exit+0x0/0x6b8)
 r5:00000000 r4:00000000
Code: e5943000 e284c0dc e3530000 e1a0e000 (e8be000f)
<4>---[ end trace 1b75b31a2719ed1c ]---
<0>Kernel panic - not syncing: Attempted to kill init!

Is someone else seeing this?

Regards,
Sergio

Re: kernel oops for 3430sdp

[David Brownell]

On Tuesday 07 October 2008, Aguirre Rodriguez, Sergio Alberto wrote:
> <1>Unable to handle kernel NULL pointer dereference at virtual address 00000000

Did you try with the hack I've sent, to work around one problematic
(and surprisingly reproducible!) i2c-omap timeout?  Appended.

Given I2C faults, many things blow up rudely ... hardly any I2C
drivers are written to tolerate transfer errors.  Not entirely
unreasonably, since such errors are otherwise quite rare.


I currently suspect there's an issue where the i2c-omap code can
handle a bunch of requests that group closely together ... or are
separated by a lot of time ... but there's some middle ground
where if you wait the "right" amount of time before making the
next request, it times out instead of working correctly.

I have no proof behind that theory, but it does seem to match up
to a few of the observed facts.  Notably that the i2c timeouts
appear when the only device on that bus is the TWL4030, and the
drivers make known-to-be-valid requets ... the timeouts started
to appear only after some trivial changes in init timings, which
were caused by moving code out of drivers/i2c into directories
that are more appropriate.

- Dave


---
 drivers/i2c/chips/twl4030-pwrirq.c |   10 ++++++++++
 1 file changed, 10 insertions(+)

--- a/drivers/i2c/chips/twl4030-pwrirq.c
+++ b/drivers/i2c/chips/twl4030-pwrirq.c
@@ -161,6 +161,8 @@ static int twl4030_pwrirq_thread(void *d
 	return 0;
 }
 
+#include <linux/delay.h>
+
 static int __init twl4030_pwrirq_init(void)
 {
 	int i, err;
@@ -168,8 +170,16 @@ static int __init twl4030_pwrirq_init(vo
 	twl4030_pwrirq_mask = 0xff;
 	twl4030_pwrirq_pending_unmask = 0;
 
+/* HEY:  core already did this.
+ * But that's surely not why we
+ * sometimes see timeouts here ...
+ */
+for (i = 0; i < 5; i++) {
 	err = twl4030_i2c_write_u8(TWL4030_MODULE_INT, twl4030_pwrirq_mask,
 					TWL4030_INT_PWR_IMR1);
+if (!err) break;
+msleep(10);
+}
 	if (err)
 		return err;
 

RE: kernel oops for 3430sdp

[Aguirre Rodriguez, Sergio Alberto]

Thanks for that, it worked fine now.

> -----Original Message-----
> From: David Brownell [mailto:david-b@pacbell.net]
> Sent: Tuesday, October 07, 2008 1:29 PM
> To: Aguirre Rodriguez, Sergio Alberto
> Cc: linux-omap@vger.kernel.org
> Subject: Re: kernel oops for 3430sdp
> 
> On Tuesday 07 October 2008, Aguirre Rodriguez, Sergio Alberto wrote:
> > <1>Unable to handle kernel NULL pointer dereference at virtual address
> 00000000
> 
> Did you try with the hack I've sent, to work around one problematic
> (and surprisingly reproducible!) i2c-omap timeout?  Appended.
> 
> Given I2C faults, many things blow up rudely ... hardly any I2C
> drivers are written to tolerate transfer errors.  Not entirely
> unreasonably, since such errors are otherwise quite rare.
> 
> 
> I currently suspect there's an issue where the i2c-omap code can
> handle a bunch of requests that group closely together ... or are
> separated by a lot of time ... but there's some middle ground
> where if you wait the "right" amount of time before making the
> next request, it times out instead of working correctly.
> 
> I have no proof behind that theory, but it does seem to match up
> to a few of the observed facts.  Notably that the i2c timeouts
> appear when the only device on that bus is the TWL4030, and the
> drivers make known-to-be-valid requets ... the timeouts started
> to appear only after some trivial changes in init timings, which
> were caused by moving code out of drivers/i2c into directories
> that are more appropriate.
> 
> - Dave
> 
> 
> ---
>  drivers/i2c/chips/twl4030-pwrirq.c |   10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> --- a/drivers/i2c/chips/twl4030-pwrirq.c
> +++ b/drivers/i2c/chips/twl4030-pwrirq.c
> @@ -161,6 +161,8 @@ static int twl4030_pwrirq_thread(void *d
>  	return 0;
>  }
> 
> +#include <linux/delay.h>
> +
>  static int __init twl4030_pwrirq_init(void)
>  {
>  	int i, err;
> @@ -168,8 +170,16 @@ static int __init twl4030_pwrirq_init(vo
>  	twl4030_pwrirq_mask = 0xff;
>  	twl4030_pwrirq_pending_unmask = 0;
> 
> +/* HEY:  core already did this.
> + * But that's surely not why we
> + * sometimes see timeouts here ...
> + */
> +for (i = 0; i < 5; i++) {
>  	err = twl4030_i2c_write_u8(TWL4030_MODULE_INT, twl4030_pwrirq_mask,
>  					TWL4030_INT_PWR_IMR1);
> +if (!err) break;
> +msleep(10);
> +}
>  	if (err)
>  		return err;
> 
> 

Re: kernel oops for 3430sdp

[Felipe Balbi]

On Tue, Oct 07, 2008 at 11:28:52AM -0700, David Brownell wrote:
> On Tuesday 07 October 2008, Aguirre Rodriguez, Sergio Alberto wrote:
> > <1>Unable to handle kernel NULL pointer dereference at virtual address 00000000
> 
> Did you try with the hack I've sent, to work around one problematic
> (and surprisingly reproducible!) i2c-omap timeout?  Appended.
> 
> Given I2C faults, many things blow up rudely ... hardly any I2C
> drivers are written to tolerate transfer errors.  Not entirely
> unreasonably, since such errors are otherwise quite rare.
> 
> 
> I currently suspect there's an issue where the i2c-omap code can
> handle a bunch of requests that group closely together ... or are
> separated by a lot of time ... but there's some middle ground
> where if you wait the "right" amount of time before making the
> next request, it times out instead of working correctly.
> 
> I have no proof behind that theory, but it does seem to match up
> to a few of the observed facts.  Notably that the i2c timeouts
> appear when the only device on that bus is the TWL4030, and the
> drivers make known-to-be-valid requets ... the timeouts started
> to appear only after some trivial changes in init timings, which
> were caused by moving code out of drivers/i2c into directories
> that are more appropriate.

I was debugging the i2c-omap.c today but so far no clue why that i2c
timeout is coming. It's really weird that it only fails on twl4030-usb
(well, actually pwrirq and twl4030-usb fails since it can't
request_irq).

-- 
balbi

[PATCH] twl4030: Fix pwrirq by making sure the module is responding (Re: kernel oops for 3430sdp)

[Tony Lindgren]

[-- Attachment #1: Type: text/plain, Size: 1862 bytes --]

* Felipe Balbi <me@felipebalbi.com> [081008 06:13]:
> On Tue, Oct 07, 2008 at 11:28:52AM -0700, David Brownell wrote:
> > On Tuesday 07 October 2008, Aguirre Rodriguez, Sergio Alberto wrote:
> > > <1>Unable to handle kernel NULL pointer dereference at virtual address 00000000
> > 
> > Did you try with the hack I've sent, to work around one problematic
> > (and surprisingly reproducible!) i2c-omap timeout?  Appended.
> > 
> > Given I2C faults, many things blow up rudely ... hardly any I2C
> > drivers are written to tolerate transfer errors.  Not entirely
> > unreasonably, since such errors are otherwise quite rare.
> > 
> > 
> > I currently suspect there's an issue where the i2c-omap code can
> > handle a bunch of requests that group closely together ... or are
> > separated by a lot of time ... but there's some middle ground
> > where if you wait the "right" amount of time before making the
> > next request, it times out instead of working correctly.
> > 
> > I have no proof behind that theory, but it does seem to match up
> > to a few of the observed facts.  Notably that the i2c timeouts
> > appear when the only device on that bus is the TWL4030, and the
> > drivers make known-to-be-valid requets ... the timeouts started
> > to appear only after some trivial changes in init timings, which
> > were caused by moving code out of drivers/i2c into directories
> > that are more appropriate.
> 
> I was debugging the i2c-omap.c today but so far no clue why that i2c
> timeout is coming. It's really weird that it only fails on twl4030-usb
> (well, actually pwrirq and twl4030-usb fails since it can't
> request_irq).

I suspect that twl is not yet initialized for pwrirq handling at this
point. At least this patch seems to help, no idea on what registers
we should check though.. Anybody got ideas on what needs to be checked
for pwrirq?

Tony

[-- Attachment #2: twl-pwrirq-hack.patch --]
[-- Type: text/x-diff, Size: 1107 bytes --]

>From f5766a9dbd845911f7bf87bbc71437964b2cc91a Mon Sep 17 00:00:00 2001
From: Tony Lindgren <tony@atomide.com>
Date: Wed, 8 Oct 2008 17:22:30 +0300
Subject: [PATCH] twl4030: Fix pwrirq by making sure the module is responding

Something needs to be checked with twl pwriq module before
trying to use it. Not yet sure what should be checked though..
At least PWR_IMR1 seems to change from 0x0 after few reads.

diff --git a/drivers/i2c/chips/twl4030-pwrirq.c b/drivers/i2c/chips/twl4030-pwrirq.c
index ce66dd4..fd17c3e 100644
--- a/drivers/i2c/chips/twl4030-pwrirq.c
+++ b/drivers/i2c/chips/twl4030-pwrirq.c
@@ -130,10 +130,19 @@ static int twl4030_pwrirq_thread(void *data)
 
 static int __init twl4030_pwrirq_init(void)
 {
-	int i, err;
+	int i = 10, err;
+	u8 tmp;
 
 	twl4030_pwrirq_mask = 0xff;
 
+	/* Wait for other the module to start responding */
+	while (i--) {
+		err = twl4030_i2c_read_u8(TWL4030_MODULE_INT, &tmp,
+						TWL4030_INT_PWR_IMR1);
+		if ((tmp & 0xf) != 0)
+			break;
+	}
+
 	err = twl4030_i2c_write_u8(TWL4030_MODULE_INT, twl4030_pwrirq_mask,
 					TWL4030_INT_PWR_IMR1);
 	if (err)

Re: [PATCH] twl4030: Fix pwrirq by making sure the module is responding (Re: kernel oops for 3430sdp)

[David Brownell]

On Wednesday 08 October 2008, Tony Lindgren wrote:
> I suspect that twl is not yet initialized for pwrirq handling at this
> point. At least this patch seems to help, 

Did you verify that the value you read isn't 0xff?  Or does the
issue seem to be the mere attempt to read a register?

I have a hard time seeing the root cause be anything other than
problems in i2c-omap, since the timeouts appear at various other
places too.


> no idea on what registers 
> we should check though.. Anybody got ideas on what needs to be checked
> for pwrirq?

Well, there does seem to be an issue where the "pending IRQ" mechanism
can leave a PWRIRQ.PWRON interrupt pending sometimes.  If you see a
bunch of alarming-but-harmless boot messages like 

  TWL4030 module irq 373 is disabled but can't be masked!

before pwrirq registers, that seems to be the issue.  A debug hack I
applied (appended) reported that the mask (IMR) was 0xff but the IRQ
was still being raised ... when pwrirq registered itself, the stream
of those messages stopped.  (Or, when this hack dumped the status and
thus kicked in clear-on-read ...)

- Dave


=============================
---
 drivers/mfd/twl4030-core.c |   40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

--- a/drivers/mfd/twl4030-core.c
+++ b/drivers/mfd/twl4030-core.c
@@ -574,6 +574,36 @@ static int twl4030_irq_thread(void *data
 			continue;
 		}
 
+		/* power irq before handler registered? */
+		if ((pih_isr & BIT(5)) && irq_desc[twl4030_irq_base + 5].depth) {
+			u8 buf[8];
+			int status;
+			int retries = 3;
+
+			while (retries--) {
+				status = twl4030_i2c_read(TWL4030_MODULE_INT,
+						buf, 0, sizeof buf);
+				if (status == 0) {
+					pr_crit("... PWR: "
+						"%02x.%02x/%02x.%02x "
+						"%02x; "
+						"%02x.%02x, "
+						"%02x "
+						"\n",
+						/* {ISR,IMR}{1,2} */
+						buf[0], buf[1], buf[2], buf[3],
+						/* SIH */
+						buf[4],
+						/* EDR */
+						buf[5], buf[6],
+						/* CTRL */
+						buf[7]);
+				} else
+					pr_crit("... read PWR --> %d\n",
+						status);
+			}
+		}
+
 		/* these handlers deal with the relevant SIH irq status */
 		local_irq_disable();
 		for (module_irq = twl4030_irq_base;

Re: [PATCH] twl4030: Fix pwrirq by making sure the module is responding (Re: kernel oops for 3430sdp)

[Tony Lindgren]

* David Brownell <david-b@pacbell.net> [081008 21:33]:
> On Wednesday 08 October 2008, Tony Lindgren wrote:
> > I suspect that twl is not yet initialized for pwrirq handling at this
> > point. At least this patch seems to help, 
> 
> Did you verify that the value you read isn't 0xff?  Or does the
> issue seem to be the mere attempt to read a register?

Yeah, it seems to be 0 first, then 0xf0, then 0xf7, then 0xff. It seems
that at 0xf0 it still does not work. Values from memory, but something
like that anyways.

> I have a hard time seeing the root cause be anything other than
> problems in i2c-omap, since the timeouts appear at various other
> places too.

Well at least one twl bug was happening when the source clock was
initialized incorrectly.. And that only happened with one of the twl
modules.

> > no idea on what registers 
> > we should check though.. Anybody got ideas on what needs to be checked
> > for pwrirq?
> 
> Well, there does seem to be an issue where the "pending IRQ" mechanism
> can leave a PWRIRQ.PWRON interrupt pending sometimes.  If you see a
> bunch of alarming-but-harmless boot messages like 
> 
>   TWL4030 module irq 373 is disabled but can't be masked!
> 
> before pwrirq registers, that seems to be the issue.  A debug hack I
> applied (appended) reported that the mask (IMR) was 0xff but the IRQ
> was still being raised ... when pwrirq registered itself, the stream
> of those messages stopped.  (Or, when this hack dumped the status and
> thus kicked in clear-on-read ...)

Hmm, maybe there's some status register for each modules that should be
checked?

Tony

> 
> - Dave
> 
> 
> =============================
> ---
>  drivers/mfd/twl4030-core.c |   40 ++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 40 insertions(+)
> 
> --- a/drivers/mfd/twl4030-core.c
> +++ b/drivers/mfd/twl4030-core.c
> @@ -574,6 +574,36 @@ static int twl4030_irq_thread(void *data
>  			continue;
>  		}
>  
> +		/* power irq before handler registered? */
> +		if ((pih_isr & BIT(5)) && irq_desc[twl4030_irq_base + 5].depth) {
> +			u8 buf[8];
> +			int status;
> +			int retries = 3;
> +
> +			while (retries--) {
> +				status = twl4030_i2c_read(TWL4030_MODULE_INT,
> +						buf, 0, sizeof buf);
> +				if (status == 0) {
> +					pr_crit("... PWR: "
> +						"%02x.%02x/%02x.%02x "
> +						"%02x; "
> +						"%02x.%02x, "
> +						"%02x "
> +						"\n",
> +						/* {ISR,IMR}{1,2} */
> +						buf[0], buf[1], buf[2], buf[3],
> +						/* SIH */
> +						buf[4],
> +						/* EDR */
> +						buf[5], buf[6],
> +						/* CTRL */
> +						buf[7]);
> +				} else
> +					pr_crit("... read PWR --> %d\n",
> +						status);
> +			}
> +		}
> +
>  		/* these handlers deal with the relevant SIH irq status */
>  		local_irq_disable();
>  		for (module_irq = twl4030_irq_base;
> 
> --
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Re: [PATCH] twl4030: Fix pwrirq by making sure the module is responding (Re: kernel oops for 3430sdp)

[David Brownell]

On Wednesday 08 October 2008, Tony Lindgren wrote:
> > 
> > Well, there does seem to be an issue where the "pending IRQ" mechanism
> > can leave a PWRIRQ.PWRON interrupt pending sometimes.  If you see a
> > bunch of alarming-but-harmless boot messages like 
> > 
> >   TWL4030 module irq 373 is disabled but can't be masked!
> > 
> > before pwrirq registers, that seems to be the issue.  A debug hack I
> > applied (appended) reported that the mask (IMR) was 0xff but the IRQ
> > was still being raised ... when pwrirq registered itself, the stream
> > of those messages stopped.  (Or, when this hack dumped the status and
> > thus kicked in clear-on-read ...)
> 
> Hmm, maybe there's some status register for each modules that should be
> checked?

I think this was just a natural consequence of PENDDIS=0 in the
SIH_CTRL register.  A minor annoyance in the init sequence since
it causes extra IRQs, but nothing significant.

I haven't come across a TWL register that could explain I2C
timeouts.  At least, not yet.

- Dave

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Re: [PATCH] twl4030: Fix pwrirq by making sure the module is responding (Re: kernel oops for 3430sdp)

[David Brownell]

On Wednesday 08 October 2008, Tony Lindgren wrote:
> > > I suspect that twl is not yet initialized for pwrirq handling at this
> > > point. At least this patch seems to help, 
> > 
> > Did you verify that the value you read isn't 0xff?  Or does the
> > issue seem to be the mere attempt to read a register?
> 
> Yeah, it seems to be 0 first, then 0xf0, then 0xf7, then 0xff. It seems
> that at 0xf0 it still does not work. Values from memory, but something
> like that anyways.

Huh.  Most bizarre.  Oh wait ... that might be explained by
taking a ginormous amount of time to shift out of the 1.5 MHz
clock mode.  See 3.4.12 of the manual:

  When power is first applied to the device, it does not know
  the external HF clock frequency (HFCLK_FREQ has not been set
  by the host processor). To ensure that the power subchip
  registers can be accessed, the default register access
  frequency is 1.5 MHz (1⁄2 of 3 MHz).

Doesn't say how to tell that's happening, or how long it'd take
to change to 3 MHz.  (Which only happens if HFCLK isn't 19.2 MHz.)
Maybe wait for BACKUP_MISC_CFG.PWR_CLK_FREQ to clear... it's
just controlling a simple divide-by-two, not a PLL, so it should
be pretty much immediate.


> > I have a hard time seeing the root cause be anything other than
> > problems in i2c-omap, since the timeouts appear at various other
> > places too.
> 
> Well at least one twl bug was happening when the source clock was
> initialized incorrectly.. And that only happened with one of the twl
> modules.

The issue above?  But we know that HFCLK_FREQ is getting set,
so that wouldn't explain i2c-omap timeouts that show up later.

Or maybe there's another clocking issue...

I hate to look at the i2c-omap, but it really seems like that's
got to be the root cause here.  After all, the timeout message
appears way too quickly for it to be a *legitimate* timeout for
any I2C protocol action.  (SMBus has timeouts.  I2C doesn't...)

- Dave

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[PATCH 2.6.27-rc9-omap] i2c-omap: timeouts begone

[David Brownell]

I can tell someone's going to want a fix that's a
lot more power-aware ... ;)

This seems to remove the need for the "hack" patch.


--- a/drivers/i2c/busses/i2c-omap.c
+++ b/drivers/i2c/busses/i2c-omap.c
@@ -202,6 +202,9 @@ static void omap_i2c_put_clocks(struct omap_i2c_dev *dev)
 
 static void omap_i2c_unidle(struct omap_i2c_dev *dev)
 {
+	if (1)
+		return;
+
 	if (dev->iclk != NULL)
 		clk_enable(dev->iclk);
 	clk_enable(dev->fclk);
@@ -214,6 +217,9 @@ static void omap_i2c_idle(struct omap_i2c_dev *dev)
 {
 	u16 iv;
 
+	if (1)
+		return;
+
 	dev->iestate = omap_i2c_read_reg(dev, OMAP_I2C_IE_REG);
 	omap_i2c_write_reg(dev, OMAP_I2C_IE_REG, 0);
 	if (dev->rev1)

Re: [PATCH 2.6.27-rc9-omap] i2c-omap: timeouts begone

[Felipe Balbi]

On Wed, Oct 08, 2008 at 02:36:05PM -0700, David Brownell wrote:
> I can tell someone's going to want a fix that's a
> lot more power-aware ... ;)
> 
> This seems to remove the need for the "hack" patch.
> 
> 
> --- a/drivers/i2c/busses/i2c-omap.c
> +++ b/drivers/i2c/busses/i2c-omap.c
> @@ -202,6 +202,9 @@ static void omap_i2c_put_clocks(struct omap_i2c_dev *dev)
>  
>  static void omap_i2c_unidle(struct omap_i2c_dev *dev)
>  {
> +	if (1)
> +		return;
> +
>  	if (dev->iclk != NULL)
>  		clk_enable(dev->iclk);
>  	clk_enable(dev->fclk);
> @@ -214,6 +217,9 @@ static void omap_i2c_idle(struct omap_i2c_dev *dev)
>  {
>  	u16 iv;
>  
> +	if (1)
> +		return;
> +
>  	dev->iestate = omap_i2c_read_reg(dev, OMAP_I2C_IE_REG);
>  	omap_i2c_write_reg(dev, OMAP_I2C_IE_REG, 0);
>  	if (dev->rev1)


At least we can say the problem seems to be related to pm. Maybe after
context restore we should wait until the clock stabilizes or some
register changes ??

-- 
balbi

RE: [PATCH 2.6.27-rc9-omap] i2c-omap: timeouts begone

[Woodruff, Richard]

> At least we can say the problem seems to be related to pm. Maybe after
> context restore we should wait until the clock stabilizes or some
> register changes ??

Maybe.  An experiment would be to not shut the clock off in the idle routine.

Actually, scanning i2c_init shows what looks to be a problem.

 235 static int omap_i2c_init(struct omap_i2c_dev *dev)
 236 {
 237         u16 psc = 0, scll = 0, sclh = 0;
 238         u16 fsscll = 0, fssclh = 0, hsscll = 0, hssclh = 0;
 239         unsigned long fclk_rate = 12000000;
 240         unsigned long timeout;
 241         unsigned long internal_clk = 0;
 242
 243         if (!dev->rev1) {
 244                 omap_i2c_write_reg(dev, OMAP_I2C_SYSC_REG, OMAP_I2C_SYSC_SRST);

None of the module local OCP registers are being setup properly.  A write of a 0x2 kills other settings.  If after this operation the SSYC reg will say:
        -Forced Idle
        -Locally gate I+F clock on ocp-segment idle request
        -wake up disabled

If it is left this way what can happen is when L4/L3 clock stop partial idle is broadcast, this module will ack and gate its clocks.  This will result in you dropping data. Or if the data was sent ok, but clock stop happens, you won't be able to wake the system properly as you've cleared the local wakeup generation.  The result will be a timeout.

On OMAP2 I2C wasn't hooked properly into PRCM for handshake so it needed a workaround.  The same isn't true for OMAP3.  Treating the two as if they are the same with respect to power is false.

Regards,
Richard W.

RE: [PATCH 2.6.27-rc9-omap] i2c-omap: timeouts begone

[Paul Walmsley]

Hi Richard,

trying to fix this problem and have a few questions.

On Wed, 8 Oct 2008, Woodruff, Richard wrote:

> None of the module local OCP registers are being setup properly.  A 
> write of a 0x2 kills other settings.  If after this operation the SSYC 
> reg will say:
>         -Forced Idle
>         -Locally gate I+F clock on ocp-segment idle request
>         -wake up disabled
> 
> If it is left this way what can happen is when L4/L3 clock stop partial 
> idle is broadcast, this module will ack and gate its clocks.  This will 
> result in you dropping data. Or if the data was sent ok, but clock stop 
> happens, you won't be able to wake the system properly as you've cleared 
> the local wakeup generation.  The result will be a timeout.

Okay, so for OMAP3, the workarounds in the omapzoom tree to change the 
SYSC.CLOCKACTIVITY bits when the clocks are enabled and disabled are not 
necessary?

It sounds like the only thing that is needed on OMAP3 is to make sure that 
the SYSCONFIG register is set properly after a software reset? 

> On OMAP2 I2C wasn't hooked properly into PRCM for handshake so it needed 
> a workaround.  The same isn't true for OMAP3.  Treating the two as if 
> they are the same with respect to power is false.

Could you explain further about which workaround this is?  OMAP2 I2C does 
not appear to have any SYSC bits exposed other than SOFTRESET?

- Paul

RE: [PATCH 2.6.27-rc9-omap] i2c-omap: timeouts begone

[Woodruff, Richard]

> Actually, scanning i2c_init shows what looks to be a problem.
>
>  235 static int omap_i2c_init(struct omap_i2c_dev *dev)
>  236 {
>  237         u16 psc = 0, scll = 0, sclh = 0;
>  238         u16 fsscll = 0, fssclh = 0, hsscll = 0, hssclh = 0;
>  239         unsigned long fclk_rate = 12000000;
>  240         unsigned long timeout;
>  241         unsigned long internal_clk = 0;
>  242
>  243         if (!dev->rev1) {
>  244                 omap_i2c_write_reg(dev, OMAP_I2C_SYSC_REG,
> OMAP_I2C_SYSC_SRST);
>
> None of the module local OCP registers are being setup properly.  A
> write of a 0x2 kills other settings.  If after this operation the SSYC
> reg will say:
>       -Forced Idle
>       -Locally gate I+F clock on ocp-segment idle request
>       -wake up disabled

BTW, I see these settings are correct in Zoom tree in clock functions. http://git.omapzoom.org/?p=omapkernel;a=blob;f=drivers/i2c/busses/i2c-omap.c;hb=d0b4bad4926f9a147a73498f7a62a0ae1cf6f83a

Regards,
Richard W.

Re: [PATCH 2.6.27-rc9-omap] i2c-omap: timeouts begone

[David Brownell]

On Wednesday 08 October 2008, Woodruff, Richard wrote:
> BTW, I see these settings are correct in Zoom tree in clock functions.

Someone working with that Zoom tree might consider putting
together a patch.  ;)

Meanwhile, I'll stick with my simple one.

- Dave