RE: [PWM PATCH 1/5] API to consolidate PWM devices behind a common user and kernel interface

From: H Hartley Sweeten
Date: Wed Feb 03 2010 - 20:39:34 EST

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On Tuesday, February 02, 2010 12:15 AM, Bill Gatliff wrote:
> Signed-off-by: Bill Gatliff <bgat@xxxxxxxxxxxxxxx>
> ---
> Documentation/pwm.txt | 260 +++++++++++++++++++
> drivers/pwm/pwm.c | 633 +++++++++++++++++++++++++++++++++++++++++++++++
> include/linux/pwm.h | 31 ---
> include/linux/pwm/pwm.h | 170 +++++++++++++
> 4 files changed, 1063 insertions(+), 31 deletions(-)
> create mode 100644 Documentation/pwm.txt
> create mode 100644 drivers/pwm/pwm.c
> delete mode 100644 include/linux/pwm.h
> create mode 100644 include/linux/pwm/pwm.h

[snip]

> diff --git a/drivers/pwm/pwm.c b/drivers/pwm/pwm.c
> new file mode 100644
> index 0000000..f369384
> --- /dev/null
> +++ b/drivers/pwm/pwm.c

[snip]

> +int pwm_register(struct pwm_device *pwm)
> +{
> + struct pwm_channel *p;
> + int wchan;
> + int ret;
> +
> + spin_lock_init(&pwm->list_lock);
> +
> + p = kcalloc(pwm->nchan, sizeof(*p), GFP_KERNEL);
> + if (!p)
> + return -ENOMEM;
> +
> + for (wchan = 0; wchan < pwm->nchan; wchan++) {
> + spin_lock_init(&p[wchan].lock);
> + init_completion(&p[wchan].complete);
> + p[wchan].chan = wchan;
> + p[wchan].pwm = pwm;
> + }
> +
> + pwm->channels = p;
> +
> + mutex_lock(&device_list_mutex);
> +
> + list_add_tail(&pwm->list, &pwm_device_list);
> + ret = __pwm_create_sysfs(pwm);
> + if (ret) {
> + mutex_unlock(&device_list_mutex);
> + goto err_create_sysfs;
> + }
> +
> + mutex_unlock(&device_list_mutex);
> +
> + dev_info(pwm->dev, "%d channel%s\n", pwm->nchan,
> + pwm->nchan > 1 ? "s" : "");
> + return 0;
> +
> +err_create_sysfs:
> + kfree(p);
> +
> + return ret;
> +}
> +EXPORT_SYMBOL(pwm_register);

Bill,

I'm trying to test your latest pwm patches using the ep93xx pwm driver
I wrote based on your previous patches. I'm getting an Oops when booting
this that is hanging my system. I put in the printascii hack to see
what's going on and got this:

<1>Unable to handle kernel NULL pointer dereference at virtual address 00000044
<1>pgd = c0004000
<1>[00000044] *pgd=00000000
<0>Internal error: Oops: 5 [#1] PREEMPT
<0>last sysfs file:
<d>Modules linked in:
CPU: 0 Not tainted (2.6.32.7 #5)
PC is at dev_driver_string+0x0/0x38
LR is at pwm_register+0x17c/0x1e8
pc : [<c01b1b10>] lr : [<c0187dfc>] psr: 60000013
sp : c581bee0 ip : c036efa5 fp : 00000000
r10: c4511e60 r9 : 00000000 r8 : 00000000
r7 : c036ef6c r6 : 00000050 r5 : c44c9b20 r4 : 00000001
r3 : 00000001 r2 : 00000001 r1 : 00000000 r0 : 00000000
Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment kernel
Control: c000717f Table: c0004000 DAC: 00000017
<0>Process swapper (pid: 1, stack limit = 0xc581a270)
<0>Stack: (0xc581bee0 to 0xc581c000)
<0>bee0: c036ef6c c58449a0 00000000 c44c9b20 00000000 c44c9b20 00000000 c03bece8
<0>bf00: c58839c0 c03bece0 00000000 c0016784 00000000 00000000 c03bece8 c03bece8
<0>bf20: c03d105c c03d105c c03d4c40 c01b5e70 c03d105c c01b4f08 c0054498 c03bece8
<0>bf40: c03bed1c c03d105c c581bf60 c01b5038 00000000 c01b4fdc c03d105c c01b473c
<0>bf60: c58034d8 c5852dd0 c03d4c40 c00211c4 c03d105c c03d105c c4511ec0 c01b4028
<0>bf80: c0351a5d c581bf90 c01756c4 c00211c4 c002133c c03d105c c001666c 00000001
<0>bfa0: 00000000 c01b533c c00211c4 c002133c 00000000 c001666c 00000001 c00273a8
<0>bfc0: 00000000 00000078 c03c2aa0 00000000 c00211c4 c002133c 00000000 00000000
<0>bfe0: 00000000 c0008588 00000000 00000000 00000000 c00289d4 33cc33cc 33cc33cc
[<c01b1b10>] (dev_driver_string+0x0/0x38) from [<c0187dfc>] (pwm_register+0x17c/0x1e8)
[<c0187dfc>] (pwm_register+0x17c/0x1e8) from [<c0016784>] (ep93xx_pwm_probe+0x10c/0x17c)
[<c0016784>] (ep93xx_pwm_probe+0x10c/0x17c) from [<c01b5e70>] (platform_drv_probe+0x1c/0x24)
[<c01b5e70>] (platform_drv_probe+0x1c/0x24) from [<c01b4f08>] (driver_probe_device+0xac/0x180)
[<c01b4f08>] (driver_probe_device+0xac/0x180) from [<c01b5038>] (__driver_attach+0x5c/0x7c)
[<c01b5038>] (__driver_attach+0x5c/0x7c) from [<c01b473c>] (bus_for_each_dev+0x50/0x90)
[<c01b473c>] (bus_for_each_dev+0x50/0x90) from [<c01b4028>] (bus_add_driver+0xa0/0x224)
[<c01b4028>] (bus_add_driver+0xa0/0x224) from [<c01b533c>] (driver_register+0xbc/0x14c)
[<c01b533c>] (driver_register+0xbc/0x14c) from [<c00273a8>] (do_one_initcall+0x60/0x1c0)
[<c00273a8>] (do_one_initcall+0x60/0x1c0) from [<c0008588>] (kernel_init+0x9c/0x114)
[<c0008588>] (kernel_init+0x9c/0x114) from [<c00289d4>] (kernel_thread_exit+0x0/0x8)
<0>Code: c03c5c28 000080d0 c03d49c8 c03d4958 (e5903044)
<4>---[ end trace da227214a82491b7 ]---
<0>Kernel panic - not syncing: Attempted to kill init!
[<c002c7dc>] (unwind_backtrace+0x0/0xdc) from [<c02d7050>] (panic+0x3c/0x128)
[<c02d7050>] (panic+0x3c/0x128) from [<c003ee2c>] (do_exit+0x60/0x608)
[<c003ee2c>] (do_exit+0x60/0x608) from [<c002b5f8>] (die+0x178/0x19c)
[<c002b5f8>] (die+0x178/0x19c) from [<c002db1c>] (__do_kernel_fault+0x68/0x80)
[<c002db1c>] (__do_kernel_fault+0x68/0x80) from [<c002dcf8>] (do_page_fault+0x1c4/0x1dc)
[<c002dcf8>] (do_page_fault+0x1c4/0x1dc) from [<c00272e8>] (do_DataAbort+0x34/0x94)
[<c00272e8>] (do_DataAbort+0x34/0x94) from [<c0027ae0>] (__dabt_svc+0x40/0x60)
Exception stack(0xc581be98 to 0xc581bee0)
be80: 00000000 00000000
bea0: 00000001 00000001 00000001 c44c9b20 00000050 c036ef6c 00000000 00000000
bec0: c4511e60 00000000 c036efa5 c581bee0 c0187dfc c01b1b10 60000013 ffffffff
[<c0027ae0>] (__dabt_svc+0x40/0x60) from [<c01b1b10>] (dev_driver_string+0x0/0x38)
[<c01b1b10>] (dev_driver_string+0x0/0x38) from [<c0187dfc>] (pwm_register+0x17c/0x1e8)
[<c0187dfc>] (pwm_register+0x17c/0x1e8) from [<c0016784>] (ep93xx_pwm_probe+0x10c/0x17c)
[<c0016784>] (ep93xx_pwm_probe+0x10c/0x17c) from [<c01b5e70>] (platform_drv_probe+0x1c/0x24)
[<c01b5e70>] (platform_drv_probe+0x1c/0x24) from [<c01b4f08>] (driver_probe_device+0xac/0x180)
[<c01b4f08>] (driver_probe_device+0xac/0x180) from [<c01b5038>] (__driver_attach+0x5c/0x7c)
[<c01b5038>] (__driver_attach+0x5c/0x7c) from [<c01b473c>] (bus_for_each_dev+0x50/0x90)
[<c01b473c>] (bus_for_each_dev+0x50/0x90) from [<c01b4028>] (bus_add_driver+0xa0/0x224)
[<c01b4028>] (bus_add_driver+0xa0/0x224) from [<c01b533c>] (driver_register+0xbc/0x14c)
[<c01b533c>] (driver_register+0xbc/0x14c) from [<c00273a8>] (do_one_initcall+0x60/0x1c0)
[<c00273a8>] (do_one_initcall+0x60/0x1c0) from [<c0008588>] (kernel_init+0x9c/0x114)
[<c0008588>] (kernel_init+0x9c/0x114) from [<c00289d4>] (kernel_thread_exit+0x0/0x8)

Your older patch just used printk's to output the messages. I think the
Oops is being caused by the dev_<level>(pwm->dev, ...). Where is pwm->dev
being setup?

Regards,
Hartley

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In reply to: Bill Gatliff: "Re: [PWM PATCH 1/5] API to consolidate PWM devices behind a commonuser and kernel interface"
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