[Letux-kernel] weird problem with pwm_bl on omap3

H. Nikolaus Schaller hns at goldelico.com
Mon Jun 11 17:00:47 CEST 2018


Hi,
now here is a similar report from the Pyra...

>> And the strcmp(NULL, "backlight_pins_pinmux") occurred
>> first in 4.17-rc1. But it might just be a more visible
>> symptom and the bug may be older.
> 
> Latest boot log:
> 
> [    8.381225] pwm_backlight_probe
> [    8.384613] pwm-backlight backlight: backlight supply power not found, using dummy regulator
> [    8.503112] pwm_backlight_probe probe error -517
> [    8.517517] wwan_on_off_init: wwan_on_off_init
> [    8.549804] (NULL device *): hwmon: 'gta04-battery' is not a valid name attribute, please fix
> [    8.565521] pps_core: LinuxPPS API ver. 1 registered
> [    8.570709] pps_core: Software ver. 5.3.6 - Copyright 2005-2007 Rodolfo Giometti <giometti at linux.it>
> [    8.604522] pinctrl_get_group_selector: strcmp: (null) backlight_pins_pinmux

[    6.130045] pinctrl_get_group_selector: strcmp: (null) pinmux_backlight_pins

> [    8.612243] iio_charge:-749
> [    8.622192] Unable to handle kernel NULL pointer dereference at virtual address 00000000
> [    8.641662] pgd = (ptrval)
> [    8.644897] [00000000] *pgd=00000000
> [    8.652252] Internal error: Oops: 17 [#1] PREEMPT SMP ARM
> [    8.657897] Modules linked in: pps_core(+) encoder_opa362(+) wwan_on_off(+) snd_soc_gtm601 connector_analog_tv pwm_omap_dmtimer omapdss_base generic_adc_battery pwm_bl wlcore_sdio bmp280_spi bq27xxx_battery_hdq bq27xxx_battery omap_hdq omap2430 ov9655 v4l2_fwnode v4l2_common snd_soc_omap_mcbsp snd_soc_omap snd_pcm_dmaengine bmp280_i2c bmp280 videodev bmc150_magn_i2c tsc2007 bmc150_accel_i2c bmc150_magn at24 bmc150_accel_core leds_tca6507 industrialio_triggered_buffer media kfifo_buf phy_twl4030_usb gpio_twl4030 musb_hdrc twl4030_pwrbutton twl4030_vibra snd_soc_twl4030 twl4030_madc twl4030_charger industrialio gnss_w2sg0004 w2cbw003_bluetooth gnss ehci_omap
> [    8.718811] CPU: 0 PID: 917 Comm: kworker/0:2 Not tainted 4.17.0-rc3-letux+ #2356
> [    8.726623] Hardware name: Generic OMAP36xx (Flattened Device Tree)
> [    8.733184] Workqueue: events deferred_probe_work_func
> [    8.738555] PC is at strcmp+0x0/0x34
> [    8.742309] LR is at pinctrl_get_group_selector+0x6c/0xa8
> [    8.747955] pc : [<c071a6e0>]    lr : [<c0436880>]    psr: 60000013
> [    8.754516] sp : ee6a9e08  ip : 00000000  fp : 0000001a
> [    8.759979] r10: 00000017  r9 : 0000001a  r8 : c075b144
> [    8.765472] r7 : 00000000  r6 : ee3e4d80  r5 : ef7c4a20  r4 : 00000017
> [    8.772308] r3 : 00000000  r2 : 00000002  r1 : ef7c4a20  r0 : 00000000
> [    8.779144] Flags: nZCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment none
> [    8.786621] Control: 10c5387d  Table: ad02c019  DAC: 00000051
> [    8.792633] Process kworker/0:2 (pid: 917, stack limit = 0x(ptrval))
> [    8.799285] Stack: (0xee6a9e08 to 0xee6aa000)
> [    8.803833] 9e00:                   ee6a9e2c ee3e4d80 ef7c4a20 00000000 ed0cce10 00000000
> [    8.812408] 9e20: ed071140 c0437848 ed0d8210 00000001 00000002 ed265d00 ed071180 ed0711c0
> [    8.820953] 9e40: ed0cce10 00000000 00000000 ed071140 00000000 c0436080 00000014 ee26e4c0
> [    8.829498] 9e60: c0b5a0b0 c0890054 ee2b8010 00000000 ed265d50 ee2b8010 c0bccf44 fffffdfb
> [    8.838073] 9e80: bf1ac014 00000029 c0b95730 c0436248 00000000 ee2b8010 ed071290 c04c8cac
> [    8.846618] 9ea0: ee2b8010 00000000 c0bccf48 c04acd3c 00000000 ee6a9ee8 c04ad048 ee2b8044
> [    8.855194] 9ec0: ef7baf00 c0b03d00 00000000 c04ab59c ee020e6c ed146b38 ee2b8010 c0b64550
> [    8.863769] 9ee0: 00000001 c04acbbc ee2b8010 00000001 00000000 ee2b8010 c0b64550 ee2b8010
> [    8.872314] 9f00: c0b9f060 c04ac178 ee2b8010 c0b6433c c0b64358 c04ac688 c04ac59c ee6caa80
> [    8.880859] 9f20: c0b64370 ef7b7c40 00000000 ef7baf00 c0b03d00 c01444f0 ee6caa80 c0b64370
> [    8.889404] 9f40: ffff8e2b ee6caa80 ef7b7c40 ef7b7c40 ee6a8000 ef7b7c58 c0b03d00 ee6caa98
> [    8.897979] 9f60: 00000008 c0144cc4 ee223280 ee374180 ee374240 00000000 ee6caa80 c0144a04
> [    8.906555] 9f80: ee0bbef0 ee37419c 00000000 c0148cbc ee374240 c0148b88 00000000 00000000
> [    8.915100] 9fa0: 00000000 00000000 00000000 c01010e8 00000000 00000000 00000000 00000000
> [    8.923645] 9fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> [    8.932220] 9fe0: 00000000 00000000 00000000 00000000 00000013 00000000 00000000 00000000
> [    8.940795] [<c071a6e0>] (strcmp) from [<c0436880>] (pinctrl_get_group_selector+0x6c/0xa8)
> [    8.949462] [<c0436880>] (pinctrl_get_group_selector) from [<c0437848>] (pinmux_map_to_setting+0x158/0x1a0)
> [    8.959655] [<c0437848>] (pinmux_map_to_setting) from [<c0436080>] (create_pinctrl+0x1f0/0x2f8)
> [    8.968749] [<c0436080>] (create_pinctrl) from [<c0436248>] (devm_pinctrl_get+0x2c/0x6c)
> [    8.977233] [<c0436248>] (devm_pinctrl_get) from [<c04c8cac>] (pinctrl_bind_pins+0x3c/0x138)
> [    8.986083] [<c04c8cac>] (pinctrl_bind_pins) from [<c04acd3c>] (driver_probe_device+0xe8/0x318)
> [    8.995178] [<c04acd3c>] (driver_probe_device) from [<c04ab59c>] (bus_for_each_drv+0x84/0x94)
> [    9.004119] [<c04ab59c>] (bus_for_each_drv) from [<c04acbbc>] (__device_attach+0x88/0xfc)
> [    9.012695] [<c04acbbc>] (__device_attach) from [<c04ac178>] (bus_probe_device+0x28/0x80)
> [    9.021240] [<c04ac178>] (bus_probe_device) from [<c04ac688>] (deferred_probe_work_func+0xec/0x120)
> [    9.030731] [<c04ac688>] (deferred_probe_work_func) from [<c01444f0>] (process_one_work+0x244/0x464)
> [    9.040313] [<c01444f0>] (process_one_work) from [<c0144cc4>] (worker_thread+0x2c0/0x3ec)
> [    9.048889] [<c0144cc4>] (worker_thread) from [<c0148cbc>] (kthread+0x134/0x150)
> [    9.056610] [<c0148cbc>] (kthread) from [<c01010e8>] (ret_from_fork+0x14/0x2c)
> [    9.064178] Exception stack(0xee6a9fb0 to 0xee6a9ff8)
> [    9.069458] 9fa0:                                     00000000 00000000 00000000 00000000
> [    9.078002] 9fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> [    9.086578] 9fe0: 00000000 00000000 00000000 00000000 00000013 00000000
> [    9.093505] Code: e3520000 e5e32001 1afffffb e12fff1e (e4d03001)
> [    9.563262] ---[ end trace 27838669a01b24aa ]---
> [   11.037506] cfg80211: Loading compiled-in X.509 certificates for regulatory database
> [   11.078430] cfg80211: Loaded X.509 cert 'sforshee: 00b28ddf47aef9cea7'
> [   11.100646] platform regulatory.0: Direct firmware load for regulatory.db failed with error -2
> [   11.119567] cfg80211: failed to load regulatory.db
> [   22.575958] random: crng init done

More complete log:

[    6.048157] ehci-omap: OMAP-EHCI Host Controller driver
[    6.076090] emif_probe: error getting device data
[    6.082016] emif_probe: error getting device data
[    6.100762] pwm-backlight backlight: backlight supply power not found, using dummy regulator
[    6.110719] (NULL device *): hwmon: 'pyra-battery' is not a valid name attribute, please fix
[    6.123389] platform backlight: Retrying from deferred list
[    6.130045] pinctrl_get_group_selector: strcmp: (null) pinmux_backlight_pins
[    6.137625] ehci-omap 4a064c00.ehci: EHCI Host Controller
[    6.143363] Unable to handle kernel NULL pointer dereference at virtual address 00000000
[    6.152323] ehci-omap 4a064c00.ehci: new USB bus registered, assigned bus number 1
[    6.160407] pgd = (ptrval)
[    6.163285] omapdss: unknown parameter 'def_disp' ignored
[    6.169043] [00000000] *pgd=00000000
[    6.173665] iio_charge:0
[    6.176535] Internal error: Oops: 17 [#1] PREEMPT SMP ARM
[    6.182193] Modules linked in: connector_hdmi(+) encoder_tpd12s015(+) omapdss(+) pwm_omap_dmtimer omapdss_base generic_adc_battery pwm_bl(+) cec ehci_omap(+) wlcore_sdio dwc3_omap bmp280_spi snd_soc_ts3a227e leds_is31fl319x crtouch_mt tsc2007 bq27xxx_battery_i2c(+) bq27xxx_battery bq2429x_charger ina2xx gpio_twl6040 twl6040_vibra bmc150_accel_i2c bmc150_magn_i2c bmc150_accel_core bmc150_magn bno055 bmp280_i2c palmas_pwrbutton industrialio_triggered_buffer bmp280 kfifo_buf palmas_gpadc usb3503 w2cbw003_bluetooth industrialio as5013 tca8418_keypad snd_soc_omap_mcbsp snd_soc_omap_mcpdm snd_soc_omap snd_pcm_dmaengine
[    6.239236] CPU: 0 PID: 1331 Comm: kworker/0:5 Tainted: G        W         4.17.0-letux+ #2410
[    6.248273] Hardware name: Generic OMAP5 (Flattened Device Tree)
[    6.254577] Workqueue: events deferred_probe_work_func
[    6.259962] PC is at strcmp+0x0/0x34
[    6.263718] LR is at pinctrl_get_group_selector+0x6c/0xa8
[    6.269378] pc : [<c0758d60>]    lr : [<c042d924>]    psr: 600e0013
[    6.275945] sp : ecd0be10  ip : 00000000  fp : 00000019
[    6.281418] r10: 00000017  r9 : 00000019  r8 : c0799f54
[    6.286893] r7 : 00000000  r6 : edd99c00  r5 : eefefa94  r4 : 00000017
[    6.293738] r3 : 600e0013  r2 : 00000002  r1 : eefefa94  r0 : 00000000
[    6.300573] Flags: nZCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment none
[    6.308052] Control: 10c5387d  Table: acb9006a  DAC: 00000051
[    6.314072] Process kworker/0:5 (pid: 1331, stack limit = 0x(ptrval))
[    6.320826] Stack: (0xecd0be10 to 0xecd0c000)
[    6.325392] be00:                                     ecd0be34 edd99c00 eefefa94 00000000
[    6.333966] be20: eca59090 00000000 ecdd6800 c042e8ec eccedf50 00000001 00000002 ecdd6a80
[    6.342538] be40: ecdd6840 ecdd6880 eca59090 00000000 00000000 ecdd6800 00000000 c042d124
[    6.351106] be60: 0000003a eda4a940 c0b59e30 c08e9e3c c042d258 00000000 ecdd6ad0 eda49210
[    6.359683] be80: c0bd1df0 fffffdfb bf1cc014 0000003a c0b98f70 c042d2ec 00000000 eda49210
[    6.368259] bea0: ecdd6b10 c04f2d30 eda49210 00000000 c0bd1df4 c04d3d4c 00000000 ecd0bef0
[    6.376836] bec0: c04d4058 eda49244 c0b664c4 c0b02d00 00000000 c04d259c ed8dde6c eca592b8
[    6.385412] bee0: eda49210 c0b666c8 00000001 c04d3bcc eda49210 00000001 00000002 eda49210
[    6.393990] bf00: c0b666c8 eda49210 00000000 c04d3178 eda49210 c0b664a8 eefcfc80 c04d3694
[    6.402566] bf20: ecd2ef00 c0b664dc eefcfc80 00000000 eefd2f00 c014874c ecd2ef00 c0b664dc
[    6.411137] bf40: ffff8d33 ecd2ef00 eefcfc80 eefcfc80 ecd0a000 eefcfc98 c0b02d00 ecd2ef18
[    6.419708] bf60: 00000008 c0148f20 00000000 ecd34940 ecbb24c0 00000000 ecd2ef00 c0148c60
[    6.428281] bf80: eda5fef0 ecd3495c 00000000 c014cef4 ecbb24c0 c014cdc0 00000000 00000000
[    6.436853] bfa0: 00000000 00000000 00000000 c01010e8 00000000 00000000 00000000 00000000
[    6.445422] bfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
[    6.453997] bfe0: 00000000 00000000 00000000 00000000 00000013 00000000 00000000 00000000
[    6.462577] [<c0758d60>] (strcmp) from [<c042d924>] (pinctrl_get_group_selector+0x6c/0xa8)
[    6.471246] [<c042d924>] (pinctrl_get_group_selector) from [<c042e8ec>] (pinmux_map_to_setting+0x158/0x1a0)
[    6.481465] [<c042e8ec>] (pinmux_map_to_setting) from [<c042d124>] (create_pinctrl+0x1f0/0x2f8)
[    6.490591] [<c042d124>] (create_pinctrl) from [<c042d2ec>] (devm_pinctrl_get+0x2c/0x6c)
[    6.499085] [<c042d2ec>] (devm_pinctrl_get) from [<c04f2d30>] (pinctrl_bind_pins+0x3c/0x138)
[    6.507939] [<c04f2d30>] (pinctrl_bind_pins) from [<c04d3d4c>] (driver_probe_device+0xe8/0x318)
[    6.517069] [<c04d3d4c>] (driver_probe_device) from [<c04d259c>] (bus_for_each_drv+0x84/0x94)
[    6.526020] [<c04d259c>] (bus_for_each_drv) from [<c04d3bcc>] (__device_attach+0x88/0xfc)
[    6.534595] [<c04d3bcc>] (__device_attach) from [<c04d3178>] (bus_probe_device+0x28/0x80)
[    6.543169] [<c04d3178>] (bus_probe_device) from [<c04d3694>] (deferred_probe_work_func+0xf8/0x130)
[    6.552663] [<c04d3694>] (deferred_probe_work_func) from [<c014874c>] (process_one_work+0x244/0x464)
[    6.562238] [<c014874c>] (process_one_work) from [<c0148f20>] (worker_thread+0x2c0/0x3ec)
[    6.570819] [<c0148f20>] (worker_thread) from [<c014cef4>] (kthread+0x134/0x150)
[    6.578585] [<c014cef4>] (kthread) from [<c01010e8>] (ret_from_fork+0x14/0x2c)
[    6.586160] Exception stack(0xecd0bfb0 to 0xecd0bff8)
[    6.591448] bfa0:                                     00000000 00000000 00000000 00000000
[    6.600010] bfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
[    6.608576] bfe0: 00000000 00000000 00000000 00000000 00000013 00000000
[    6.615499] Code: e3520000 e5e32001 1afffffb e12fff1e (e4d03001)
[    6.623205] bq27xxx-battery 1-0055: cfgupdate 0, retries 8
[    6.626766] ---[ end trace 1e8ab5ac125bd84c ]---
[    6.629004] bq27xxx_battery_seal
[    6.637717] wwan_on_off_init: wwan_on_off_init
[    6.637730] ehci-omap 4a064c00.ehci: irq 146, io mem 0x4a064c00
[    6.684536] ehci-omap 4a064c00.ehci: USB 2.0 started, EHCI 1.00

iio_charge is also involved. Looks as if the gab driver and the pwm_bl drivers are
probed almost in parallel. On GTA04A5 and Pyra. Despite different SoC...

The problem is that there is a strcmp() in pinctrl_get_group_selector() which tries to
match "pinmux_backlight_pins":

> int pinctrl_get_group_selector(struct pinctrl_dev *pctldev,
> 			       const char *pin_group)
> {
> 	const struct pinctrl_ops *pctlops = pctldev->desc->pctlops;
> 	unsigned ngroups = pctlops->get_groups_count(pctldev);
> 	unsigned group_selector = 0;
> 
> 	while (group_selector < ngroups) {
> 		const char *gname = pctlops->get_group_name(pctldev,
> 							    group_selector);
> if(!gname || !pin_group) printk("%s: strcmp: %s %s\n", __func__, gname, pin_group);
> 		if (!strcmp(gname, pin_group)) {
> 			dev_dbg(pctldev->dev,
> 				"found group selector %u for %s\n",
> 				group_selector,
> 				pin_group);
> 			return group_selector;
> 		}
> 
> 		group_selector++;
> 	}
> 
> 	dev_err(pctldev->dev, "does not have pin group %s\n",
> 		pin_group);
> 
> 	return -EINVAL;
> }
> 

This means that gname == NULL.

The big question is: why?

Ah, I have some ideas:
1. find out what pctlops->get_group_name points to (seems to be a dynamic function pointer)
2. try to trace what it is doing - may be it points to a dummy function which returns NULL?

BR,
Nikolaus

PS: on next boot I got this:

[    8.441935] platform backlight: Retrying from deferred list
[    8.448597] pwm-backlight backlight: backlight supply power not found, using dummy regulator
[    8.457753] Unable to handle kernel NULL pointer dereference at virtual address 0000000b
[    8.466228] pgd = (ptrval)
[    8.469060] [0000000b] *pgd=fd09d835
[    8.472816] Internal error: Oops: 17 [#1] PREEMPT SMP ARM
[    8.478479] Modules linked in: pwm_omap_dmtimer(+) generic_adc_battery(+) emif(-) pwm_bl ehci_omap(+) wlcore_sdio dwc3_omap snd_soc_ts3a227e leds_is31fl319x tsc2007 crtouch_mt bmp280_spi bq2429x_charger bq27xxx_battery_i2c bq27xxx_battery ina2xx gpio_twl6040 as5013 twl6040_vibra tca8418_keypad bmc150_magn_i2c palmas_pwrbutton bmc150_accel_i2c bno055 bmc150_magn bmc150_accel_core bmp280_i2c palmas_gpadc industrialio_triggered_buffer bmp280 kfifo_buf industrialio w2cbw003_bluetooth usb3503 snd_soc_omap_mcpdm snd_soc_omap_mcbsp snd_soc_omap snd_pcm_dmaengine
[    8.530137] CPU: 1 PID: 1294 Comm: udevd Tainted: G        W         4.17.0-letux+ #2410
[    8.538610] Hardware name: Generic OMAP5 (Flattened Device Tree)
[    8.544906] PC is at ___cache_free+0x8/0x16c
[    8.549378] LR is at kfree+0xd0/0x11c
[    8.553210] pc : [<c023f460>]    lr : [<c023fcc4>]    psr: 600e0193
[    8.559771] sp : ecb55e18  ip : ef019000  fp : 00000000
[    8.565238] r10: 00000000  r9 : bf1f71b0  r8 : bf1f7180
[    8.570707] r7 : 00000000  r6 : 00000011  r5 : c01a4348  r4 : 200e0113
[    8.577550] r3 : ef819000  r2 : c01a4348  r1 : 00000011  r0 : 0000000b
[    8.584389] Flags: nZCv  IRQs off  FIQs on  Mode SVC_32  ISA ARM  Segment none
[    8.591953] Control: 10c5387d  Table: acb5806a  DAC: 00000051
[    8.597964] Process udevd (pid: 1294, stack limit = 0x(ptrval))
[    8.604164] Stack: (0xecb55e18 to 0xecb56000)
[    8.608730] 5e00:                                                       ece8c898 a00e0113
[    8.617299] 5e20: c074f634 ecc7e580 00000000 bf1f7180 bf1f71b0 200e0113 c01a4348 00000011
[    8.625872] 5e40: 00000000 bf1f7180 bf1f71b0 00000000 00000000 c023fcc4 bf1f7080 ffffffed
[    8.634436] 5e60: 00000002 c01a4348 c01c55a0 bf1f7080 ffffffed c01a72ac bf1f7080 ecd421c0
[    8.643005] 5e80: bf1f7080 ecb55f50 bf1f708c c01a5fa4 ffff8000 00007fff bf1f7080 c01a32d4
[    8.651573] 5ea0: 00000099 c076a678 f0b031f4 b6df89f8 00000000 00000003 ecb0a240 00004244
[    8.660140] 5ec0: 00000000 c024cf6c 00000003 00000000 00000000 00000000 00000000 00000000
[    8.668709] 5ee0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
[    8.677278] 5f00: 00000000 00000000 7fffffff 00000000 b6df89f8 00000006 0000017b c01011e4
[    8.685845] 5f20: ecb54000 00000000 000510b0 c01a6328 7fffffff 00000000 00000003 c021707c
[    8.694408] 5f40: 00000002 f0aff000 00004244 00000000 f0b00ad5 f0aff000 00004244 f0b02d44
[    8.702968] 5f60: f0b013f7 f0b01ed0 00004000 000042c0 00000000 00000000 00000000 00002024
[    8.711532] 5f80: 0000001e 0000001f 00000016 00000000 00000012 00000000 b6df97d4 00051f68
[    8.720100] 5fa0: e53e5c00 c0101000 b6df97d4 00051f68 00000006 b6df89f8 00000000 b6df931c
[    8.728675] 5fc0: b6df97d4 00051f68 e53e5c00 0000017b 00020000 00037f78 00050048 000510b0
[    8.737246] 5fe0: bec1dee0 bec1ded0 b6df2c4b b6efda42 600f0030 00000006 00000000 00000000
[    8.745824] [<c023f460>] (___cache_free) from [<c023fcc4>] (kfree+0xd0/0x11c)
[    8.753298] [<c023fcc4>] (kfree) from [<c01a4348>] (free_module+0xac/0x1f0)
[    8.760585] [<c01a4348>] (free_module) from [<c01a72ac>] (do_init_module+0x190/0x1d0)
[    8.768771] [<c01a72ac>] (do_init_module) from [<c01a5fa4>] (load_module+0xe04/0xfb0)
[    8.776964] [<c01a5fa4>] (load_module) from [<c01a6328>] (sys_finit_module+0x88/0x90)
[    8.785153] [<c01a6328>] (sys_finit_module) from [<c0101000>] (ret_fast_syscall+0x0/0x54)
[    8.793700] Exception stack(0xecb55fa8 to 0xecb55ff0)
[    8.798985] 5fa0:                   b6df97d4 00051f68 00000006 b6df89f8 00000000 b6df931c
[    8.807547] 5fc0: b6df97d4 00051f68 e53e5c00 0000017b 00020000 00037f78 00050048 000510b0
[    8.816104] 5fe0: bec1dee0 bec1ded0 b6df2c4b b6efda42
[    8.821391] Code: e3a00000 e12fff1e e92d4ff0 e24dd01c (e5904000)
[    8.827770] ---[ end trace 9dd0443b2512a841 ]---
[    8.832843] platform keyboard-backlight: Retrying from deferred list
[    8.839983] pwm-backlight keyboard-backlight: keyboard-backlight supply power not found, using dummy regulator
[    8.850936] iio_charge:0
[    8.853718] ehci-omap 4a064c00.ehci: EHCI Host Controller
[    8.860411] ehci-omap 4a064c00.ehci: new USB bus registered, assigned bus number 1

This is a hint that we have some kfree(NULL) as well... Again a hint at the error path
of pwm_bl or some dangling pointer.



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