[Letux-kernel] FYI: backlight pwm issues

Lukas Maerdian lukas at goldelico.com
Sat May 28 19:20:09 CEST 2016


Hi Nikolaus,

I have now rebased the Android branch to letux-4.6, too. And the
backlight driver is working as expected, now!

My broken version was based upon letux-base (@4.6-rc7), so probably
there is some change regarding the backlight, which is merged into the
letux-<RELEASE> branches, but is not part of letux-base.

So Replicant is booting with 4.6 (incl. display, USB/ADB, serial). Also,
I made the BMA180 accel work, without the need of my hack in the
bma150.c module, by disabling the corresponding IRQ in the DT.

Best,
  Lukas

Am 22.05.2016 um 20:28 schrieb H. Nikolaus Schaller:
> Hi Lukas,
> I have rebased and built Letux-4.6. And backlight works for me (using Debian/LXDE).
> 
> BR,
> Nikolaus
> 
>> Am 21.05.2016 um 23:18 schrieb H. Nikolaus Schaller <hns at goldelico.com>:
>>
>> Hi,
>>
>>> Am 21.05.2016 um 15:30 schrieb Lukas Maerdian <lukas at goldelico.com>:
>>>
>>> Hi!
>>>
>>> are those pwm/backlight issues still valid for 4.6-rc7?
>>
>> Well, backlight did work since rc2 quite good - but not optimal. 100% level is not
>> the same as permanently enabling the gpio. The reason appears to be that the
>> backlight converter has a dead time of ca. 1.5ms after even a very short turn-off
>> impulse. I.e. if we run backlight with 500hz (2ms) 100% level is approx. 50% of
>> the maximum current.
>>
>>> I rebased the work/lukas/android branch to letux-base (4.6-rc7) today
>>> and now have the problem that the screen is turned off completely...
>>
>> Oops. That should not be.
>>
>>>
>>> I think that the pwm/backlight drivers are the culprit, as
>>> /sys/class/backlight/ is empty. The modules (pwm_bl and
>>> pwm_omap_dmtimer) are loaded, but interestingly pwm_omap_dmtimer is not
>>> used by any module (whereas it should be used by pwm_bl...):
>>>
>>> pwm_bl 3930 0 - Live 0x00000000
>>> pwm_omap_dmtimer 3597 0 - Live 0x00000000
>>>
>>> Also I was not able to activate the BL via its GPIO. This command
>>> returns -1 and the 'value' file is still set to 0:
>>>
>>> root at android:/ #  echo 1 > /sys/class/gpio/gpio57/value
>>>
>>> Are there some recent changes to the backlight drivers I need to know
>>> of?
>>
>> I think there was a patch included in 4.6-rc1 or rc2 but nothing else. I only
>> changed the ./bl script for the last -rc.
>>
>>> Or do you have any other idea of what could be the problem here?
>>
>> Not yet... I plan to upgrade to 4.6.0 tomorrow and do some more testing
>> than usual.
>>
>> BR,
>> Nikolaus
>>
>>
>>>
>>> BR,
>>> Lukas
>>>
>>>
>>> Full lsmod:
>>>
>>> root at android:/ # lsmod
>>>
>>> rtc_twl 4734 0 - Live 0x00000000
>>> gpio_twl4030 4058 0 - Live 0x00000000
>>> extcon_gpio 2627 0 - Live 0x00000000
>>> bma150 5498 0 - Live 0x00000000
>>> lis3lv02d_i2c 3042 0 - Live 0x00000000
>>> lis3lv02d 13075 1 lis3lv02d_i2c, Live 0x00000000
>>> input_polldev 3473 2 bma150,lis3lv02d, Live 0x00000000
>>> hmc5843_i2c 2566 0 - Live 0x00000000
>>> hmc5843_core 5415 1 hmc5843_i2c, Live 0x00000000
>>> itg3200 3907 1 - Live 0x00000000
>>> ehci_omap 2895 0 - Live 0x00000000
>>> libertas 96291 0 - Live 0x00000000
>>> cfg80211 500482 1 libertas, Live 0x00000000
>>> leds_tca6507 5318 0 - Live 0x00000000
>>> hci_uart 13298 0 - Live 0x00000000
>>> bluetooth 317593 1 hci_uart, Live 0x00000000
>>> iptable_nat 1494 1 - Live 0x00000000
>>> nf_conntrack_ipv4 12429 1 - Live 0x00000000
>>> nf_defrag_ipv4 1290 1 nf_conntrack_ipv4, Live 0x00000000
>>> nf_nat_ipv4 4483 1 iptable_nat, Live 0x00000000
>>> nf_nat 12743 1 nf_nat_ipv4, Live 0x00000000
>>> nf_conntrack 101882 3 nf_conntrack_ipv4,nf_nat_ipv4,nf_nat, Live 0x00000000
>>> twl4030_vibra 2340 0 - Live 0x00000000
>>> g_ffs 2843 1 - Live 0x00000000
>>> ip6table_mangle 1543 1 - Live 0x00000000
>>> omap2430 6795 0 - Live 0x00000000
>>> iptable_mangle 1412 1 - Live 0x00000000
>>> twl4030_pwrbutton 1950 0 - Live 0x00000000
>>> bq27xxx_battery 6876 0 - Live 0x00000000
>>> ip6table_raw 1214 1 - Live 0x00000000
>>> w1_bq27000 1151 0 - Live 0x00000000
>>> iptable_raw 1275 1 - Live 0x00000000
>>> omap_hdq 5338 0 - Live 0x00000000
>>> twl4030_charger 8059 0 - Live 0x00000000
>>> phy_twl4030_usb 7239 3 - Live 0x00000000
>>> musb_hdrc 61424 2 omap2430,phy_twl4030_usb, Live 0x00000000
>>> tsc2007 4222 0 - Live 0x00000000
>>> pwm_bl 3930 0 - Live 0x00000000
>>> pwm_omap_dmtimer 3597 0 - Live 0x00000000
>>> snd_soc_omap_mcbsp 15408 2 - Live 0x00000000
>>> snd_soc_omap 2743 1 snd_soc_omap_mcbsp, Live 0x00000000
>>> snd_pcm_dmaengine 3612 1 snd_soc_omap, Live 0x00000000
>>> snd_soc_omap_twl4030 6752 0 - Live 0x00000000
>>> snd_soc_simple_card 5969 0 - Live 0x00000000
>>> ip6table_filter 1328 1 - Live 0x00000000
>>> snd_soc_twl4030 41381 1 - Live 0x00000000
>>> ip6_tables 10384 3 ip6table_mangle,ip6table_raw,ip6table_filter, Live
>>> 0x00000000
>>> ipv6 365928 13 ip6table_mangle,[permanent], Live 0x00000000
>>> omapdrm 55793 2 - Live 0x00000000
>>> drm_kms_helper 89714 1 omapdrm, Live 0x00000000
>>> cfbcopyarea 2803 1 drm_kms_helper, Live 0x00000000
>>> sysimgblt 1973 1 drm_kms_helper, Live 0x00000000
>>> sysfillrect 3135 1 drm_kms_helper, Live 0x00000000
>>> iptable_filter 1388 1 - Live 0x00000000
>>> cfbimgblt 2037 1 drm_kms_helper, Live 0x00000000
>>> syscopyarea 2867 1 drm_kms_helper, Live 0x00000000
>>> cfbfillrect 3199 1 drm_kms_helper, Live 0x00000000
>>> fb_sys_fops 1461 1 drm_kms_helper, Live 0x00000000
>>> drm 248029 3 omapdrm,drm_kms_helper, Live 0x00000000
>>> ip_tables 10189 4 iptable_nat,iptable_mangle,iptable_raw,iptable_filter,
>>> Live 0x00000000
>>> x_tables 11636 8
>>> ip6table_mangle,iptable_mangle,ip6table_raw,iptable_raw,ip6table_filter,ip6_tables,iptable_filter,ip_tables,
>>> Live 0x00000000
>>> panel_tpo_td028ttec1 4487 1 - Live 0x00000000
>>> omapdss 184617 3 omapdrm,panel_tpo_td028ttec1, Live 0x00000000
>>> usb_f_fs 20546 3 g_ffs, Live 0x00000000
>>> libcomposite 33022 2 g_ffs,usb_f_fs, Live 0x00000000
>>> configfs 22622 3 usb_f_fs,libcomposite, Live 0x00000000
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>>
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