[Letux-kernel] FYI: backlight pwm issues

[H. Nikolaus Schaller]

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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