[Letux-kernel] Kernel v5.1-rc1 (was: LetuxOS Kernel v5.0-rc1)

H. Nikolaus Schaller hns at goldelico.com
Thu Mar 21 07:12:31 CET 2019


> Am 21.03.2019 um 07:05 schrieb H. Nikolaus Schaller <hns at goldelico.com>:
> 
> HI,
> 
>> Am 20.03.2019 um 16:31 schrieb H. Nikolaus Schaller <hns at goldelico.com>:
>> 
>> Hi,
>> 
>>> Am 20.03.2019 um 08:30 schrieb H. Nikolaus Schaller <hns at goldelico.com>:
>>> 
>>> Hi,
>>> 
>>>> Am 20.03.2019 um 08:19 schrieb Andreas Kemnade <andreas at kemnade.info>:
>>>> 
>>>> Hi,
>>>> 
>>>> 
>>>> On Tue, 19 Mar 2019 13:30:17 +0100
>>>> "H. Nikolaus Schaller" <hns at goldelico.com> wrote:
>>>> 
>>>>>> Am 19.03.2019 um 13:16 schrieb H. Nikolaus Schaller <hns at goldelico.com>:
>>> 
>>>>>>>> * GTA04A4:	backlight ok, display shows white pixels only  
>>>>>>> 
>>>>>>> hmm, did a quick test with mainline: older dtb + 5.1-rc1 kernel = display ok
>>>>>>> 5.1-rc1 kernel + dtb-5-1-rc1 (both mainline) = black screen  
>>> 
>>> Ah, I didn't read precisely: "black screen". I get this as well if I eliminate
>>> most Letux patch sets.
>>> 
>>> This means that one or two hacks are not yet upstream...
>>> 
>>>>>> 
>>>> well,
>>>> echo 0 >/sys/class/backlight/backlight/bl_power
>>>> resolved that. Then I had a working display with mainline 5.1-rc1 + dtb-5.1-rc1
>>>> 
>>>> I think we are talking about different problems.
>>> 
>>> Looks so...
>>> 
>>> My main symptom is that I get a /dev/fb0, X server process is running, backlight
>>> is on, but the screen is completely white. And xset dpms force on/off can
>>> turn backlight on&off. But still only white pixels.
> 
> I have now checked and the symptoms are two facets of the same problem.
> 
> When doing my git bisect of linus/master plus adding only 4 of our letux patches,
> I get a black display in the error case which goes completely white when echoing to
> bp_power.
> 
> I never had the backlight staying black but display working.
> 
> But there remains some difference by adding the full letux patch set. I.e. some
> piece of code does have the same side effect as echo 0 >/sys/class/backlight/backlight/bl_power
> 
> So we could probably check
> 
> 	cat /sys/class/backlight/backlight/bl_power
> 
> after boot to automate the bisect (1 = bad, 0 = good).
> 
>>> 
>>> I guess the problem is either the SPI interface to the panel or the pixel
>>> clock/pixel data.
>>> 
>>> I am currently running a bisect to find out more.
>> 
>> First result:
> 
> Here is a new result after repeating with git bisect start '--no-checkout' '--' 'arch/arm' 'include/' 'drivers/'
> 
> 	f90d64483ebd394958841f67f8794ab203b319a7 is the first bad commit 
> 	https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f90d64483ebd394958841f67f8794ab203b319a7
> 
>> 
>> 	67e79a6dc2664a3ef85113440e60f7aaca3c7815 is the first bad commit
>> 
>> i.e.
>> 
>> 	https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=67e79a6dc2664a3ef85113440e60f7aaca3c7815
>> 
>> But what does this have to do with the GTA04 display and backlight power???
> 
> Same question for the new result... This time it is a different merge.
> In both cases a merge of subsystem updates and not a single patch. Strange.
> 
>> 
>> I fear a side-effect of an array out of bounds write like we did have a while ago.
>> 
>> Or I did make a mistake in reporting good/bad to git bisect. Maybe I should repeat.
>> 
>> Note this is using mainline linux (bisected) + letux/compile-fixes + letux/arm_defconfig + letux/Letux + letux/ubi-fs and nothing else.
>> So it does not include many of the Letux hacks.
> 
> So at the moment I have no good idea how to debug it. Maybe we should wait
> until v5.1-rc2 is out. Someone else might have a similar issue or a late
> fix is provided that is missing in v5.1-rc1.

Some more observations (in failed state):

a) panel driver is loaded

root at letux:~# lsmod|fgrep td0
panel_tpo_td028ttec1    16384  3 
omapdss_base           16384  5 connector_analog_tv,encoder_opa362,panel_tpo_td028ttec1,omapdrm,omapdss
root at letux:~# 

b) video cards are initialized

root at letux:~# ls -l /sys/devices/platform/omapdrm.0/drm/card0/card0-*
/sys/devices/platform/omapdrm.0/drm/card0/card0-DPI-1:
total 0
lrwxrwxrwx 1 root root    0 Mar 21 07:11 device -> ../../card0
-r--r--r-- 1 root root 4096 Mar 21 07:11 dpms
-r--r--r-- 1 root root    0 Mar 21 07:11 edid
-r--r--r-- 1 root root 4096 Mar 21 07:11 enabled
-r--r--r-- 1 root root 4096 Mar 21 07:11 modes
drwxr-xr-x 2 root root    0 Mar 21 07:06 power
-rw-r--r-- 1 root root 4096 Mar 21 07:11 status
lrwxrwxrwx 1 root root    0 Mar 21 07:11 subsystem -> ../../../../../../class/drm
-rw-r--r-- 1 root root 4096 Mar 21 06:28 uevent

/sys/devices/platform/omapdrm.0/drm/card0/card0-SVIDEO-1:
total 0
lrwxrwxrwx 1 root root    0 Mar 21 07:11 device -> ../../card0
-r--r--r-- 1 root root 4096 Mar 21 07:11 dpms
-r--r--r-- 1 root root    0 Mar 21 07:11 edid
-r--r--r-- 1 root root 4096 Mar 21 07:11 enabled
-r--r--r-- 1 root root 4096 Mar 21 07:11 modes
drwxr-xr-x 2 root root    0 Mar 21 07:06 power
-rw-r--r-- 1 root root 4096 Mar 21 07:11 status
lrwxrwxrwx 1 root root    0 Mar 21 07:11 subsystem -> ../../../../../../class/drm
-rw-r--r-- 1 root root 4096 Mar 21 06:28 uevent
root at letux:~#

c) the panel seems to be programmed through SPI

root at letux:/sys/bus/spi/drivers/panel-tpo-td028ttec1/spi4.0# for i in statistics/*; do echo $i $(cat $i); done
statistics/bytes 202
statistics/bytes_rx 0
statistics/bytes_tx 202
statistics/errors 0
statistics/messages 48
statistics/spi_async 0
statistics/spi_sync 48
statistics/spi_sync_immediate 48
statistics/timedout 0
statistics/transfer_bytes_histo_0-1 0
statistics/transfer_bytes_histo_1024-2047 0
statistics/transfer_bytes_histo_128-255 0
statistics/transfer_bytes_histo_16-31 0
statistics/transfer_bytes_histo_16384-32767 0
statistics/transfer_bytes_histo_2-3 7
statistics/transfer_bytes_histo_2048-4095 0
statistics/transfer_bytes_histo_256-511 0
statistics/transfer_bytes_histo_32-63 0
statistics/transfer_bytes_histo_32768-65535 0
statistics/transfer_bytes_histo_4-7 41
statistics/transfer_bytes_histo_4096-8191 0
statistics/transfer_bytes_histo_512-1023 0
statistics/transfer_bytes_histo_64-127 0
statistics/transfer_bytes_histo_65536+ 0
statistics/transfer_bytes_histo_8-15 0
statistics/transfer_bytes_histo_8192-16383 0
statistics/transfers 48
statistics/transfers_split_maxsize 0
root at letux:/sys/bus/spi/drivers/panel-tpo-td028ttec1/spi4.0#

BR,
Nikolaus



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