[Bug 68451] [byt dsi] Baytrail/T DSI display not supported on ASUS T100TA

Mon Jul 28 23:34:33 PDT 2014

https://bugzilla.kernel.org/show_bug.cgi?id=68451

--- Comment #65 from Robert R. Howell <rhowell at uwyo.edu> ---
I've discovered what might be a useful clue regarding the cause of the blank
screen after these tablets switch from the EFI to the the i915 console.  The
problem MAY be related to "vblank wait timed out" errors.  

First, on my ASUS T100TA the tablet display always seems to come up properly,
on recent kernels up to and including 3.16-rc7, as long as I do NOT have the
tablet hooked up to an external HDMI monitor.  (More on HDMI later.)  I've
booted with the drm.debug=0x06 parameter and, in contrast to what I describe
below, the T100TA dmesg output NEVER shows "vblank wait timed out errors".

I also have a Toshiba Encore 8 and as I posted above, I originally thought its
display was working OK.  However that was from just one or two (successful)
boots.  Since then on almost all attempts I seem to be having the same problem
that Adam describes for his Dell tablet.  The screen goes blank at the point it
tries to switch from the EFI to the i915 console.  In all of those failed
attempts, when I later examine the dmesg output, I see there have been "vblank
wait timed out" errors while it was in the middle of some drm mode set
operation.  I include a stack trace at the end.  On one occasion where it DID
successfully bring up the screen and I recorded dmesg (and also used
drm.debug), it did NOT show the "vblank wait timed out" error.  I've been
trying MANY times to capture another successful boot to confirm these all have
NO vblank timeout errors, but of course now the machine has decided to always
come up with the blank screen.  Why it very occasionally initializes
successfully (and did so on the first boot or two back on July 12) is something
I just haven't figured out.

The one way I can make the Encore bring up the tablet screen relatively often
is to rapidly press ESCAPE during the boot process.  I've long since removed
the "splash=silent quiet" parameters so this isn't trying to switch back to
console from a graphical screen, but quite often the escape DOES makes the
screen "flash", and then the i915 console does become visible and eventually it
successfully brings up the full X11 graphics.  During these boots sometimes I
see the vblank wait time out error and sometimes I don't.  

The other way I've been able to investigate dmesg output even when the tablet
screen is blank is that I can (with luck) log in by typing blindly.  Then using
xrandr to disable then enable the tablet display does usually make it visible. 
So something in the driver code called by that DOES successfully initialize the
display.  Finally, the Encore (and the T100TA) have micro-hdmi ports which DO
work, which gives me another way in to the system.

So to summarize, 1) the stand-alone T100 always initializes the tablet display
properly and never shows the vblank timeout error, 2) the Encore almost always
comes up with a blank screen and on all those failures DOES show the vblank
error, and 3) on a rare occasion where the Encore did bring up an active
screen, it did NOT show the vblank timeout error.

To add one final point of confusion, although I think this really is a separate
problem, I've discovered that when I do have an external HDMI display connected
to the T100, sometimes the tablet display comes up blank even during the very
first steps where it is displaying the grub menu via the EFI driver.  Perhaps
this is by design, as the HDMI screen is active, although often both screens
are active.  In any case, when I do boot the machine from this
tablet-display-disabled state, later xrandr calls are UNABLE to turn on the
tablet display.  The only way to ensure this does not happen is to start the
T100 with the HDMI disconnected, in which case the tablet display always works.
 Then I can plug in the HDMI either at the grub menu prompt or later.  
Although this appears to be a different "bug" since it happens even before the
i915 driver loads, the fact that the i915 cannot turn on the T100 display
through later xrandr commands (although xrandr reports it HAS turned on)
suggests some critical display initialization step is still missing in that
driver.  I know that is the opposite of what I just said regarding xrandr for
the Encore, but that is what repeated tests show.

Sorry this is such a long message -- but that reflects how confusing the
symptoms seem to be.

Let me know if you need more information.

Bob Howell

---------------------------
dmesg "vblank time out" text from a "bad" Encore boot:

[   14.131000] [drm:drm_mode_getconnector] [CONNECTOR:13:?]
[   14.131014] [drm:drm_mode_getconnector] [CONNECTOR:13:?]
[   14.131152] [drm:drm_mode_getconnector] [CONNECTOR:17:?]
[   14.131161] [drm:drm_mode_getconnector] [CONNECTOR:17:?]
[   14.131200] [drm:drm_mode_getconnector] [CONNECTOR:19:?]
[   14.131210] [drm:drm_mode_getconnector] [CONNECTOR:19:?]
[   14.370598] [drm:drm_mode_addfb] [FB:51]
[   14.370615] [drm:drm_mode_setcrtc] [CRTC:5]
[   14.370625] [drm:drm_mode_setcrtc] [CONNECTOR:19:DSI-1]
[   14.370630] [drm:intel_crtc_set_config] [CRTC:5] [FB:51] #connectors=1 (x y)
(0 0)
[   14.370637] [drm:intel_set_config_compute_mode_changes] computed changes for
[CRTC:5], mode_changed=0, fb_changed=1
[   14.370641] [drm:intel_modeset_stage_output_state] [CONNECTOR:13:HDMI-A-1]
to [CRTC:9]
[   14.370645] [drm:intel_modeset_stage_output_state] [CONNECTOR:19:DSI-1] to
[CRTC:5]
[   14.370653] [drm:valleyview_set_rps] GPU freq request from 178 MHz (191) to
666 MHz (213)
[   14.373548] [drm:i9xx_update_primary_plane] Writing base 00DB5000 00000000 0
0 7680
[   14.425518] ------------[ cut here ]------------
[   14.425575] WARNING: CPU: 1 PID: 644 at
drivers/gpu/drm/i915/intel_display.c:861 intel_wait_for_vblank+0x1f9/0x200
[i915]()
[   14.425579] vblank wait timed out
[   14.425581] Modules linked in: joydev fuse battery acpi_pad ac
intel_powerclamp hid_multitouch hid_sensor_hub coretemp kvm_intel kvm gpio_keys
snd_soc_sst_baytrail_pcm snd_soc_sst_dsp snd_soc_sst_byt_rt5640_mach 8250_dw
snd_soc_rt5640 snd_soc_core snd_compress snd_soc_rl6231 crc32_pclmul regmap_i2c
crc32c_intel snd_pcm snd_timer aesni_intel ablk_helper cryptd lrw gf128mul
glue_helper pcspkr aes_x86_64 toshiba_acpi snd sparse_keymap wmi soundcore
soc_button_array int3403_thermal i2c_hid snd_soc_sst_acpi
i2c_designware_platform i2c_designware_core lpc_ich mfd_core iosf_mbi pwm_lpss
brcmfmac brcmutil cfg80211 rfkill sg dm_mod efivarfs hid_logitech_dj i915
drm_kms_helper drm i2c_algo_bit xhci_hcd button thermal video processor
scsi_dh_alua scsi_dh_emc scsi_dh_rdac scsi_dh_hp_sw scsi_dh mmc_block
sdhci_acpi
[   14.425647]  sdhci mmc_core
[   14.425654] CPU: 1 PID: 644 Comm: Xorg Tainted: G        W    
3.16.0-rc7-rrh-01 #1
[   14.425657] Hardware name: TOSHIBA Encore/Encore, BIOS 1.60 03/06/2014
[   14.425660]  0000000000000009 ffff8800716f3b90 ffffffff815fa786
ffff8800716f3bd8
[   14.425666]  ffff8800716f3bc8 ffffffff810508a8 ffff880033dc0000
00000000001f0040
[   14.425670]  0000000000000a1f 00000000fffba2d9 ffff8800358f5000
ffff8800716f3c28
[   14.425676] Call Trace:
[   14.425687]  [<ffffffff815fa786>] dump_stack+0x4d/0x6f
[   14.425694]  [<ffffffff810508a8>] warn_slowpath_common+0x78/0xa0
[   14.425699]  [<ffffffff81050917>] warn_slowpath_fmt+0x47/0x50
[   14.425730]  [<ffffffffa018d239>] intel_wait_for_vblank+0x1f9/0x200 [i915]
[   14.425758]  [<ffffffffa018f0f4>] intel_pipe_set_base+0x144/0x330 [i915]
[   14.425788]  [<ffffffffa01994de>] intel_crtc_set_config+0x95e/0xda0 [i915]
[   14.425811]  [<ffffffffa00ddff1>] drm_mode_set_config_internal+0x61/0xe0
[drm]
[   14.425831]  [<ffffffffa00e191f>] drm_mode_setcrtc+0xcf/0x580 [drm]
[   14.425847]  [<ffffffffa00d28fc>] drm_ioctl+0x1ec/0x660 [drm]
[   14.425856]  [<ffffffff811a14a0>] do_vfs_ioctl+0x2e0/0x4c0
[   14.425862]  [<ffffffff811aaff9>] ? __fget+0x69/0xb0
[   14.425867]  [<ffffffff811a1701>] SyS_ioctl+0x81/0xa0
[   14.425874]  [<ffffffff816013a9>] system_call_fastpath+0x16/0x1b
[   14.425877] ---[ end trace 0f148e052eb831a3 ]---
[   14.426077] [drm:drm_mode_setcrtc] [CRTC:9]
[   14.426088] [drm:drm_mode_setcrtc] [CONNECTOR:13:HDMI-A-1]
[   14.426093] [drm:intel_crtc_set_config] [CRTC:9] [FB:51] #connectors=1 (x y)
(0 0)
[   14.426098] [drm:intel_set_config_compute_mode_changes] computed changes for
[CRTC:9], mode_changed=0, fb_changed=1
[   14.426102] [drm:intel_modeset_stage_output_state] [CONNECTOR:13:HDMI-A-1]
to [CRTC:9]
[   14.426106] [drm:intel_modeset_stage_output_state] [CONNECTOR:19:DSI-1] to
[CRTC:5]
[   14.426119] [drm:i9xx_update_primary_plane] Writing base 00DB5000 00000000 0
0 7680

-----------Equivalent output during boot which DID bring up Encore display
------
[   17.135744] [drm:drm_mode_getconnector] [CONNECTOR:13:?]
[   17.135758] [drm:drm_mode_getconnector] [CONNECTOR:13:?]
[   17.135810] [drm:drm_mode_getconnector] [CONNECTOR:17:?]
[   17.135819] [drm:drm_mode_getconnector] [CONNECTOR:17:?]
[   17.135857] [drm:drm_mode_getconnector] [CONNECTOR:19:?]
[   17.135867] [drm:drm_mode_getconnector] [CONNECTOR:19:?]
[   17.248502] [drm:drm_mode_addfb] [FB:51]
[   17.248519] [drm:drm_mode_setcrtc] [CRTC:5]
[   17.248528] [drm:drm_mode_setcrtc] [CONNECTOR:19:DSI-1]
[   17.248534] [drm:intel_crtc_set_config] [CRTC:5] [FB:51] #connectors=1 (x y)
(0 0)
[   17.248540] [drm:intel_set_config_compute_mode_changes] computed changes for
[CRTC:5], mode_changed=0, fb_changed=1
[   17.248545] [drm:intel_modeset_stage_output_state] [CONNECTOR:13:HDMI-A-1]
to [CRTC:9]
[   17.248548] [drm:intel_modeset_stage_output_state] [CONNECTOR:19:DSI-1] to
[CRTC:5]
[   17.248557] [drm:valleyview_set_rps] GPU freq request from 178 MHz (191) to
666 MHz (213)
[   17.251673] [drm:i9xx_update_primary_plane] Writing base 00DB5000 00000000 0
0 7680
[   17.255562] [drm:drm_mode_setcrtc] [CRTC:9]
[   17.255573] [drm:drm_mode_setcrtc] [CONNECTOR:13:HDMI-A-1]
[   17.255578] [drm:intel_crtc_set_config] [CRTC:9] [FB:51] #connectors=1 (x y)
(0 0)
[   17.255583] [drm:intel_set_config_compute_mode_changes] computed changes for
[CRTC:9], mode_changed=0, fb_changed=1
[   17.255588] [drm:intel_modeset_stage_output_state] [CONNECTOR:13:HDMI-A-1]
to [CRTC:9]
[   17.255591] [drm:intel_modeset_stage_output_state] [CONNECTOR:19:DSI-1] to
[CRTC:5]
[   17.255602] [drm:i9xx_update_primary_plane] Writing base 00DB5000 00000000 0
0 7680

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