The table below contains some typical issues related to the DRM/KMS framework, as well as solutions or debugging methods.
If your issue is not listed, refer to the articles in the DRM/KMS or troubleshooting grids categories.
| Symptom | Resolution |
|---|---|
./myQtApplication Could not queue DRM page flip! (Permission denied) Could not queue DRM page flip! (Permission denied) |
The psplash-drm userland splash screen is running and is then the DRM master, avoiding other DRM applications to access to DRM/KMS. Stop this psplash-drm application with the command below before running your use case: psplash-drm-quit Note: You may need to enter "export QT_QPA_EGLFS_ALWAYS_SET_MODE=1" before running your Qt application. For further information, refer to the Qt documentation. |
echo 32 > /sys/class/backlight/5a000000.dsi.0/brightness sh: write error: No such device or address |
On this board, the panel backlight is related to a MIPI® DSI panel. This backlight can be modified only if the panel is already powered on. That is probably not the case here. |
I/TC: Resumed
E/TC:0 tzc_it_handler:79 TZC permission failure
E/TC:0 dump_fail_filter:417 Overrun violation on filter 0
E/TC:0 dump_fail_filter:420 Permission violation on filter 0
E/TC:0 dump_fail_filter:425 Violation @0xdce1ff80, non-secure
unprivileged read, AXI ID 403
E/TC:0 Panic at core/arch/arm/plat-stm32mp1/plat_tzc400.c:84
<tzc_it_handler>
E/TC:0 TEE load address @ 0xde000000
|
This trace indicates that the TZC internal peripheral is detecting a "permission violation" made by the master whose AXI ID is 0x403. It corresponds to the LTDC internal peripheral (LTDC NSAID=0b0011. For further information, refer to the STM32 reference manuals).
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dmesg | grep -i ltdc [ 341.85] [drm] ltdc fifo underrun: please verify display mode [ 1045.48] [drm] ltdc fifo underrun: please verify display mode |
The "LTDC fifo underrun" messages occur when the LTDC input fifo is not filled fast enough. These messages may appear occasionally (during the display initialization for instance) and are often non-blocking. However, it happens that these messages are numerous, generating display problems like visual artifacts and this can come from:
To fix this problem, check your DDR & AXI system parameters, adjust the DVFS policy, decrease the display resolution, use a single LTDC layer for the display composition, monitor the system with Linux monitoring tools and the DDR usage with DDRPERFM internal peripheral, "simplify" the use case...
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