subsys: display: glitchy display in lvgl demo for stm32f746g_disco

[ric96]

I just built the subsys/display/lvgl demo for the stm32f746g_disco board and the screen periodically glitches. I does not seem to be related to the main loops sleep duration, i tried playing around with it.

Video:

https://github.com/zephyrproject-rtos/zephyr/assets/5900740/704c561d-7cf8-4716-ac72-d44c133adbca

[ric96]

It does not seem to be related to lvgl, i tried the driver/display sample as well with the same issue. So might be worth adding the area: Display tag as well. I have tried copying over the display clock values from the STM32Cube sample application LTDC_Display_1Layer but the issue persists.

diff --git a/boards/arm/stm32f746g_disco/stm32f746g_disco.dts b/boards/arm/stm32f746g_disco/stm32f746g_disco.dts
index 93054659df..3f9266448e 100644
--- a/boards/arm/stm32f746g_disco/stm32f746g_disco.dts
+++ b/boards/arm/stm32f746g_disco/stm32f746g_disco.dts
@@ -273,12 +273,13 @@ zephyr_udc0: &usbotg_fs {
                pixelclk-active = <0>;
                hsync-active = <0>;
                vsync-active = <0>;
-               hsync-len = <1>;
+               hsync-len = <41>;
                vsync-len = <10>;
-               hback-porch = <43>;
-               vback-porch = <12>;
-               hfront-porch = <8>;
-               vfront-porch = <4>;
+               hback-porch = <13>;
+               vback-porch = <2>;
+               hfront-porch = <32>;
+               vfront-porch = <2>;
+               clock-frequency = <9500000>;
        };
        def-back-color-red = <0xFF>;
        def-back-color-green = <0xFF>;

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[dolence]

Hi! I'm having the same issue on STM32H7. Did you managed to solve this?

[kartben]

Can confirm that F746G Disco is glitchy for me as well.

[dolence]

@erwango would be possible to reopen this? 3 persons with the same problem.

[coskunergan]

using 800x480px with F746G Disco and I have the same problem. Looks like this issue needs a solution.

[kartben]

Maybe #66513 will help?

[kartben]

@erwango would be possible to reopen this? 3 persons with the same problem.

Done

[erwango]

@ajarmouni-st Can you have a look ?

[dolence]

Maybe #66513 will help?

I'm very new to Zephyr and my git knowledge resumes to cloning repositories. How could I test this PR?

[ajarmouni-st]

@dolence https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[kartben]

@dolence you may also install the GitHub CLI and you can then simply gh pr checkout 66513 (running west update is of course recommended after that)

[dolence]

I have tried #66513 and while the double framebuffer was moved to external SDRAM the flickering becomes worst and the CPU usage has increased.

Memory region         Used Size  Region Size  %age Used
           FLASH:      287508 B         1 MB     27.42%
             RAM:       38040 B       512 KB      7.26%
            QSPI:          0 GB       256 MB      0.00%
           SRAM1:          0 GB       128 KB      0.00%
           SRAM2:          0 GB       128 KB      0.00%
           SRAM3:          0 GB        32 KB      0.00%
           SRAM4:          0 GB        64 KB      0.00%
          SDRAM2:       4000 KB         8 MB     48.83%
        IDT_LIST:          0 GB         2 KB      0.00%

https://github.com/zephyrproject-rtos/zephyr/assets/5223003/3b6a2884-a7b0-490c-9ce1-5a7a85723dd0

[ric96]

I have tried #66513 and while the double framebuffer was moved to external SDRAM the flickering becomes worst and the CPU usage has increased.

Memory region         Used Size  Region Size  %age Used
           FLASH:      287508 B         1 MB     27.42%
             RAM:       38040 B       512 KB      7.26%
            QSPI:          0 GB       256 MB      0.00%
           SRAM1:          0 GB       128 KB      0.00%
           SRAM2:          0 GB       128 KB      0.00%
           SRAM3:          0 GB        32 KB      0.00%
           SRAM4:          0 GB        64 KB      0.00%
          SDRAM2:       4000 KB         8 MB     48.83%
        IDT_LIST:          0 GB         2 KB      0.00%

flickering.mp4

you need to remove zephyr,memory-attr from devicetree

[dolence]

you need to remove zephyr,memory-attr from devicetree

Thank you. That solved the flickering. The CPU usage is around 34%, with 10 FPS. Maybe if enabling DMA2D this could be better. Also, text are uglier than before, as you described.

[cameled]

you need to remove zephyr,memory-attr from devicetree

Thank you. That solved the flickering. The CPU usage is around 34%, with 10 FPS. Maybe if enabling DMA2D this could be better. Also, text are uglier than before, as you described.

You can try it with below config:

# PATH: modules/lib/gui/lvgl/Kconfig
CONFIG_LV_USE_GPU_STM32_DMA2D=y
# Please update 'stm32h747xx.h`.
CONFIG_LV_GPU_DMA2D_CMSIS_INCLUDE="stm32h747xx.h"

[dolence]

you need to remove zephyr,memory-attr from devicetree

Thank you. That solved the flickering. The CPU usage is around 34%, with 10 FPS. Maybe if enabling DMA2D this could be better. Also, text are uglier than before, as you described.

You can try it with below config:

# PATH: modules/lib/gui/lvgl/Kconfig
CONFIG_LV_USE_GPU_STM32_DMA2D=y
# Please update 'stm32h747xx.h`.
CONFIG_LV_GPU_DMA2D_CMSIS_INCLUDE="stm32h747xx.h"

I have tried this before but many warnings was being shown:

/home/dolence/zephyrproject/modules/lib/gui/lvgl/src/core/../draw/stm32_dma2d/lv_gpu_stm32_dma2d.h:56:13: warning: 'lv_draw_stm32_dma2d_blend' declared 'static' but never defined [-Wunused-function]
   56 | static void lv_draw_stm32_dma2d_blend(lv_draw_ctx_t * draw_ctx, const lv_draw_sw_blend_dsc_t * dsc);
      |             ^~~~~~~~~~~~~~~~~~~~~~~~~
/home/dolence/zephyrproject/modules/lib/gui/lvgl/src/core/../draw/stm32_dma2d/lv_gpu_stm32_dma2d.h:57:13: warning: 'lv_draw_stm32_dma2d_buffer_copy' declared 'static' but never defined [-Wunused-function]
   57 | static void lv_draw_stm32_dma2d_buffer_copy(lv_draw_ctx_t * draw_ctx,
      |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dolence/zephyrproject/modules/lib/gui/lvgl/src/core/../draw/stm32_dma2d/lv_gpu_stm32_dma2d.h:60:17: warning: 'lv_draw_stm32_dma2d_img' declared 'static' but never defined [-Wunused-function]
   60 | static lv_res_t lv_draw_stm32_dma2d_img(lv_draw_ctx_t * draw_ctx, const lv_draw_img_dsc_t * img_dsc,
      |                 ^~~~~~~~~~~~~~~~~~~~~~~
/home/dolence/zephyrproject/modules/lib/gui/lvgl/src/core/../draw/stm32_dma2d/lv_gpu_stm32_dma2d.h:62:13: warning: 'lv_gpu_stm32_dma2d_wait_cb' declared 'static' but never defined [-Wunused-function]
   62 | static void lv_gpu_stm32_dma2d_wait_cb(lv_draw_ctx_t * draw_ctx);
      |             ^~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dolence/zephyrproject/modules/lib/gui/lvgl/src/core/../draw/stm32_dma2d/lv_gpu_stm32_dma2d.h:63:13: warning: 'lv_draw_stm32_dma2d_img_decoded' declared 'static' but never defined [-Wunused-function]
   63 | static void lv_draw_stm32_dma2d_img_decoded(lv_draw_ctx_t * draw_ctx, const lv_draw_img_dsc_t * img_dsc,

[cameled]

you need to remove zephyr,memory-attr from devicetree

Thank you. That solved the flickering. The CPU usage is around 34%, with 10 FPS. Maybe if enabling DMA2D this could be better. Also, text are uglier than before, as you described.

You can try it with below config:

# PATH: modules/lib/gui/lvgl/Kconfig
CONFIG_LV_USE_GPU_STM32_DMA2D=y
# Please update 'stm32h747xx.h`.
CONFIG_LV_GPU_DMA2D_CMSIS_INCLUDE="stm32h747xx.h"

I have tried this before but many warnings was being shown:

/home/dolence/zephyrproject/modules/lib/gui/lvgl/src/core/../draw/stm32_dma2d/lv_gpu_stm32_dma2d.h:56:13: warning: 'lv_draw_stm32_dma2d_blend' declared 'static' but never defined [-Wunused-function]
   56 | static void lv_draw_stm32_dma2d_blend(lv_draw_ctx_t * draw_ctx, const lv_draw_sw_blend_dsc_t * dsc);
      |             ^~~~~~~~~~~~~~~~~~~~~~~~~
/home/dolence/zephyrproject/modules/lib/gui/lvgl/src/core/../draw/stm32_dma2d/lv_gpu_stm32_dma2d.h:57:13: warning: 'lv_draw_stm32_dma2d_buffer_copy' declared 'static' but never defined [-Wunused-function]
   57 | static void lv_draw_stm32_dma2d_buffer_copy(lv_draw_ctx_t * draw_ctx,
      |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dolence/zephyrproject/modules/lib/gui/lvgl/src/core/../draw/stm32_dma2d/lv_gpu_stm32_dma2d.h:60:17: warning: 'lv_draw_stm32_dma2d_img' declared 'static' but never defined [-Wunused-function]
   60 | static lv_res_t lv_draw_stm32_dma2d_img(lv_draw_ctx_t * draw_ctx, const lv_draw_img_dsc_t * img_dsc,
      |                 ^~~~~~~~~~~~~~~~~~~~~~~
/home/dolence/zephyrproject/modules/lib/gui/lvgl/src/core/../draw/stm32_dma2d/lv_gpu_stm32_dma2d.h:62:13: warning: 'lv_gpu_stm32_dma2d_wait_cb' declared 'static' but never defined [-Wunused-function]
   62 | static void lv_gpu_stm32_dma2d_wait_cb(lv_draw_ctx_t * draw_ctx);
      |             ^~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dolence/zephyrproject/modules/lib/gui/lvgl/src/core/../draw/stm32_dma2d/lv_gpu_stm32_dma2d.h:63:13: warning: 'lv_draw_stm32_dma2d_img_decoded' declared 'static' but never defined [-Wunused-function]
   63 | static void lv_draw_stm32_dma2d_img_decoded(lv_draw_ctx_t * draw_ctx, const lv_draw_img_dsc_t * img_dsc,

Same to me. I found there no change with this config.

[dolence]

Probably some bug in DMA2D activation?

[ric96]

Probably some bug in DMA2D activation?

better to open a separate issue regarding this.

[cameled]

Probably some bug in DMA2D activation?

Looks modules/lib/gui/lvgl/src/draw/stm32_dma2d/lv_gpu_stm32_dma2d.c write dma2d register directly.

[kartben]

I doubt any of the "GPU" accelerations available upstream are currently supported, and they probably should be hidden from Zephyr's Kconfig? /cc @faxe1008

[faxe1008]

I doubt any of the "GPU" accelerations available upstream are currently supported, and they probably should be hidden from Zephyr's Kconfig? /cc @faxe1008

With a bit of patching you can make this work. PXP support should be relatively trivial https://github.com/lvgl/lvgl/blob/master/src%2Fdraw%2Fnxp%2Fpxp%2Flv_pxp_osa.c. The only plugging point missing really is a semaphore impl. Since v9 will come with an osal that already provides mutex abstraction maybe adding a semaphore in there is a cheap way to unlock those drivers?

Will take a stab on this next week. Thanks for bumping me into this.

[kartben]

Will take a stab on this next week. Thanks for bumping me into this.

w00t, awesome! And LVGL9 will make things even easier for us in this area, if I understand correctly?

[hanh-nn]

Hi! I have the same problem and removed zephyr,memory-attr but it didn't work for me. I describe my problem here #66993. Did I miss anything?

[faxe1008]

@hanh-nn does this PR solve your issue: https://github.com/zephyrproject-rtos/zephyr/pull/66513?

[hanh-nn]

@hanh-nn PR này có giải quyết được vấn đề của bạn không: #66513?

My mistake. It's worked. Thanks

[erwango]

@ric96 Can you confirm this is solved by https://github.com/zephyrproject-rtos/zephyr/pull/66513 ?