TouchGFX 4.21.1 Causing Distortion on Moving Images

[afergan]

I have custom clock widget in my project and its working fine on version 4.20 but when i upgraded it to 4.21.0 or 4.21.1 causing distortion on clock hands.

When I investigate the issue I saw that SCB_CleanInvalidateDCache() function removed from TouchGFXGeneratedHAL::flushFrameBuffer function. Here is the old function 4.20 has;

void TouchGFXGeneratedHAL::flushFrameBuffer(const touchgfx::Rect& rect)

{

    HAL::flushFrameBuffer(rect);

    // If the framebuffer is placed in Write Through cached memory (e.g. SRAM) then

    // the DCache must be flushed prior to DMA2D accessing it. That's done

    // using the function SCB_CleanInvalidateDCache(). Remember to enable "CPU Cache" in the

    // "System Core" settings for "Cortex M7" in CubeMX in order for this function call to work.

    if (SCB->CCR & SCB_CCR_DC_Msk)

    {

        SCB_CleanInvalidateDCache();

    }

}

When I add this manually its working fine. I didnt understand why they removed this part of code in new version.

There is 2 more functions doing same cache clean;

void TouchGFXGeneratedHAL::InvalidateCache()

{

    // If the framebuffer is placed in Write Through cached memory (e.g. SRAM) then

    // the DCache must be flushed prior to DMA2D accessing it. That's done

    // using the function SCB_CleanInvalidateDCache(). Remember to enable "CPU Cache" in the

    // "System Core" settings for "Cortex M7" in CubeMX in order for this function call to work.

    if (SCB->CCR & SCB_CCR_DC_Msk)

    {

        SCB_CleanInvalidateDCache();

    }

}

void TouchGFXGeneratedHAL::FlushCache()

{

    // If the framebuffer is placed in Write Through cached memory (e.g. SRAM) then

    // the DCache must be flushed prior to DMA2D accessing it. That's done

    // using the function SCB_CleanInvalidateDCache(). Remember to enable "CPU Cache" in the

    // "System Core" settings for "Cortex M7" in CubeMX in order for this function call to work.

    if (SCB->CCR & SCB_CCR_DC_Msk)

    {

        SCB_CleanInvalidateDCache();

    }

}

But I can't see any call for this functions. Is this a migration issue or something wrong with my project?

Thanks.

[Osman SOYKURT]

Hello afergan,

Which TBS is your project based on ? I'll try to investigate on this issue..

/Osman

[afergan]

Hi @Osman SOYKURT​ ,

 

I'm using custom board not ready to use ones. I have STM32H743VIT6 on this board and using LTDC + DMA2D for filling the screen. And ICache and DCache are enabled in my project.

 

On TouchGFX 4.20 TouchGFXGeneratedHAL::flushFrameBuffer have SCB_CleanInvalidateDCache(); call inside by default. But after updating 4.21 this function call removed. I can still add it manually and its working but I couldn't understand why this line was removed.

[unsigned_char_array]

Indeed. I have the same question. In the documentation of TouchGFX it says these methods are called by the framework, but they aren't.

https://support.touchgfx.com/docs/development/board-bring-up/how-to/02-cpu-running

"When the state transit from HARDWARE to SOFTWARE it will call the virtual method void touchgfx::HAL::InvalidateCache() and when the state transitions from SOFTWARE to HARDWARE it will call the virtual method void touchgfx::HAL::FlushCache(). The functionality of these two functions is left for the user to implement in the derived HAL class."
Maybe I don't fully understand what they mean with the transition. It uses either sw or hw rendering as far as I know. Now I always clear the cache in flushFrameBuffer, but maybe that is not needed?

[Yoann KLEIN]

Hello @afergan​,

Please take a look at this article, it explains how the switch mechanism between HW/SW rendering works.

/Yoann