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1. Article purpose[edit source]
This article aims to explain how to use the secure display hardware feature thanks to:
- the STM32 LTDC internal peripheral
- the following secure hardware internal peripherals:
- on STM32MP13x lines
, the STM32 ETZPC internal peripheral - on STM32MP25x lines , the STM32 RIFSC internal peripheral
- on STM32MP13x lines
- the STM32 OP-TEE framework and its related libutee library[1] that offers services to Trusted Applications (TA) including the Trusted User Interface (TUI) API
This article also explains how to configure and use a Trusted User Interface / Trusted Application example for demonstrating the secure display hardware feature.
2. Prerequisites[edit source]
To run the Trusted User Interface / Trusted Application example, required hardware boards and software stacks are listed below:
- On STM32MP13x lines : The STM32MP135x-DK Discovery kit
- On STM32MP25x lines : The STM32MP257x-EV1 Evaluation board or the STM32MP257x-DK Discovery kit
- A display panel or the HDMI interface
- An OpenSTLinux distribution
3. LTDC Secure layer description[edit source]
On STM32MP13x lines , the LTDC layer2 can be set as secure (under ETZPC control), whereas the layer1 is always non-secure.
On STM32MP25x lines , the LTDC layer3 can be set as secure (under RIFSC internal peripheral control), whereas layer1 and layer2 are always non-secure, with grouped regs and additional interrupt set:
- The RISUP differentiates the access right of accesses performed toward the following RIF protected peripheral ID:
- "LTDC common": LTDC common registers, about panel info, synchronization, interface
- "LTDC_L1L2" (layer 1 and 2): for the window of any two default applications
- "LTDC_L3": LTDC layer 3, for the window of a potentially secure application, or any default application if there is no secure layer
- "LTDC_ROT": LTDC rotation, with information about the rotation buffers
- The RIMU differentiates the bus transactions emitted by the following AXI masters:
- "RIMU_L1L2": read access only for layer 1 and 2, always non-protected
- "RIMU_L3": read access only for layer 3, potentially protected
- "RIMU_ROT": write of blended pixels, and read of to-be-rotated pixels, potentially protected, because containing blended pixels of the protected layer 3
4. Related softwares and Configurations[edit source]
5. = Device Tree[edit source]
5.1. OP-TEE[edit source]
header file of LTDC HAL module
5.2. Linux kernel[edit source]
5.3. Userland Trusted Application example[edit source]
6. Debug and Traces[edit source]
7. How to run the TUI TA example[edit source]
Boot the board, then use the optee-tui-client binary example, using the following commands:
Get the help information:
optee-tui-client
Usage:
--print-screen-info
--blank-screen <color> (value in ARGB format, ex. 0xFF112233)
--display-image <x>,<y>,<width>,<height>,<path> (file in raw ARGB format)
--draw-pin-pad
Get the display information:
optee-tui-client --print-screen-info D/TA: TA_InvokeCommandEntryPoint:160 result: 0 D/TA: TA_InvokeCommandEntryPoint:160 result: 0 width: 1024 height: 600 width DPI: 160 height DPI: 160 color depth: 0 D/TA: TA_InvokeCommandEntryPoint:160 result: 0
optee-tui-client --blank-screen 0xFF0000 D/TA: TA_InvokeCommandEntryPoint:160 result: 0 D/TA: TA_InvokeCommandEntryPoint:160 result: 0 Hit Ctrl-C to quit ^C
optee-tui-client --draw-pin-pad D/TA: TA_InvokeCommandEntryPoint:160 result: 0 D/TA: TA_InvokeCommandEntryPoint:160 result: -65529 TEEC_InvokeCommand 7 failed with code 0xffff0007 origin 0x4