feat(draw): add NemaGFX rendering backend (#7002)

Co-authored-by: Ioannis Markopoulos <Ioannis_Markopoulos@amat.com>

docs/integration/chip/stm32.rst

@@ -270,6 +270,8 @@ A minimal example using STM32CubeIDE, HAL, and CMSISv1 (FreeRTOS).
      lv_display_flush_ready(display);
    }
 
+.. _dma2d:
+
 DMA2D Support
 -------------
 
@@ -289,3 +291,5 @@ instead of "busywait" while waiting for a DMA2D transfer to complete.
 If ``LV_USE_DRAW_DMA2D_INTERRUPT`` is enabled then you are required to call
 :cpp:expr:`lv_draw_dma2d_transfer_complete_interrupt_handler` whenever the DMA2D
 "transfer complete" global interrupt is received.
+
+If your STM device has a Nema GPU, you can use the :ref:`Nema GFX renderer <stm32_nema_gfx>` instead.

docs/overview/renderers/index.rst

@@ -12,3 +12,4 @@ Renderers and GPUs
     stm32_dma2d
     vglite
     vg_lite
+    nema_gfx

docs/overview/renderers/nema_gfx.rst

@@ -0,0 +1,73 @@
+.. _stm32_nema_gfx:
+
+===================================
+NemaGFX Acceleration (AKA NeoChrom)
+===================================
+
+Some of the more powerful STM32 MCUs such as the
+STM32U5 feature a 2.5D GPU which can natively draw most
+LVGL primitives.
+
+Get Started with the Riverdi STM32U5 5-inch Display
+***************************************************
+
+`lv_port_riverdi_stm32u5 <https://github.com/lvgl/lv_port_riverdi_stm32u5>`__
+is a ready-to-use port for the Riverdi STM32 5.0" Embedded Display
+(STM32U599NJH6Q or STM32U5A9NJH6Q) which has Nema enabled.
+Follow the instructions in the readme to get started.
+
+Usage and Configuration
+***********************
+
+Enable the renderer by setting :c:macro:`LV_USE_NEMA_GFX` to ``1`` in
+lv_conf.h. If using :c:macro:`LV_USE_NEMA_VG`,
+set :c:macro:`LV_NEMA_GFX_MAX_RESX` and :c:macro:`LV_NEMA_GFX_MAX_RESY`
+to the size of the display you will be using so that enough static
+memory will be reserved for VG. Without VG, more task types will be
+performed by the software renderer.
+
+"libs/nema_gfx" contains pre-compiled binaries for the Nema GPU
+drivers. In `lv_port_riverdi_stm32u5 <https://github.com/lvgl/lv_port_riverdi_stm32u5>`__
+the project is already configured to link the binaries when building.
+With a different STM32CubeIDE project, you can configure the libraries to be linked
+by right-clicking the project in the "Project Explorer" sidebar, clicking
+"Properties", navigating to "C/C++ Build", "Settings", "MCU G++ Linker", and then
+"Libraries". Add an entry under "Libraries (-l)" that is "nemagfx-float-abi-hard".
+Add an entry under "Library search path (-L)" which is a path to
+"libs/nema_gfx/lib/core/cortex_m33/gcc" e.g.
+"${workspace_loc:/${ProjName}/Middlewares/LVGL/lvgl/libs/nema_gfx/lib/core/cortex_m33/gcc}".
+You will also want to add the "libs/nema_gfx/include" directory to your include
+search paths. Under "MCU GCC Compiler", "Include paths", add an entry to "Include paths (-I)"
+which is a path to "libs/nema_gfx/include" e.g.
+"${workspace_loc:/${ProjName}/Middlewares/LVGL/lvgl/libs/nema_gfx/include}".
+Click "Apply and Close".
+
+32 and 16 bit :c:macro:`LV_COLOR_DEPTH` is supported.
+
+At the time of writing, :c:macro:`LV_USE_OS` support is experimental
+and not yet working in
+`lv_port_riverdi_stm32u5 <https://github.com/lvgl/lv_port_riverdi_stm32u5>`__
+
+"src/draw/nema_gfx/lv_draw_nema_gfx_hal.c" implements the HAL functionality
+required by Nema to allocate memory and lock resources (in this implementation,
+no locking is done). It may conflict with existing definitions
+if you have an existing Nema HAL implementation. You may
+simply be able to remove yours.
+
+DMA2D
+*****
+
+The Nema renderer uses DMA2D to flush in parallel with rendering in
+`lv_port_riverdi_stm32u5 <https://github.com/lvgl/lv_port_riverdi_stm32u5>`__.
+
+If your STM does not have the Nema GPU, it may still support
+DMA2D. DMA2D is a simple peripheral which can draw fills
+and images independently of the CPU.
+See the LVGL :ref:`DMA2D support <dma2d>`.
+
+API
+***
+
+:ref:`lv_draw_nema_gfx_h`
+
+:ref:`lv_draw_nema_gfx_utils_h`