Use task driven PWM for CTPC until ARM can provide automatic configuration (#6928)

* Use task driven PWM for CTPC until ARM can provide automatic configuration

* Update CTPC docs to cover backlight

docs/proton_c_conversion.md

@@ -19,3 +19,13 @@ Before being able to compile, you may get some errors about `PORTB/DDRB`, etc no
 The Proton C only has one on-board LED (C13), and by default, the TXLED (D5) is mapped to it. If you want the RXLED (B0) mapped to it instead, add this like to your `config.h`:
 
     #define CONVERT_TO_PROTON_C_RXLED
+
+## Feature Conversion
+
+These are defaults based on what has been implemented for ARM boards.
+
+| Feature                             | Notes                                                                                                            |
+|-------------------------------------|------------------------------------------------------------------------------------------------------------------|
+| [Audio](feature_audio.md)           | Enabled                                                                                                          |  
+| [RGB Lighting](feature_rgblight.md) | Disabled                                                                                                         |
+| [Backlight](feature_backlight.md)   | Forces [task driven PWM](feature_backlight.md#software-pwm-driver) until ARM can provide automatic configuration |

quantum/stm32/proton_c.mk

@@ -3,7 +3,11 @@
 # These are defaults based on what has been implemented for ARM boards
 AUDIO_ENABLE = yes
 RGBLIGHT_ENABLE = no
-BACKLIGHT_ENABLE = no
+
+# Force task driven PWM until ARM can provide automatic configuration
+ifneq ($(strip $(BACKLIGHT_ENABLE)), no)
+	BACKLIGHT_ENABLE = software
+endif
 
 # The rest of these settings shouldn't change