SPI DMA based RGB Underglow for STM32 (qmk#7674)

* Initial stash of ws2812 spi driver

* Update comment, add sync backup plan

* Add testing notes to spi ws2812 driver

* Align RGBW error messages

docs/ws2812_driver.md

@@ -14,7 +14,7 @@ These LEDs are called "addressable" because instead of using a wire per color, e
 |----------|--------------------|--------------------|
 | bit bang | :heavy_check_mark: | :heavy_check_mark: |
 | I2C      | :heavy_check_mark: |                    |
-| SPI      |                    | Soon™              |
+| SPI      |                    | :heavy_check_mark: |
 | PWM      |                    | Soon™              |
 
 ## Driver configuration
@@ -40,3 +40,30 @@ Configure the hardware via your config.h:
 #define WS2812_ADDRESS 0xb0 // default: 0xb0
 #define WS2812_TIMEOUT 100 // default: 100
 ```
+
+### SPI
+Targeting STM32 boards where WS2812 support is offloaded to an SPI hardware device. The advantage is that the use of DMA offloads processing of the WS2812 protocol from the MCU. `RGB_DI_PIN` for this driver is the configured SPI MOSI pin. Due to the nature of repurposing SPI to drive the LEDs, the other SPI pins, MISO and SCK, **must** remain unused. To configure it, add this to your rules.mk:
+
+```make
+WS2812_DRIVER = spi
+```
+
+Configure the hardware via your config.h:
+```c
+#define WS2812_SPI SPID1 // default: SPID1
+#define WS2812_SPI_MOSI_PAL_MODE 5 // Pin "alternate function", see the respective datasheet for the appropriate values for your MCU. default: 5
+```
+
+You must also turn on the SPI feature in your halconf.h and mcuconf.h
+
+#### Testing Notes
+
+While not an exhaustive list, the following table provides the scenarios that have been partially validated:
+
+| | SPI1 | SPI2 | SPI3 |
+|-|-|-|-|
+| f072 | ? | B15 :heavy_check_mark: | N/A |
+| f103 | A7 :heavy_check_mark: | B15 :heavy_check_mark: | N/A |
+| f303 | A7 :heavy_check_mark: B5 :heavy_check_mark:  | B15 :heavy_check_mark: | B5 :heavy_check_mark: |
+
+*Other supported ChibiOS boards and/or pins may function, it will be highly chip and configuration dependent.*

drivers/arm/ws2812_spi.c

@@ -1 +1,90 @@
-#error("NOT SUPPORTED")
+#include "quantum.h"
+#include "ws2812.h"
+
+/* Adapted from https://github.com/gamazeps/ws2812b-chibios-SPIDMA/ */
+
+#ifdef RGBW
+#    error "RGBW not supported"
+#endif
+
+// Define the spi your LEDs are plugged to here
+#ifndef WS2812_SPI
+#    define WS2812_SPI SPID1
+#endif
+
+#ifndef WS2812_SPI_MOSI_PAL_MODE
+#    define WS2812_SPI_MOSI_PAL_MODE 5
+#endif
+
+#define BYTES_FOR_LED_BYTE 4
+#define NB_COLORS 3
+#define BYTES_FOR_LED (BYTES_FOR_LED_BYTE * NB_COLORS)
+#define DATA_SIZE (BYTES_FOR_LED * RGBLED_NUM)
+#define RESET_SIZE 200
+#define PREAMBLE_SIZE 4
+
+static uint8_t txbuf[PREAMBLE_SIZE + DATA_SIZE + RESET_SIZE] = {0};
+
+/*
+ * As the trick here is to use the SPI to send a huge pattern of 0 and 1 to
+ * the ws2812b protocol, we use this helper function to translate bytes into
+ * 0s and 1s for the LED (with the appropriate timing).
+ */
+static uint8_t get_protocol_eq(uint8_t data, int pos) {
+    uint8_t eq = 0;
+    if (data & (1 << (2 * (3 - pos))))
+        eq = 0b1110;
+    else
+        eq = 0b1000;
+    if (data & (2 << (2 * (3 - pos))))
+        eq += 0b11100000;
+    else
+        eq += 0b10000000;
+    return eq;
+}
+
+static void set_led_color_rgb(LED_TYPE color, int pos) {
+    uint8_t* tx_start = &txbuf[PREAMBLE_SIZE];
+
+    for (int j = 0; j < 4; j++) tx_start[BYTES_FOR_LED * pos + j] = get_protocol_eq(color.g, j);
+    for (int j = 0; j < 4; j++) tx_start[BYTES_FOR_LED * pos + BYTES_FOR_LED_BYTE + j] = get_protocol_eq(color.r, j);
+    for (int j = 0; j < 4; j++) tx_start[BYTES_FOR_LED * pos + BYTES_FOR_LED_BYTE * 2 + j] = get_protocol_eq(color.b, j);
+}
+
+void ws2812_init(void) {
+#if defined(USE_GPIOV1)
+    palSetLineMode(RGB_DI_PIN, PAL_MODE_STM32_ALTERNATE_PUSHPULL);
+#else
+    palSetLineMode(RGB_DI_PIN, PAL_MODE_ALTERNATE(WS2812_SPI_MOSI_PAL_MODE) | PAL_STM32_OTYPE_PUSHPULL);
+#endif
+
+    // TODO: more dynamic baudrate
+    static const SPIConfig spicfg = {
+        NULL, PAL_PORT(RGB_DI_PIN), PAL_PAD(RGB_DI_PIN),
+        SPI_CR1_BR_1 | SPI_CR1_BR_0  // baudrate : fpclk / 8 => 1tick is 0.32us (2.25 MHz)
+    };
+
+    spiAcquireBus(&WS2812_SPI);     /* Acquire ownership of the bus.    */
+    spiStart(&WS2812_SPI, &spicfg); /* Setup transfer parameters.       */
+    spiSelect(&WS2812_SPI);         /* Slave Select assertion.          */
+}
+
+void ws2812_setleds(LED_TYPE* ledarray, uint16_t leds) {
+    static bool s_init = false;
+    if (!s_init) {
+        ws2812_init();
+        s_init = true;
+    }
+
+    for (uint8_t i = 0; i < leds; i++) {
+        set_led_color_rgb(ledarray[i], i);
+    }
+
+    // Send async - each led takes ~0.03ms, 50 leds ~1.5ms, animations flushing faster than send will cause issues.
+    // Instead spiSend can be used to send synchronously (or the thread logic can be added back).
+#ifdef WS2812_SPI_SYNC
+    spiSend(&WS2812_SPI, sizeof(txbuf) / sizeof(txbuf[0]), txbuf);
+#else
+    spiStartSend(&WS2812_SPI, sizeof(txbuf) / sizeof(txbuf[0]), txbuf);
+#endif
+}