Align dma buffers (#248)

* Do not loop forever

If the TPS65185 are unable to start the PWRGOOD signal will never assert.

* Align DMA buffers

The size of the buffers used by DMA must be word aligned. If the
width of the screen is not aligned we increase the buffer slightly.

src/epd_driver/board/epd_board_v6.c

@@ -201,7 +201,16 @@ static void epd_board_poweron(epd_ctrl_state_t *state) {
   // give the IC time to powerup and set lines
   vTaskDelay(1);
 
+  int tries = 0;
   while (!(pca9555_read_input(config_reg.port, 1) & CFG_PIN_PWRGOOD)) {
+    if (tries >= 500) {
+      ESP_LOGE("epdiy", "Power enable failed! INT status: 0x%X 0x%X",
+        tps_read_register(config_reg.port, TPS_REG_INT1),
+        tps_read_register(config_reg.port, TPS_REG_INT2)
+      );
+      return;
+    }
+    tries++;
     vTaskDelay(1);
   }
 
@@ -215,7 +224,6 @@ static void epd_board_poweron(epd_ctrl_state_t *state) {
   };
   epd_board_set_ctrl(state, &mask);
 
-  int tries = 0;
   while (!((tps_read_register(config_reg.port, TPS_REG_PG) & 0xFA) == 0xFA)) {
     if (tries >= 500) {
       ESP_LOGE("epdiy", "Power enable failed! PG status: %X", tps_read_register(config_reg.port, TPS_REG_PG));

src/epd_driver/i2s_data_bus.c

@@ -49,9 +49,10 @@ static gpio_num_t start_pulse_pin;
 
 /// Initializes a DMA descriptor.
 static void fill_dma_desc(volatile lldesc_t *dmadesc, uint8_t *buf,
-                          uint32_t epd_row_width) {
-  dmadesc->size = epd_row_width / 4;
-  dmadesc->length = epd_row_width / 4;
+                          uint32_t buf_size, uint32_t buf_length) {
+  assert(buf_length % 4 == 0);  // Must be word aligned
+  dmadesc->size = buf_size;
+  dmadesc->length = buf_length;
   dmadesc->buf = buf;
   dmadesc->eof = 1;
   dmadesc->sosf = 1;
@@ -68,6 +69,13 @@ uint32_t dma_desc_addr() {
          0x000FFFFF;
 }
 
+// Helper function to help align values
+static size_t align_up(size_t x, size_t a)
+{
+    return (size_t)(x + ((size_t)a - 1)) & ~(size_t)(a-1);
+}
+
+
 /// Set up a GPIO as output and route it to a signal.
 static void gpio_setup_out(int gpio, int sig, bool invert) {
   if (gpio == -1)
@@ -241,14 +249,15 @@ void i2s_bus_init(i2s_bus_config *cfg, uint32_t epd_row_width) {
   dev->timing.val = 0;
 
   // Allocate DMA descriptors
-  i2s_state.buf_a = heap_caps_malloc(epd_row_width / 4, MALLOC_CAP_DMA);
-  i2s_state.buf_b = heap_caps_malloc(epd_row_width / 4, MALLOC_CAP_DMA);
+  const size_t buf_size = align_up(epd_row_width/4, 4);  // Buf size must be word aligned
+  i2s_state.buf_a = heap_caps_malloc(buf_size, MALLOC_CAP_DMA);
+  i2s_state.buf_b = heap_caps_malloc(buf_size, MALLOC_CAP_DMA);
   i2s_state.dma_desc_a = heap_caps_malloc(sizeof(lldesc_t), MALLOC_CAP_DMA);
   i2s_state.dma_desc_b = heap_caps_malloc(sizeof(lldesc_t), MALLOC_CAP_DMA);
 
   // and fill them
-  fill_dma_desc(i2s_state.dma_desc_a, i2s_state.buf_a, epd_row_width);
-  fill_dma_desc(i2s_state.dma_desc_b, i2s_state.buf_b, epd_row_width);
+  fill_dma_desc(i2s_state.dma_desc_a, i2s_state.buf_a, epd_row_width/4, buf_size);
+  fill_dma_desc(i2s_state.dma_desc_b, i2s_state.buf_b, epd_row_width/4, buf_size);
 
   // enable "done" interrupt
   SET_PERI_REG_BITS(I2S_INT_ENA_REG(1), I2S_OUT_DONE_INT_ENA_V, 1,