From df0272b7465777a17813a7b4d93ba9d51354d7ab Mon Sep 17 00:00:00 2001
From: Charlie Birks <charlie@daft.games>
Date: Sun, 26 Feb 2023 19:28:33 +0000
Subject: [PATCH] pico: automatically allocate dma channels/pio sms for audio

audio setup claims the channel passed in so we claim an unused channel/sm, then immediately unclaim it
---
 32blit-pico/audio_i2s.cpp | 15 +++++++++++++--
 32blit-pico/audio_pwm.cpp | 14 ++++++++++++--
 2 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/32blit-pico/audio_i2s.cpp b/32blit-pico/audio_i2s.cpp
index b78c17278..79bef69e2 100644
--- a/32blit-pico/audio_i2s.cpp
+++ b/32blit-pico/audio_i2s.cpp
@@ -1,11 +1,15 @@
 #include "audio.hpp"
 #include "config.h"
 
+#include "hardware/dma.h"
+#include "hardware/pio.h"
 #include "pico/audio_i2s.h"
 #define AUDIO_SAMPLE_FREQ 44100
 
 #include "audio/audio.hpp"
 
+#define audio_pio __CONCAT(pio, PICO_AUDIO_I2S_PIO)
+
 static audio_buffer_pool *audio_pool = nullptr;
 
 void init_audio() {
@@ -23,11 +27,18 @@ void init_audio() {
   struct audio_buffer_pool *producer_pool = audio_new_producer_pool(&producer_format, 4, 441);
   const struct audio_format *output_format;
 
+  uint8_t dma_channel = dma_claim_unused_channel(true);
+  uint8_t pio_sm = pio_claim_unused_sm(audio_pio, true);
+
+  // audio_i2s_setup claims
+  dma_channel_unclaim(dma_channel);
+  pio_sm_unclaim(audio_pio, pio_sm);
+
   struct audio_i2s_config config = {
     .data_pin = PICO_AUDIO_I2S_DATA_PIN,
     .clock_pin_base = PICO_AUDIO_I2S_CLOCK_PIN_BASE,
-    .dma_channel = 1,
-    .pio_sm = 1,
+    .dma_channel = dma_channel,
+    .pio_sm = pio_sm,
   };
 
   output_format = audio_i2s_setup(&audio_format, &config);
diff --git a/32blit-pico/audio_pwm.cpp b/32blit-pico/audio_pwm.cpp
index 87028b9c9..76d8d12e9 100644
--- a/32blit-pico/audio_pwm.cpp
+++ b/32blit-pico/audio_pwm.cpp
@@ -3,12 +3,15 @@
 
 #include "pico/audio_pwm.h"
 #include "hardware/clocks.h"
+#include "hardware/dma.h"
 #include "hardware/pio.h"
 
 #define AUDIO_SAMPLE_FREQ 22050
 
 #include "audio/audio.hpp"
 
+#define audio_pio __CONCAT(pio, PICO_AUDIO_I2S_PIO)
+
 static audio_buffer_pool *audio_pool = nullptr;
 
 void init_audio() {
@@ -26,11 +29,18 @@ void init_audio() {
   struct audio_buffer_pool *producer_pool = audio_new_producer_pool(&producer_format, 4, 441);
   const struct audio_format *output_format;
 
+  uint8_t dma_channel = dma_claim_unused_channel(true);
+  uint8_t pio_sm = pio_claim_unused_sm(audio_pio, true);
+
+  // audio_i2s_setup claims
+  dma_channel_unclaim(dma_channel);
+  pio_sm_unclaim(audio_pio, pio_sm);
+
   struct audio_pwm_channel_config audio_pwm_config = {
     .core = {
       .base_pin = PICO_AUDIO_PWM_MONO_PIN,
-      .dma_channel = 1,
-      .pio_sm = 1,
+      .dma_channel = dma_channel,
+      .pio_sm = pio_sm,
     },
     .pattern = 3,
   };