Attempt to initialize PWM for CPU fan

src/board/system76/galp3-c/pwm.c

@@ -3,6 +3,26 @@
 void pwm_init(void) {
     // Set T0CHSEL to TACH0A and T1CHSEL to TACH1A
     TSWCTLR = 0;
-    // Turn on the CPU fan at full blast (temperature control TODO)
-    DCR2 = 0xFF;
+
+    // Disable PWM
+    ZTIER = 0;
+
+    // Set prescaler to 1159 + 1
+    C6CPRS = 0x87;
+    C6MCPRS = 0x04;
+
+    // Set cycle time to 255 + 1
+    CTR2 = 0xFF;
+
+    // Turn on the CPU fan at half blast (temperature control TODO)
+    DCR2 = 0x80;
+
+    // Set gating clock source
+    PCSGR = 0xFF;
+
+    // Set PWM2 output to use C6CPRS / CTR2
+    PCSSGL = (0b10 << 4);
+
+    // Enable PWM
+    ZTIER = (1 << 1);
 }