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reform/audio: remove DAC vol limit; discharge HP caps on init

Capless mode was mistakingly enabled, with 500Ω on VRIO to
disable the audio, which most likely cause the original
"issue" of speakers playback switching off and on when on
full volume. Fix that. Also set impedance on VRIO to 20kΩ.

Discharge HP caps on init to cause less pop.

--- a/sys/src/cmd/reform/audio.c

+++ b/sys/src/cmd/reform/audio.c

@@ -52,13 +52,7 @@

 static void

 dactoggle(Out *, int on)

 {

-	/*

-	 * Jack detect becomes extremely unstable when playing on spk and the

-	 * volume is very high - DAC start to switch back and forth between two

-	 * outputs.  Solve this by always attenuating by -6dB and somewhat limiting

-	 * the volume on DAC ("master") - to 0xf9 instead of 0xff (max).

-	 */

-	wr(0x05, 1<<7 | (!on)<<3);

+	wr(0x05, (!on)<<3);

 }

 static void

@@ -82,7 +76,7 @@

 static Out out[Nout] =

 {

-	[Dac] = {"master", 0x0a, 0xf9, 0, dactoggle, 0},

+	[Dac] = {"master", 0x0a, 0xff, 0, dactoggle, 0},

 	[Hp] = {"hp", 0x02, 0x7f, 3<<5, nil, 0},

 	[Spk] = {"spk", 0x28, 0x7f, 3<<3, classdspk, 0},

 };

@@ -181,6 +175,7 @@

 	toggle(out+Dac, 0);

 	wr(0x1c, 1<<7 | 1<<4 | 1<<3 | 1<<2); /* Vmid/r bias; Vgs/r on; Vmid soft start */

+	wr(0x1d, 1<<6 | 0<<4); /* discharge HP caps; 400Ω */

 	wr(0x19, 0<<7); /* Vmid off, Vref off */

 	sleep(500);

 	wr(0x0f, 0); /* reset registers to default */

@@ -197,14 +192,15 @@

 	wr(0x17, 1<<8 | 3<<6 | 1<<0); /* thermal shutdown on; avdd=3.3v; slow clock on */

 	wr(0x1c, 1<<7 | 1<<4 | 1<<3 | 1<<2); /* Vmid/r bias; Vgs/r on; Vmid soft start */

+	wr(0x1d, 0); /* stop HP caps discharge */

 	wr(0x19, 1<<7); /* start Vmid (playback) */

 	sleep(650);

 	wr(0x1c, 1<<3); /* done with anti-pop */

 	wr(0x19, 1<<7 | 1<<6); /* Vref on */

-	wr(0x09, 1<<6); /* adclrc → gpio (for jack detect output) */

+	wr(0x09, 1<<6); /* ADCLRC → gpio (for jack detect output) */

 	wr(0x30, 3<<4 | 2<<2 | 1<<1); /* gpio jack detect out; JD2 jack detect in; Tsense on */

-	wr(0x1b, 1<<3); /* HP_[LR] responsive to jack detect */

+	wr(0x1b, 1<<6 | 0<<3 | 0<<0); /* capless mode disabled; 20kΩ; 44.1/48kHz */

 	wr(0x18, 1<<6); /* HP switch on; high = HP */

 	/* turn on all outputs */