From 02053924100ddb8617f2d3cbd5b3d5e842cef8c3 Mon Sep 17 00:00:00 2001
From: cinap_lenrek <cinap_lenrek@felloff.net>
Date: Tue, 27 Oct 2020 15:16:03 +0100
Subject: [PATCH] audiohda: make it work with qemu (thanks mischief)

the driver was not using irb interrupts
and was just polling the irb write pointer
to wait for command completion.

this is not supported by qemu.

qemu requires the use of irb interrupt handshake
and it refuses to accept the next command until we
acknowledge the irb interrupt.
---
 sys/src/9/pc/audiohda.c | 28 +++++++++++++++++++++-------
 1 file changed, 21 insertions(+), 7 deletions(-)

diff --git a/sys/src/9/pc/audiohda.c b/sys/src/9/pc/audiohda.c
index 56bb06ec8..92c7eedde 100644
--- a/sys/src/9/pc/audiohda.c
+++ b/sys/src/9/pc/audiohda.c
@@ -462,10 +462,9 @@ waitup32(Ctlr *ctlr, int reg, uint mask, uint set)
 static int
 hdacmd(Ctlr *ctlr, uint request, uint reply[2])
 {
-	uint rp, wp;
-	uint re;
-	int wait;
-	
+	uint rp, wp, re;
+	int wait, ret;
+
 	re = csr16(ctlr, Rirbwp);
 	rp = csr16(ctlr, Corbrp);
 	wp = (csr16(ctlr, Corbwp) + 1) % ctlr->corbsize;
@@ -476,15 +475,22 @@ hdacmd(Ctlr *ctlr, uint request, uint reply[2])
 	ctlr->corb[wp] = request;
 	coherence();
 	csr16(ctlr, Corbwp) = wp;
+
+	ret = 0;
 	for(wait=0; wait < Maxrirbwait; wait++){
 		if(csr16(ctlr, Rirbwp) != re){
 			re = (re + 1) % ctlr->rirbsize;
 			memmove(reply, &ctlr->rirb[re*2], 8);
-			return 1;
+			ret = 1;
+			break;
 		}
 		microdelay(1);
 	}
-	return 0;
+
+	/* reset intcnt for qemu */
+	csr8(ctlr, Rirbsts) = Rirbrover|Rirbrint;
+
+	return ret;
 }
 
 static int
@@ -1732,7 +1738,15 @@ hdastart(Ctlr *ctlr)
 	csr32(ctlr, Rirblbase) = pa;
 	csr32(ctlr, Rirbubase) = pa >> 32;
 	csr16(ctlr, Rirbwp) = Rirbptrrst;
-	csr8(ctlr, Rirbctl) = Rirbdma;
+
+	/*
+	 * qemu requires interrupt handshake,
+	 * even tho we just poll the irb write
+	 * pointer for command completion.
+	 */
+	csr16(ctlr, Rintcnt) = 1;
+	csr8(ctlr, Rirbctl) = Rirbdma|Rirbint;
+
 	waitup8(ctlr, Rirbctl, Rirbdma, Rirbdma);
 	
 	/* enable interrupts */