# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1496487418 -7200
# Node ID 166f3658f3145bc5a61a936ac92044d8d3812ebb
# Parent  a9c2c11fc770a7b02137670664915875dbfaca83
Disable and re-enable the line channel when setting the source address, even
though this does not actually appear to be necessary.

diff -r a9c2c11fc770 -r 166f3658f314 vga.S
--- a/vga.S	Tue May 30 00:12:14 2017 +0200
+++ b/vga.S	Sat Jun 03 12:56:58 2017 +0200
@@ -778,9 +778,22 @@
 
 irq_dma_update:
 
+	/* Disable line channel. */
+
+	la $v0, DCH0CON
+	li $v1, 0b10000000
+	sw $v1, CLR($v0)
+
+	/* Update the source address. */
+
 	la $v0, DCH0SSA
 	sw $s2, 0($v0)
 
+	/* Enable line channel. */
+
+	la $v0, DCH0CON
+	sw $v1, SET($v0)
+
 irq_clear_dma:
 
 	/* Clear the DMA interrupt condition. */