From a90d8f476d542a5c2b76f015f4eea93d04acf6b0 Mon Sep 17 00:00:00 2001
From: Kyle Cardoza <Kyle.Cardoza@gmail.com>
Date: Thu, 28 Mar 2024 23:23:04 -0400
Subject: [PATCH] Work on VERA API and interrupts

---
 include/drivers/vera.h |  2 ++
 src/drivers/vera.s     | 54 ++++++++++++++++++++++++++++++++++++++++++
 src/drivers/vera2.c    | 22 ++++-------------
 3 files changed, 61 insertions(+), 17 deletions(-)

diff --git a/include/drivers/vera.h b/include/drivers/vera.h
index fadfc2c..7d61753 100644
--- a/include/drivers/vera.h
+++ b/include/drivers/vera.h
@@ -51,6 +51,8 @@ extern void vera_set_addr0_decrement(bool state);
 
 extern void vera_set_addr1_decrement(bool state);
 
+extern void vera_set_addr0_incr1(uint32_t addr);
+
 uint8_t vera_read_byte(uint32_t addr);
 
 uint16_t vera_read_word(uint32_t addr);
diff --git a/src/drivers/vera.s b/src/drivers/vera.s
index b5ee4e0..d2d8d6f 100644
--- a/src/drivers/vera.s
+++ b/src/drivers/vera.s
@@ -16,6 +16,7 @@
 			.public vera_poke_data0
 			.public vera_poke_data1
 			.public vera_set_addr0_auto_increment
+			.public vera_set_addr0_incr1
 			.public vera_set_addr1_auto_increment
 			.public vera_set_addr0_decrement
 			.public vera_set_addr1_decrement
@@ -309,3 +310,56 @@ vera_set_addr1_decrement_done:
 	long_a
 	plb
 	rts
+
+; Optimization: Combine the most common setting for
+; addr0: Set an address, and set INCR0 to 1,
+; and DECR0 to 0.
+vera_set_addr0_incr1:
+	phb
+	short_a
+	pha
+
+	; Set the data bank to 0
+	lda #0
+	pha
+	plb
+
+	; Set ADDRSEL to 0.
+	lda #0b00000001
+	trb 0xDF05
+
+	; Set DECR0 to 0 and INCR0 to 0
+	lda #0b11111000
+	trb 0xDF02
+	lda #0b00010000
+	tsb 0xDF02
+
+	; Set the low byte of the address
+	lda _Dp+0
+	sta 0xDF00
+
+	; Set the mid byte of the address
+	lda _Dp+1
+	sta 0xDF01
+
+	; Set the high bit of the address
+	lda _Dp+2
+	and #0b00000001
+
+	; If the high bit in A is set, then branch
+	bne addr0_incr1_high_bit_set
+	; Else clear the lowest bit of ADDR0_H
+	lda #0b00000001
+	trb 0xDF03
+	; And exit
+	bra addr0_incr1_done
+
+addr0_incr1_high_bit_set:
+	; Set the lowest bit of ADDR0_H
+	lda #0b00000001
+	tsb 0xDF03
+
+addr0_incr1_done:
+	plb
+	long_a
+	rts
diff --git a/src/drivers/vera2.c b/src/drivers/vera2.c
index 6ab3822..cbdd8bf 100644
--- a/src/drivers/vera2.c
+++ b/src/drivers/vera2.c
@@ -23,9 +23,7 @@ vera_read_byte(uint32_t addr)
 uint16_t
 vera_read_word(uint32_t addr)
 {
-	vera_set_data0_address(addr);
-	vera_set_addr0_auto_increment(ADDR_INCREMENT_1);
-	vera_set_addr0_decrement(false);
+	vera_set_addr0_incr1(addr);
 	uint8_t data_low = vera_peek_data0();
 	uint8_t data_high = vera_peek_data0();
 	return (uint16_t)((data_high << 8) & data_low);
@@ -43,9 +41,7 @@ vera_write_byte(uint32_t addr, uint8_t value)
 void
 vera_write_word(uint32_t addr, uint16_t value)
 {
-	vera_set_data0_address(addr);
-	vera_set_addr0_auto_increment(ADDR_INCREMENT_1);
-	vera_set_addr0_decrement(false);
+	vera_set_addr0_incr1(addr);
 	vera_poke_data0((uint8_t)(value & 0x00FF));
 	vera_poke_data0((uint8_t)(value & 0xFF00) >> 8);
 }
@@ -54,10 +50,7 @@ void
 vera_read(void *dest, uint32_t src, size_t length)
 {
 	uint8_t *dst = dest;
-
-	vera_set_data0_address(src);
-	vera_set_addr0_auto_increment(ADDR_INCREMENT_1);
-	vera_set_addr0_decrement(false);
+	vera_set_addr0_incr1(src);
 
 	for (size_t i = 0; i < length; i += 1) {
 		dst[i] = vera_peek_data0();
@@ -68,10 +61,7 @@ void
 vera_write(uint32_t dest, void *src, size_t length)
 {
 	uint8_t *source = src;
-
-	vera_set_data0_address(dest);
-	vera_set_addr0_auto_increment(ADDR_INCREMENT_1);
-	vera_set_addr0_decrement(false);
+	vera_set_addr0_incr1(dest);
 
 	for (size_t i = 0; i < length; i += 1) {
 		vera_poke_data0(source[i]);
@@ -81,9 +71,7 @@ vera_write(uint32_t dest, void *src, size_t length)
 void
 vera_memset(uint32_t addr, uint8_t value, size_t length)
 {
-	vera_set_data0_address(addr);
-	vera_set_addr0_auto_increment(ADDR_INCREMENT_1);
-	vera_set_addr0_decrement(false);
+	vera_set_addr0_incr1(addr);
 
 	for (size_t i = 0; i < length; i += 1) {
 		vera_poke_data0(value);