Fix various issues with MMC1.

mos-platform/nes-mmc1/CMakeLists.txt

@@ -26,5 +26,5 @@ add_platform_object_file(nes-mmc1-init-prg-rom-32-banked-o
 add_platform_object_file(nes-mmc1-init-prg-ram-0-o
   init-prg-ram-0.o init-prg-ram-0.s)
 
-add_platform_library(nes-mmc1-c bank.c)
+add_platform_library(nes-mmc1-c bank.c bank.s)
 merge_libraries(nes-mmc1-c common-c)

mos-platform/nes-mmc1/_prg-rom-banked.ld

@@ -60,6 +60,7 @@ SECTIONS {
   .prg_rom_0 :  OVERLAY { *(.prg_rom_0  .prg_rom_0.*)  } >prg_rom_0_vma  AT>prg_rom_0_lma
   .prg_rom_1 :  OVERLAY { *(.prg_rom_1  .prg_rom_1.*)  } >prg_rom_1_vma  AT>prg_rom_1_lma
   .prg_rom_2 :  OVERLAY { *(.prg_rom_2  .prg_rom_2.*)  } >prg_rom_2_vma  AT>prg_rom_2_lma
+  .prg_rom_3 :  OVERLAY { *(.prg_rom_3  .prg_rom_3.*)  } >prg_rom_3_vma  AT>prg_rom_3_lma
   .prg_rom_4 :  OVERLAY { *(.prg_rom_4  .prg_rom_4.*)  } >prg_rom_4_vma  AT>prg_rom_4_lma
   .prg_rom_5 :  OVERLAY { *(.prg_rom_5  .prg_rom_5.*)  } >prg_rom_5_vma  AT>prg_rom_5_lma
   .prg_rom_6 :  OVERLAY { *(.prg_rom_6  .prg_rom_6.*)  } >prg_rom_6_vma  AT>prg_rom_6_lma
@@ -71,4 +72,5 @@ SECTIONS {
   .prg_rom_12 : OVERLAY { *(.prg_rom_12 .prg_rom_12.*) } >prg_rom_12_vma AT>prg_rom_12_lma
   .prg_rom_13 : OVERLAY { *(.prg_rom_13 .prg_rom_13.*) } >prg_rom_13_vma AT>prg_rom_13_lma
   .prg_rom_14 : OVERLAY { *(.prg_rom_14 .prg_rom_14.*) } >prg_rom_14_vma AT>prg_rom_14_lma
+  .prg_rom_15 : OVERLAY { *(.prg_rom_15 .prg_rom_15.*) } >prg_rom_15_vma AT>prg_rom_15_lma
 }

mos-platform/nes-mmc1/bank.c

@@ -28,18 +28,18 @@
 
 #include <peekpoke.h>
 
-static char PRG_BANK;
-static char CHR_BANK0;
-static char CHR_BANK1;
-static char MMC1_CTRL_NMI;
+__attribute__((section(".zp.bss"))) char _PRG_BANK;
+__attribute__((section(".zp.bss"))) char _CHR_BANK0;
+__attribute__((section(".zp.bss"))) char _CHR_BANK1;
+__attribute__((section(".zp.data"))) char _MMC1_CTRL_NMI = 0x1f;
 
-char _CHR_BANK0_CUR;
+__attribute__((section(".zp.bss"))) char _CHR_BANK0_CUR;
 extern __attribute__((
     weak, alias("_CHR_BANK0_CUR"))) volatile const char CHR_BANK0_CUR;
-char _CHR_BANK1_CUR;
+__attribute__((section(".zp.bss"))) char _CHR_BANK1_CUR;
 extern __attribute__((
     weak, alias("_CHR_BANK1_CUR"))) volatile const char CHR_BANK1_CUR;
-char _MMC1_CTRL_CUR;
+__attribute__((section(".zp.bss"))) char _MMC1_CTRL_CUR;
 extern __attribute__((
     weak, alias("_MMC1_CTRL_CUR"))) volatile const char MMC1_CTRL_CUR;
 
@@ -49,9 +49,12 @@ extern __attribute__((
 #define MMC1_PRG 0xe000
 
 // Incrementing a 0xff ROM byte resets the MMC.
-__attribute__((used)) static const char reset_mmc1_byte = 0xff;
+__attribute__((used)) const char __reset_mmc1_byte = 0xff;
+static void reset_shift_register(void) {
+  __attribute__((leaf)) asm volatile("inc __reset_mmc1_byte");
+}
 
-static volatile char IN_PROGRESS = 0;
+volatile char _IN_PROGRESS = 0;
 
 __attribute__((always_inline)) static inline void
 mmc1_register_write(unsigned addr, char val) {
@@ -68,81 +71,63 @@ mmc1_register_write(unsigned addr, char val) {
 
 __attribute__((always_inline)) static inline void
 mmc1_register_write_retry(unsigned addr, char val) {
-  // May be interrupting another write, so reset the shift register.
-  asm volatile("inc reset_mmc1_byte");
   do {
-    IN_PROGRESS = 1;
+    _IN_PROGRESS = 1;
+    reset_shift_register();
     mmc1_register_write(addr, val);
-    // Was interrupted, and we may have written a few bytes afterwards, so reset
-    // the shift register and try again until successful.
-    if (!IN_PROGRESS)
-      asm volatile("inc reset_mmc1_byte");
-  } while (!IN_PROGRESS);
-  IN_PROGRESS = 0;
+  } while (!_IN_PROGRESS);
+  _IN_PROGRESS = 0;
 }
 
-__attribute__((weak)) void banked_call(char bankId, void (*method)(void)) {
+__attribute__((noinline, weak)) void banked_call(char bank_id,
+                                                 void (*method)(void)) {
   char old_id = get_prg_bank();
+  set_prg_bank(bank_id);
   method();
   set_prg_bank(old_id);
 }
 
-__attribute__((weak)) void set_prg_bank(char bank_id) {
-  PRG_BANK = bank_id;
-  mmc1_register_write_retry(MMC1_PRG, bank_id);
+__attribute__((weak)) void set_chr_bank_0(char bank_id) {
+  _CHR_BANK0 = bank_id;
 }
 
-__attribute__((weak)) char get_prg_bank(void) { return PRG_BANK; }
-
-__attribute__((weak)) void set_chr_bank_0(char bank_id) { CHR_BANK0 = bank_id; }
-
-__attribute__((weak)) void set_chr_bank_1(char bank_id) { CHR_BANK1 = bank_id; }
+__attribute__((weak)) void set_chr_bank_1(char bank_id) {
+  _CHR_BANK1 = bank_id;
+}
 
 __attribute__((weak)) void split_chr_bank_0(char bank_id) {
-  asm volatile("inc reset_mmc1_byte");
+  reset_shift_register();
   mmc1_register_write(MMC1_CHR0, bank_id);
-  IN_PROGRESS = 0;
+  _IN_PROGRESS = 0;
   _CHR_BANK0_CUR = bank_id;
 }
 
 __attribute__((weak)) void split_chr_bank_1(char bank_id) {
-  asm volatile("inc reset_mmc1_byte");
+  reset_shift_register();
   mmc1_register_write(MMC1_CHR1, bank_id);
-  IN_PROGRESS = 0;
+  _IN_PROGRESS = 0;
   _CHR_BANK1_CUR = bank_id;
 }
 
 __attribute__((weak)) void set_chr_bank_0_retry(char bank_id) {
-  CHR_BANK0 = bank_id;
+  _CHR_BANK0 = bank_id;
   mmc1_register_write_retry(MMC1_CHR0, bank_id);
 }
 
 __attribute__((weak)) void set_chr_bank_1_retry(char bank_id) {
-  CHR_BANK1 = bank_id;
+  _CHR_BANK1 = bank_id;
   mmc1_register_write_retry(MMC1_CHR1, bank_id);
 }
 
 __attribute__((weak)) void set_mirroring(char mirroring) {
-  MMC1_CTRL_NMI &= 0b11100;
-  MMC1_CTRL_NMI |= mirroring & 0b11;
+  _MMC1_CTRL_NMI &= 0b11100;
+  _MMC1_CTRL_NMI |= mirroring & 0b11;
 }
 
 __attribute__((weak)) void set_mmc1_ctrl(char value) {
-  MMC1_CTRL_NMI = value;
+  _MMC1_CTRL_NMI = value;
   mmc1_register_write_retry(MMC1_CTRL, value);
   _MMC1_CTRL_CUR = value;
 }
 
 // some things deleted
-
-void __nmi_bank_handler(void) {
-  asm volatile("inc reset_mmc1_byte");
-  mmc1_register_write(MMC1_CHR0, CHR_BANK0);
-  _CHR_BANK0_CUR = CHR_BANK0;
-  mmc1_register_write(MMC1_CHR1, CHR_BANK1);
-  _CHR_BANK1_CUR = CHR_BANK0;
-  mmc1_register_write(MMC1_CTRL, MMC1_CTRL_NMI);
-  _MMC1_CTRL_CUR = MMC1_CTRL_NMI;
-  IN_PROGRESS = 0;
-}
-__attribute__((weak, alias("__nmi_bank_handler"))) void nmi_bank_handler(void);

mos-platform/nes-mmc1/bank.h

@@ -44,25 +44,16 @@ extern volatile const char MMC1_CTRL_CUR;
 // Switch to another bank and call this function.
 // Note: Using banked_call to call a second function from within
 // another banked_call is safe.
-void banked_call(char bankId, void (*method)(void));
-
-// Internal function used by banked_call(), don't call this directly.
-// Switch to the given bank, and keep track of the current bank, so
-// that we may jump back to it as needed.
-void bank_push(char bankId);
-
-// Internal function used by banked_call(), don't call this directly.
-// Go back to the last bank pushed on using bank_push.
-void bank_pop(void);
+void banked_call(char bank_id, void (*method)(void));
 
 // Switch to the given bank (to $8000-bfff). Your prior bank is not saved.
 // Can be used for reading data with a function in the fixed bank.
 // bank_id: The bank to switch to.
-void set_prg_bank(char bank_id);
+__attribute__((leaf)) void set_prg_bank(char bank_id);
 
 // Get the current PRG bank at $8000-bfff.
 // returns: The current bank.
-char get_prg_bank(void);
+__attribute__((leaf)) char get_prg_bank(void);
 
 // Set the current 1st 4k chr bank to the bank with this id.
 // this will take effect at the next frame
@@ -121,9 +112,6 @@ void set_mmc1_ctrl(char value);
 
 // some things deleted
 
-// To be called on NMI to set graphics-affecting banks.
-void nmi_bank_handler(void);
-
 #ifdef __cplusplus
 }
 #endif

mos-platform/nes-mmc1/bank.s

@@ -0,0 +1,88 @@
+; Copyright 2022 LLVM-MOS Project
+; Licensed under the Apache License, Version 2.0 with LLVM Exceptions.
+; See https://github.com/llvm-mos/llvm-mos-sdk/blob/main/LICENSE for license
+; information.
+;
+; Copyright 2019 Doug Fraker
+; Copyright 2018 Christopher Parker
+;
+; Permission is hereby granted, free of charge, to any person obtaining a copy
+; of this software and associated documentation files (the "Software"), to deal
+; in the Software without restriction, including without limitation the rights
+; to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+; copies of the Software, and to permit persons to whom the Software is
+; furnished to do so, subject to the following conditions:
+;
+; The above copyright notice and this permission notice shall be included in
+; all copies or substantial portions of the Software.
+;
+; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+; IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+; FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+; AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+; LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+; OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+; SOFTWARE.
+
+MMC1_CTRL	= $8000
+MMC1_CHR0	= $a000
+MMC1_CHR1	= $c000
+MMC1_PRG	= $e000
+
+; macro to write to an mmc1 register, which goes one bit at a time, 5 bits wide.
+.macro mmc1_register_write addr
+	.rept 4
+		sta \addr
+		lsr
+	.endr
+	sta \addr
+.endmacro
+
+.section .text.nmi_bank_handler,"ax",@progbits
+.globl __nmi_bank_handler
+.weak nmi_bank_handler
+nmi_bank_handler:
+__nmi_bank_handler:
+	inc __reset_mmc1_byte
+	lda _CHR_BANK0
+	sta _CHR_BANK0_CUR
+	mmc1_register_write MMC1_CHR0
+	lda _CHR_BANK1
+	sta _CHR_BANK1_CUR
+	mmc1_register_write MMC1_CHR1
+	lda _MMC1_CTRL_NMI
+	sta _MMC1_CTRL_CUR
+	mmc1_register_write MMC1_CTRL
+	lda #0
+	sta _IN_PROGRESS
+	rts
+
+.section .text.get_prg_bank,"ax",@progbits
+.globl __get_prg_bank
+.weak get_prg_bank
+__get_prg_bank:
+get_prg_bank:
+	lda _PRG_BANK
+	rts
+
+.section .text.set_prg_bank,"ax",@progbits
+.globl __set_prg_bank
+.weak set_prg_bank
+__set_prg_bank:
+set_prg_bank:
+	tay
+.Lset:
+	inc __reset_mmc1_byte
+	ldx #1
+	stx _IN_PROGRESS
+	mmc1_register_write MMC1_PRG
+	ldx _IN_PROGRESS
+	beq .Lretry
+	dex
+	stx _IN_PROGRESS
+	sty _PRG_BANK
+	rts
+.Lretry:
+	tya
+	jmp .Lset
+

mos-platform/nes-mmc1/common.ld

@@ -67,6 +67,23 @@ MEMORY {
   chr_rom_29 : ORIGIN = 0x0201d000, LENGTH = __chr_rom_size >= 128 ? 0x1000 : 0
   chr_rom_30 : ORIGIN = 0x0201e000, LENGTH = __chr_rom_size >= 128 ? 0x1000 : 0
   chr_rom_31 : ORIGIN = 0x0201f000, LENGTH = __chr_rom_size >= 128 ? 0x1000 : 0
+
+  chr_rom_0_1   : ORIGIN = 0x02000000, LENGTH = __chr_rom_size >= 8   ? 0x2000 : 0
+  chr_rom_2_3   : ORIGIN = 0x02002000, LENGTH = __chr_rom_size >= 16  ? 0x2000 : 0
+  chr_rom_4_5   : ORIGIN = 0x02004000, LENGTH = __chr_rom_size >= 32  ? 0x2000 : 0
+  chr_rom_6_7   : ORIGIN = 0x02006000, LENGTH = __chr_rom_size >= 32  ? 0x2000 : 0
+  chr_rom_8_9   : ORIGIN = 0x02008000, LENGTH = __chr_rom_size >= 64  ? 0x2000 : 0
+  chr_rom_10_11 : ORIGIN = 0x0200a000, LENGTH = __chr_rom_size >= 64  ? 0x2000 : 0
+  chr_rom_12_13 : ORIGIN = 0x0200c000, LENGTH = __chr_rom_size >= 64  ? 0x2000 : 0
+  chr_rom_14_15 : ORIGIN = 0x0200e000, LENGTH = __chr_rom_size >= 64  ? 0x2000 : 0
+  chr_rom_16_17 : ORIGIN = 0x02010000, LENGTH = __chr_rom_size >= 128 ? 0x2000 : 0
+  chr_rom_18_19 : ORIGIN = 0x02012000, LENGTH = __chr_rom_size >= 128 ? 0x2000 : 0
+  chr_rom_20_21 : ORIGIN = 0x02014000, LENGTH = __chr_rom_size >= 128 ? 0x2000 : 0
+  chr_rom_22_23 : ORIGIN = 0x02016000, LENGTH = __chr_rom_size >= 128 ? 0x2000 : 0
+  chr_rom_24_25 : ORIGIN = 0x02018000, LENGTH = __chr_rom_size >= 128 ? 0x2000 : 0
+  chr_rom_26_27 : ORIGIN = 0x0201a000, LENGTH = __chr_rom_size >= 128 ? 0x2000 : 0
+  chr_rom_28_29 : ORIGIN = 0x0201c000, LENGTH = __chr_rom_size >= 128 ? 0x2000 : 0
+  chr_rom_30_31 : ORIGIN = 0x0201e000, LENGTH = __chr_rom_size >= 128 ? 0x2000 : 0
 }
 
 SECTIONS {
@@ -107,6 +124,23 @@ SECTIONS {
   .chr_rom_29 : { KEEP(*(.chr_rom_29 .chr_rom_29.*)) } >chr_rom_29
   .chr_rom_30 : { KEEP(*(.chr_rom_30 .chr_rom_30.*)) } >chr_rom_30
   .chr_rom_31 : { KEEP(*(.chr_rom_31 .chr_rom_31.*)) } >chr_rom_31
+
+  .chr_rom_0_1   : { KEEP(*(.chr_rom_0_1   .chr_rom_0_1.*)) }   >chr_rom_0_1
+  .chr_rom_2_3   : { KEEP(*(.chr_rom_2_3   .chr_rom_2_3.*)) }   >chr_rom_2_3
+  .chr_rom_4_5   : { KEEP(*(.chr_rom_4_5   .chr_rom_4_5.*)) }   >chr_rom_4_5
+  .chr_rom_6_7   : { KEEP(*(.chr_rom_6_7   .chr_rom_6_7.*)) }   >chr_rom_6_7
+  .chr_rom_8_9   : { KEEP(*(.chr_rom_8_9   .chr_rom_8_9.*)) }   >chr_rom_8_9
+  .chr_rom_10_11 : { KEEP(*(.chr_rom_10_11 .chr_rom_10_11.*)) } >chr_rom_10_11
+  .chr_rom_12_13 : { KEEP(*(.chr_rom_12_13 .chr_rom_12_13.*)) } >chr_rom_12_13
+  .chr_rom_14_15 : { KEEP(*(.chr_rom_14_15 .chr_rom_14_15.*)) } >chr_rom_14_15
+  .chr_rom_16_17 : { KEEP(*(.chr_rom_16_17 .chr_rom_16_17.*)) } >chr_rom_16_17
+  .chr_rom_18_19 : { KEEP(*(.chr_rom_18_19 .chr_rom_18_19.*)) } >chr_rom_18_19
+  .chr_rom_20_21 : { KEEP(*(.chr_rom_20_21 .chr_rom_20_21.*)) } >chr_rom_20_21
+  .chr_rom_22_23 : { KEEP(*(.chr_rom_22_23 .chr_rom_22_23.*)) } >chr_rom_22_23
+  .chr_rom_24_25 : { KEEP(*(.chr_rom_24_25 .chr_rom_24_25.*)) } >chr_rom_24_25
+  .chr_rom_26_27 : { KEEP(*(.chr_rom_26_27 .chr_rom_26_27.*)) } >chr_rom_26_27
+  .chr_rom_28_29 : { KEEP(*(.chr_rom_28_29 .chr_rom_28_29.*)) } >chr_rom_28_29
+  .chr_rom_30_31 : { KEEP(*(.chr_rom_30_31 .chr_rom_30_31.*)) } >chr_rom_30_31
 }
 
 /* Provide a mask selecting the significant bits of a CHR bank number. */