prioritize joybus, cpu_has_uart flag

fw/rtl/cpu/cpu_soc.sv

@@ -72,12 +72,16 @@ module cpu_soc (
         .usb_pwren(usb_pwren)
     );
 
-    cpu_uart cpu_uart_inst (
-        .sys(sys),
-        .bus(bus.at[sc64::ID_CPU_UART].device),
-        .uart_rxd(uart_rxd),
-        .uart_txd(uart_txd)
-    );
+    generate
+        if (sc64::CPU_HAS_UART) begin
+            cpu_uart cpu_uart_inst (
+                .sys(sys),
+                .bus(bus.at[sc64::ID_CPU_UART].device),
+                .uart_rxd(uart_rxd),
+                .uart_txd(uart_txd)
+            );
+        end
+    endgenerate
 
     cpu_dma cpu_dma_inst (
         .sys(sys),

fw/rtl/system/sc64.sv

@@ -34,6 +34,8 @@ package sc64;
 
     parameter int CLOCK_FREQUENCY   = 32'd100_000_000;
 
+    parameter bit CPU_HAS_UART      = 1'b0;
+
     parameter int UART_BAUD_RATE    = 32'd1_000_000;
 
 endpackage

sw/riscv/src/dma.c

@@ -19,8 +19,3 @@ void dma_stop (void) {
 void dma_init (void) {
     dma_stop();
 }
-
-
-void process_dma (void) {
-
-}

sw/riscv/src/dma.h

@@ -20,7 +20,6 @@ bool dma_busy (void);
 void dma_start (uint32_t memory_address, size_t length, enum dma_id id, enum dma_dir dir);
 void dma_stop (void);
 void dma_init (void);
-void process_dma (void);
 
 
 #endif

sw/riscv/src/flashram.c

@@ -14,6 +14,17 @@ enum operation {
 };
 
 
+struct process {
+    bool save_in_progress;
+    enum operation op;
+    io32_t *save_pointer;
+    uint32_t num_words;
+    uint32_t current_word;
+};
+
+static struct process p;
+
+
 static enum operation get_operation_type (void) {
     uint32_t scr = FLASHRAM->SCR;
 
@@ -44,26 +55,38 @@ static size_t get_operation_length (enum operation op) {
 
 void flashram_init (void) {
     FLASHRAM->SCR = FLASHRAM_OPERATION_DONE;
+
+    p.save_in_progress = false;
 }
 
 
 void process_flashram (void) {
-    enum operation op = get_operation_type();
-    size_t length;
-    io32_t *save_data;
+    if (!p.save_in_progress) {
+        p.op = get_operation_type();
 
-    if (op != OP_NONE) {
-        length = get_operation_length(op);
-        save_data = (io32_t *) (SDRAM_BASE + CFG->SAVE_OFFSET + ((FLASHRAM->SCR >> FLASHRAM_PAGE_BIT) * FLASHRAM_PAGE_SIZE));
+        if (p.op != OP_NONE) {
+            uint32_t sdram_address = SDRAM_BASE + CFG->SAVE_OFFSET;
 
-        for (uint32_t i = 0; i < (length / 4); i++) {
-            if (op == OP_WRITE_PAGE) {
-                *save_data++ &= FLASHRAM->BUFFER[i];       
-            } else {
-                *save_data++ = FLASHRAM_ERASE_VALUE;
+            p.save_in_progress = true;
+            if (p.op != OP_ERASE_ALL) {
+                sdram_address += (FLASHRAM->SCR >> FLASHRAM_PAGE_BIT) * FLASHRAM_PAGE_SIZE;
             }
+            p.save_pointer = (io32_t *) (sdram_address);
+            p.num_words = get_operation_length(p.op) / sizeof(uint32_t);
+            p.current_word = 0;
+        }
+    } else {
+        if (p.op == OP_WRITE_PAGE) {
+            *p.save_pointer++ &= FLASHRAM->BUFFER[p.current_word];
+        } else {
+            *p.save_pointer++ = FLASHRAM_ERASE_VALUE;
         }
 
-        FLASHRAM->SCR = FLASHRAM_OPERATION_DONE;
+        p.current_word += 1;
+
+        if (p.current_word >= p.num_words) {
+            p.save_in_progress = false;
+            FLASHRAM->SCR = FLASHRAM_OPERATION_DONE;
+        }
     }
 }

sw/riscv/src/process.c

@@ -9,7 +9,20 @@
 #include "uart.h"
 
 
-void process_init (void) {
+static const void (*process_table[])(void) = {
+    process_usb,
+    process_cfg,
+    process_rtc,
+    process_i2c,
+    process_flashram,
+    process_uart,
+    NULL,
+};
+
+
+__attribute__((naked)) void process_loop (void) {
+    void (**process_func)(void) = process_table;
+
     usb_init();
     cfg_init();
     dma_init();
@@ -18,18 +31,12 @@ void process_init (void) {
     i2c_init();
     flashram_init();
     uart_init();
-}
 
-
-void process_loop (void) {
     while (1) {
-        process_usb();
-        process_cfg();
-        process_dma();
         process_joybus();
-        process_rtc();
-        process_i2c();
-        process_flashram();
-        process_uart();
+        (*process_func++)();
+        if (*process_func == NULL) {
+            process_func = process_table;
+        }
     }
 }

sw/riscv/src/startup.S

@@ -32,12 +32,9 @@ init_bss:
     blt a0, a1, 1b
 2:
 
-run:
-    call process_init
-    call process_loop
-
-loop:
-    j loop
+run_in_ram:
+    la ra, process_loop
+    jalr zero, 0(ra)
 
 copy_section:
     bge a1, a2, 2f

sw/riscv/src/sys.h

@@ -185,8 +185,4 @@ typedef volatile struct joybus_regs {
 #define JOYBUS_SCR_TX_LENGTH_BIT    (16)
 
 
-void reset_handler (void);
-void app_handler (void);
-
-
 #endif