iokbd keysc: space optimizations for SH3

* Reduce the keyboard queue size from 64 to 32, which is more than
  enough even for real-time games with multiple key presses.
* Pack the driver_event_t structure of the keyboard driver to make it 4
  bytes rather than 6 bytes. Combined with the previous item, this saves
  256 bytes off the BSS section (which is 3% of the SH3's static RAM).
* As part of a debugging attempt, updated the watchdog delay code in
  iokbd_delay() to make it usable in the current version of gint.
* Restored port registers more aggressively in iokbd_row().

include/gint/keyboard.h

@@ -117,12 +117,12 @@ enum
 /* Size of the buffer event queue, can be customized using gint's configure
    script before compiling the library. Better be a power of 2. */
 #ifndef KEYBOARD_QUEUE_SIZE
-#define KEYBOARD_QUEUE_SIZE 64
+#define KEYBOARD_QUEUE_SIZE 32
 #endif
 
 /* Keyboard frequency analysis, must be at least 64 for the keyboard to work,
    and at most 32768 for the extra timer to support it. Better if a power of 2.
-   TODO: Add a configure or runtime setting for KEYBOARD_SCAN_FREQUENCY */
+   TODO: Add a runtime setting for KEYBOARD_SCAN_FREQUENCY */
 #ifndef KEYBOARD_SCAN_FREQUENCY
 #define KEYBOARD_SCAN_FREQUENCY 128
 #endif

src/core/mmu.c

@@ -25,7 +25,7 @@ GINLINE const tlb_data_t *tlb_data(uint way, uint E)
 	return (void *)addr;
 }
 
-/* tlb_mapped_memort() - count amount of mapped memory */
+/* tlb_mapped_memory() - count amount of mapped memory */
 void tlb_mapped_memory(uint32_t *p_rom, uint32_t *p_ram)
 {
 	uint32_t rom = 0, ram = 0;

src/keysc/iokbd.c

@@ -21,26 +21,30 @@ static void iokbd_delay(void)
 	);
 
 #if 0
-	/* Watchdog delay version */
+	uint8_t  volatile *WTCSRr = (void *)0xffffff86;
+	uint16_t volatile *WTCSRw = (void *)0xffffff86;
+	uint16_t volatile *WTCNTw = (void *)0xffffff84;
+
+	/* Watchdog delay version, each of the values between this and 0xff
+	   account for 256 clock cycles on Pphi. This is roughly equivalent to
+	   2048 nop, lasting ~70 µs */
 	const int delay = 0xf4;
 
 	/* Disable the watchdog timer interrupt and reset configuration */
-	INTC.IPRB.BIT._WDT = 0;
+	*WTCSRw = 0xa500;
-	WDT.WTCSR.WRITE = 0xa500;
 
 	/* Set the delay, input on Pphi / 256 and start counting */
-	WDT.WTCNT.WRITE = 0x5a00 | (delay & 0xff);
+	*WTCNTw = 0x5a00 | (delay & 0xff);
-	WDT.WTCSR.WRITE = 0xa505;
+	*WTCSRw = 0xa505;
-	WDT.WTCSR.WRITE = 0xa585;
+	*WTCSRw = 0xa585;
 
 	/* Actively wait for overflow, then clear the interrupt flag */
-	while((WDT.WTCSR.READ.BYTE & 0x08) == 0);
+	while((*WTCSRr & 0x08) == 0);
-	WDT.WTCSR.WRITE = 0xa500 | (WDT.WTCSR.READ.BYTE & 0xf7);
+	*WTCSRw = 0xa500 | (*WTCSRr & 0xf7);
 
 	/* Reset configuration, counter, and re-enabled interrupt */
-	WDT.WTCSR.WRITE = 0xa500;
+	*WTCSRw = 0xa500;
-	WDT.WTCSR.WRITE = 0x5a00;
+	*WTCNTw = 0x5a00;
-	INTC.IPRB.BIT._WDT = GINT_INTP_WDT;
 #endif
 }
 
@@ -52,6 +56,11 @@ uint8_t iokbd_row(int row)
 	if((unsigned)row > 9) return 0x00;
 	row ^= 1;
 
+	int orig_PBCR = PFC.PBCR;
+	int orig_PMCR = PFC.PMCR;
+	int orig_PBDR = PFC.PBDR;
+	int orig_PMDR = PFC.PMDR;
+
 	/* This will enable output (01) on @row, input (10) everywhere else */
 	uint16_t ctrl_mask = 0x0003 << ((row & 7) * 2);
 	/* Enable output (0) on @row, input (1) everywhere else */
@@ -81,25 +90,23 @@ uint8_t iokbd_row(int row)
 		/* Set @row to 0, everything else to 1 */
 		PFC.PBDR = 0xff;
 		PFC.PMDR = PFC.PMDR & data_mask;
+		iokbd_delay();
 	}
 
 	/* Now read the input data from the keyboard! */
 	uint8_t input = ~PFC.PADR;
 	iokbd_delay();
 
-	/* Reset the port configuration. I don't know why the intermediate step
+	/* Reset the port configuration */
-	   is necessary; refer to SimLo's documentation. */
+	PFC.PBCR = orig_PBCR;
-	PFC.PBCR = 0xaaaa;
+	PFC.PMCR = orig_PMCR;
-	PFC.PMCR = (PFC.PMCR & 0xff00) | 0x00aa;
-	iokbd_delay();
-	PFC.PBCR = 0x5555;
-	PFC.PMCR = (PFC.PMCR & 0xff00) | 0x0055;
 	iokbd_delay();
 
 	/* Now also reset the data registers. This was forgotten from SimLo's
 	   CheckKeyRow() and blows up everything. */
-	PFC.PBDR = 0x00;
+	PFC.PBDR = orig_PBDR;
-	PFC.PMDR = PFC.PMDR & 0xf0;
+	PFC.PMDR = orig_PMDR;
+	iokbd_delay();
 
 	return input;
 }

src/keysc/keysc.c

@@ -38,9 +38,9 @@ GDATA static uint8_t current[12] = { 0 };
 typedef struct
 {
 	uint16_t time;    /* Locally unique time identifier */
-	uint8_t row;      /* Row number */
 	uint8_t changed;  /* Keys that changed state */
-	uint8_t kind;     /* Type of change, either KEYEV_DOWN or KEYEV_UP */
+	uint8_t row  :4;  /* Row number */
+	uint8_t kind :4;  /* Type of change, either KEYEV_DOWN or KEYEV_UP */
 
 } driver_event_t;
 
@@ -103,7 +103,7 @@ static void keysc_frame(void)
 		if(!diff) continue;
 
 		/* Update internal status if the event could be pushed */
-		driver_event_t ev = { time, row, diff, KEYEV_UP };
+		driver_event_t ev = { time, diff, row, KEYEV_UP };
 		if(!buffer_push(ev)) state[row] &= scan[row];
 	}
 	for(int row = 0; row < 12; row++)
@@ -111,7 +111,7 @@ static void keysc_frame(void)
 		int diff = scan[row] & ~state[row];
 		if(!diff) continue;
 
-		driver_event_t ev = { time, row, diff, KEYEV_DOWN };
+		driver_event_t ev = { time, diff, row, KEYEV_DOWN };
 		if(!buffer_push(ev)) state[row] |= scan[row];
 	}
 }