Blackfin: dynamically update UART speed when initializing

Previously, booting over the UART required the baud rate to be known ahead
of time.  Using a bit of tricky simple math, we can calculate the new board
rate based on the old divisors.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Robin Getz <rgetz@blackfin.uclinux.org>

cpu/blackfin/initcode.c

@@ -20,7 +20,7 @@
 #include "serial.h"
 
 __attribute__((always_inline))
-static inline uint32_t serial_init(void)
+static inline void serial_init(void)
 {
 #ifdef __ADSPBF54x__
 # ifdef BFIN_BOOT_UART_USE_RTS
@@ -61,25 +61,16 @@ static inline uint32_t serial_init(void)
 	}
 #endif
 
-	uint32_t old_baud;
-	if (BFIN_DEBUG_EARLY_SERIAL || CONFIG_BFIN_BOOT_MODE == BFIN_BOOT_UART)
-		old_baud = serial_early_get_baud();
-	else
-		old_baud = CONFIG_BAUDRATE;
-
 	if (BFIN_DEBUG_EARLY_SERIAL) {
+		int ucen = *pUART_GCTL & UCEN;
 		serial_early_init();
 
 		/* If the UART is off, that means we need to program
 		 * the baud rate ourselves initially.
 		 */
-		if (!old_baud) {
-			old_baud = CONFIG_BAUDRATE;
+		if (ucen != UCEN)
 			serial_early_set_baud(CONFIG_BAUDRATE);
-		}
 	}
-
-	return old_baud;
 }
 
 __attribute__((always_inline))
@@ -93,30 +84,6 @@ static inline void serial_deinit(void)
 #endif
 }
 
-/* We need to reset the baud rate when we have early debug turned on
- * or when we are booting over the UART.
- * XXX: we should fix this to calc the old baud and restore it rather
- *      than hardcoding it via CONFIG_LDR_LOAD_BAUD ... but we have
- *      to figure out how to avoid the division in the baud calc ...
- */
-__attribute__((always_inline))
-static inline void serial_reset_baud(uint32_t baud)
-{
-	if (!BFIN_DEBUG_EARLY_SERIAL && CONFIG_BFIN_BOOT_MODE != BFIN_BOOT_UART)
-		return;
-
-#ifndef CONFIG_LDR_LOAD_BAUD
-# define CONFIG_LDR_LOAD_BAUD 115200
-#endif
-
-	if (CONFIG_BFIN_BOOT_MODE == BFIN_BOOT_BYPASS)
-		serial_early_set_baud(baud);
-	else if (CONFIG_BFIN_BOOT_MODE == BFIN_BOOT_UART)
-		serial_early_set_baud(CONFIG_LDR_LOAD_BAUD);
-	else
-		serial_early_set_baud(CONFIG_BAUDRATE);
-}
-
 __attribute__((always_inline))
 static inline void serial_putc(char c)
 {
@@ -239,7 +206,14 @@ static inline void serial_putc(char c)
 BOOTROM_CALLED_FUNC_ATTR
 void initcode(ADI_BOOT_DATA *bootstruct)
 {
-	uint32_t old_baud = serial_init();
+	/* Save the clock pieces that are used in baud rate calculation */
+	unsigned int sdivB, divB, vcoB;
+	serial_init();
+	if (BFIN_DEBUG_EARLY_SERIAL || CONFIG_BFIN_BOOT_MODE == BFIN_BOOT_UART) {
+		sdivB = bfin_read_PLL_DIV() & 0xf;
+		vcoB = (bfin_read_PLL_CTL() >> 9) & 0x3f;
+		divB = serial_early_get_div();
+	}
 
 #ifdef CONFIG_HW_WATCHDOG
 # ifndef CONFIG_HW_WATCHDOG_TIMEOUT_INITCODE
@@ -334,8 +308,20 @@ void initcode(ADI_BOOT_DATA *bootstruct)
 
 	/* Since we've changed the SCLK above, we may need to update
 	 * the UART divisors (UART baud rates are based on SCLK).
+	 * Do the division by hand as there are no native instructions
+	 * for dividing which means we'd generate a libgcc reference.
 	 */
-	serial_reset_baud(old_baud);
+	if (CONFIG_BFIN_BOOT_MODE == BFIN_BOOT_UART) {
+		unsigned int sdivR, vcoR;
+		sdivR = bfin_read_PLL_DIV() & 0xf;
+		vcoR = (bfin_read_PLL_CTL() >> 9) & 0x3f;
+		int dividend = sdivB * divB * vcoR;
+		int divisor = vcoB * sdivR;
+		unsigned int quotient;
+		for (quotient = 0; dividend > 0; ++quotient)
+			dividend -= divisor;
+		serial_early_put_div(quotient - ANOMALY_05000230);
+	}
 
 	serial_putc('F');
 

cpu/blackfin/serial.h

@@ -156,16 +156,25 @@ static inline void serial_early_init(void)
 }
 
 __attribute__((always_inline))
-static inline uint32_t serial_early_get_baud(void)
+static inline void serial_early_put_div(uint16_t divisor)
 {
-	/* If the UART isnt enabled, then we are booting an LDR
-	 * from a non-UART source (so like flash) which means
-	 * the baud rate here is meaningless.
-	 */
-	if ((*pUART_GCTL & UCEN) != UCEN)
-		return 0;
+	/* Set DLAB in LCR to Access DLL and DLH */
+	ACCESS_LATCH();
+	SSYNC();
 
-#if (0)	/* See comment for serial_reset_baud() in initcode.c */
+	/* Program the divisor to get the baud rate we want */
+	*pUART_DLL = LOB(divisor);
+	*pUART_DLH = HIB(divisor);
+	SSYNC();
+
+	/* Clear DLAB in LCR to Access THR RBR IER */
+	ACCESS_PORT_IER();
+	SSYNC();
+}
+
+__attribute__((always_inline))
+static inline uint16_t serial_early_get_div(void)
+{
 	/* Set DLAB in LCR to Access DLL and DLH */
 	ACCESS_LATCH();
 	SSYNC();
@@ -173,16 +182,12 @@ static inline uint32_t serial_early_get_baud(void)
 	uint8_t dll = *pUART_DLL;
 	uint8_t dlh = *pUART_DLH;
 	uint16_t divisor = (dlh << 8) | dll;
-	uint32_t baud = get_sclk() / (divisor * 16);
 
 	/* Clear DLAB in LCR to Access THR RBR IER */
 	ACCESS_PORT_IER();
 	SSYNC();
 
-	return baud;
-#else
-	return CONFIG_BAUDRATE;
-#endif
+	return divisor;
 }
 
 __attribute__((always_inline))
@@ -192,20 +197,7 @@ static inline void serial_early_set_baud(uint32_t baud)
 	 * weird multiplication is to make sure we over sample just
 	 * a little rather than under sample the incoming signals.
 	 */
-	uint16_t divisor = (get_sclk() + (baud * 8)) / (baud * 16) - ANOMALY_05000230;
-
-	/* Set DLAB in LCR to Access DLL and DLH */
-	ACCESS_LATCH();
-	SSYNC();
-
-	/* Program the divisor to get the baud rate we want */
-	*pUART_DLL = LOB(divisor);
-	*pUART_DLH = HIB(divisor);
-	SSYNC();
-
-	/* Clear DLAB in LCR to Access THR RBR IER */
-	ACCESS_PORT_IER();
-	SSYNC();
+	serial_early_put_div((get_sclk() + (baud * 8)) / (baud * 16) - ANOMALY_05000230);
 }
 
 #ifndef BFIN_IN_INITCODE
@@ -235,32 +227,6 @@ static inline void serial_early_puts(const char *s)
 #endif
 .endm
 
-/* Recursively expand calls to _serial_putc for every byte
- * passed to us.  Append a newline when we're all done.
- */
-.macro _serial_early_putc byte:req morebytes:vararg
-#ifdef CONFIG_DEBUG_EARLY_SERIAL
-	R0 = \byte;
-	call _serial_putc;
-.ifnb \morebytes
-	_serial_early_putc \morebytes
-.else
-.if (\byte != '\n')
-	_serial_early_putc '\n'
-.endif
-.endif
-#endif
-.endm
-
-/* Wrapper around recurisve _serial_early_putc macro which
- * simply prepends the string "Early: "
- */
-.macro serial_early_putc byte:req morebytes:vararg
-#ifdef CONFIG_DEBUG_EARLY_SERIAL
-	_serial_early_putc 'E', 'a', 'r', 'l', 'y', ':', ' ', \byte, \morebytes
-#endif
-.endm
-
 /* Since we embed the string right into our .text section, we need
  * to find its address.  We do this by getting our PC and adding 2
  * bytes (which is the length of the jump instruction).  Then we