fw/boot/ - The boot loader, fresh from IDBG. Needs major cleanup.

fw/boot/boot.c

@@ -0,0 +1,243 @@
+/*
+ * boot/boot.c - Boot loader setup and main loop
+ *
+ * Written 2008, 2010 by Werner Almesberger
+ * Copyright 2008, 2010 Werner Almesberger
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+/*
+ * This code follows the register read/write sequences from the examples in
+ * SiLabs/MCU/Examples/C8051F326_7/USB_Interrupt/Firmware/F326_USB_Main.c and 
+ * SiLabs/MCU/Examples/C8051F326_7/USB_Interrupt/Firmware/F326_USB_ISR.c
+ */
+
+
+#include <stdint.h>
+
+#include "version.h"
+#include "regs.h"
+#include "io.h"
+#include "uart.h"
+#include "usb.h"
+#include "dfu.h"
+
+
+void run_payload(void)
+{
+	/* No interrupts while jumping between worlds */
+	EA = 0;
+
+	/* Restart USB */
+	USB0XCN = 0;
+
+	/* Re-enable pull-ups */
+	GPIOCN &= ~WEAKPUD;
+
+#ifdef GTA
+	/* Don't waste power in pull-down */
+	I2C_SDA_PULL = 1;
+#endif
+
+	debug("launching payload\n");
+
+	__asm
+	ljmp	PAYLOAD_START
+	__endasm;
+}
+
+
+/* ----- Interrupts -------------------------------------------------------- */
+
+
+/*
+ * The boot loader doesn't use interrupts, so we forward all interrupts to the
+ * payload.
+ *
+ * What we'd really like to do here is to say something like
+ *
+ * void whatever_isr(void) __interrupt(n) __at(PAYLOAD+n*8+1);
+ *
+ * However, sdcc doesn't support such things yet. So we declare the ISR such
+ * that the vector entry gets created, and then we tell the assembler where to
+ * find it.
+ *
+ * Since __asm/__endasm isn't allowed outside a function body, we generate a
+ * dummy function for each assignment. The function is "naked", so that no
+ * actual code is generated for it.
+ */
+
+#define	ISR(n) \
+	void isr_nr_##n(void) __interrupt(n); \
+	void isr_dummy_##n(void) __naked \
+	{ \
+		__asm \
+		_isr_nr_##n = PAYLOAD_START+n*8+3 \
+		__endasm; \
+	}
+
+
+ISR(0)
+ISR(1)
+ISR(2)
+ISR(3)
+ISR(4)
+ISR(8)
+ISR(15)
+
+
+/* ----- The actual boot loader -------------------------------------------- */
+
+
+static void delay(void)
+{
+	int x;
+
+	for (x = 0; x < 500; x)
+		x++;
+}
+
+
+static void boot_loader(void)
+{
+	/*
+	 * If we have VBUS, proceed as follows:
+	 * - bring up USB
+	 * - try to contact the PMU (in a loop)
+	 * - possible transitions:
+	 *   - DFU gets selected -> enter DFU mode
+	 *   - PMU responds -> jump to payload
+	 *
+	 * In DFU mode, the following transitions are possible:
+	 * - VBUS drops -> reset
+	 * - USB bus reset -> reset
+	 *
+	 * @@@ this may be too complex - probably don't really need to talk to
+	 * the PMU.
+	 */
+
+	/*
+	 * Note: if we do anything that delays CPU bringup after nRESET goes
+	 * high, we must still stay in the 100ms budget for raising KEEPACT.
+	 */
+
+	OSCICN |= IFCN0 | IFCN1;
+
+#ifdef LOW_SPEED
+
+	CLKSEL = 0x10;	/* USBCLK = int/2, SYS_INT_OSC = int */
+
+#else /* LOW_SPEED */
+
+	/*
+	 * Clock multiplier enable sequence, section 10.4
+	 *
+	 * - reset the multiplier
+	 * - select the multiplier input source
+	 * - enable the multiplier
+	 * - delay for 5us
+	 * - initialize the multiplier
+	 * - poll for multiplier to be ready
+	 */
+
+	CLKMUL = 0;
+	CLKMUL |= MULEN;
+	delay();
+	CLKMUL |= MULINIT | MULEN;
+	while (!(CLKMUL & MULRDY));
+	CLKSEL = 0;	/* USBCLK = 4*int, SYSCLK = int */
+	CLKSEL = 0x02;	/* F326_USB_Main.c does this (sets 24MHz). Why ? */
+
+	uart_init(24);
+
+#endif /* !LOW_SPEED */
+
+	printk("%s #%u\n", build_date, build_number);
+
+	/*
+	 * Very weakly pull SDA down and disable all pull-ups.
+	 *
+	 * We use SDA as a system power presence detector. When I2C is idle,
+	 * SDA is kept high. This is accomplished with pull-ups in the system.
+	 * We can therefore detect if IO_3V3 is any good by checking whether
+	 * SDA is high.
+	 *
+	 * This should work even without our own pull-down. However, when the
+	 * IDBG board is operating standalone (or, generally, if SDA isn't
+	 * connected), SDA would float. We therefore have to pull it down a
+	 * little.
+	 */
+
+	/*
+	 * Ben variant:
+	 *
+	 * We use exactly the same logic as on GTA01/02, but with different
+	 * signals. P0_1 (I2C_SDA_PULL) and P0_2 (I2C_SDA) both connect to
+	 * +V3.3, with a 1 kOhm resistor on P0_1. If the Ben is not powered, we
+	 * can therefore pull +V3.3 to GND, and detect this condition. As on
+	 * the GTA01/02, once the system is powered up, IDBG exits this loop.
+	 */
+
+	GPIOCN |= WEAKPUD;
+#ifdef GTA
+	I2C_SDA_PULL = 0;
+#endif
+	delay();
+
+	dfu_init();
+	usb_init();
+
+#ifdef GTA
+
+	while (!I2C_SDA || dfu.state != dfuIDLE)
+		usb_poll();
+
+#else /* GTA */
+
+#define	MS_TO_LOOPS(ms)	((uint32_t) (ms)*190)
+
+	{
+		uint32_t loop = 0;
+
+		while (loop != MS_TO_LOOPS(2000)) {
+			usb_poll();
+			if (dfu.state == dfuIDLE)
+				loop++;
+			else
+				loop = 0;
+		}
+	}
+#endif /* !GTA */
+}
+
+
+void main(void)
+{
+	/*
+	 * VDD monitor enable sequence, section 7.2
+	 *
+	 * - enable voltage monitor
+	 * - wait for monitor to stabilize
+	 * - enable VDD monitor reset
+	 */
+
+	VDM0CN = VDMEN;
+	while (!(VDM0CN & VDDSTAT));
+	RSTSRC = PORSF;
+
+	/*
+	 * @@@ if we don't have VBUS, proceed as follows:
+	 * - stay at 3MHz (current < 2mA, so we're fine with GPIO power)
+	 * - jump directly to the payload
+	 */
+
+	OSCICN |= IFCN0;
+	uart_init(3);
+	if (REG0CN & VBSTAT)
+		boot_loader();
+	run_payload();
+}