Move bootloader reset signal detection to Wirish.

Use usb_cdcacm hooks to move the DTR edge and "1EAF" magic packet
detection to usb_serial.cpp. We'll later be able to extend this system
to support Leonardo-style reset signalling.

Signed-off-by: Marti Bolivar <mbolivar@leaflabs.com>

3 files changed, 140 insertions, 127 deletions

diff --git a/libmaple/include/libmaple/libmaple.h b/libmaple/include/libmaple/libmaple.h
index f1a595e..5abcaf9 100644
--- a/libmaple/include/libmaple/libmaple.h
+++ b/libmaple/include/libmaple/libmaple.h
@@ -48,7 +48,6 @@ extern "C" {
  */
 #define USER_ADDR_ROM 0x08005000
 #define USER_ADDR_RAM 0x20000C00
-#define STACK_TOP     0x20000800
 
 #ifdef __cplusplus
 }
diff --git a/libmaple/usb/stm32f1/usb_cdcacm.c b/libmaple/usb/stm32f1/usb_cdcacm.c
index 44b2239..7a7d656 100644
--- a/libmaple/usb/stm32f1/usb_cdcacm.c
+++ b/libmaple/usb/stm32f1/usb_cdcacm.c
@@ -82,8 +82,6 @@ static uint8* usbGetStringDescriptor(uint16 length);
 static void usbSetConfiguration(void);
 static void usbSetDeviceAddress(void);
 
-static void wait_reset(void);
-
 /*
  * Descriptors
  */
@@ -263,13 +261,6 @@ ONE_DESCRIPTOR String_Descriptor[3] = {
  * Etc.
  */
 
-typedef enum {
-  DTR_UNSET,
-  DTR_HIGH,
-  DTR_NEGEDGE,
-  DTR_LOW
-} RESET_STATE;
-
 typedef struct {
   uint32 bitrate;
   uint8  format;
@@ -284,7 +275,6 @@ USB_Line_Coding line_coding = {
     .paritytype = 0x00,
     .datatype = 0x08
 };
-RESET_STATE reset_state = DTR_UNSET;
 
 static volatile uint8 vcomBufferRx[USB_CDCACM_RX_BUFLEN];
 static volatile uint32 rx_offset = 0;
@@ -492,64 +482,13 @@ static void vcomDataTxCb(void) {
     countTx = 0;
 }
 
-#define EXC_RETURN 0xFFFFFFF9
-#define DEFAULT_CPSR 0x61000000
 static void vcomDataRxCb(void) {
-    /* FIXME this is mad buggy */
-
     /* This following is safe since sizeof(vcomBufferRx) exceeds the
      * largest possible USB_CDCACM_RX_EPSIZE, and we set to NAK after
      * each data packet. Only when all bytes have been read is the RX
      * endpoint set back to VALID. */
     newBytes = usb_get_ep_rx_count(USB_CDCACM_RX_ENDP);
     usb_set_ep_rx_stat(USB_CDCACM_RX_ENDP, USB_EP_STAT_RX_NAK);
-
-    /* magic number, {0x31, 0x45, 0x41, 0x46} is "1EAF" */
-    uint8 chkBuf[4];
-    uint8 cmpBuf[4] = {0x31, 0x45, 0x41, 0x46};
-    if (reset_state == DTR_NEGEDGE) {
-        reset_state = DTR_LOW;
-
-        if  (newBytes >= 4) {
-            unsigned int target = (unsigned int)wait_reset | 0x1;
-
-            usb_copy_from_pma(chkBuf, 4, USB_CDCACM_RX_ADDR);
-
-            int i;
-            USB_Bool cmpMatch = TRUE;
-            for (i = 0; i < 4; i++) {
-                if (chkBuf[i] != cmpBuf[i]) {
-                    cmpMatch = FALSE;
-                }
-            }
-
-            if (cmpMatch) {
-                asm volatile("mov r0, %[stack_top]      \n\t" // Reset stack
-                             "mov sp, r0                \n\t"
-                             "mov r0, #1                \n\t"
-                             "mov r1, %[target_addr]    \n\t"
-                             "mov r2, %[cpsr]           \n\t"
-                             "push {r2}                 \n\t" // Fake xPSR
-                             "push {r1}                 \n\t" // PC target addr
-                             "push {r0}                 \n\t" // Fake LR
-                             "push {r0}                 \n\t" // Fake R12
-                             "push {r0}                 \n\t" // Fake R3
-                             "push {r0}                 \n\t" // Fake R2
-                             "push {r0}                 \n\t" // Fake R1
-                             "push {r0}                 \n\t" // Fake R0
-                             "mov lr, %[exc_return]     \n\t"
-                             "bx lr"
-                             :
-                             : [stack_top] "r" (STACK_TOP),
-                               [target_addr] "r" (target),
-                               [exc_return] "r" (EXC_RETURN),
-                               [cpsr] "r" (DEFAULT_CPSR)
-                             : "r0", "r1", "r2");
-                /* should never get here */
-            }
-        }
-    }
-
     usb_copy_from_pma((uint8*)vcomBufferRx, newBytes, USB_CDCACM_RX_ADDR);
 
     if (rx_hook) {
@@ -634,28 +573,27 @@ static void usbReset(void) {
 }
 
 static RESULT usbDataSetup(uint8 request) {
-    uint8 *(*CopyRoutine)(uint16);
-    CopyRoutine = NULL;
+    uint8* (*CopyRoutine)(uint16) = 0;
 
     if (Type_Recipient == (CLASS_REQUEST | INTERFACE_RECIPIENT)) {
-        /* Call the user hook first. */
-        if (iface_setup_hook) {
-            uint8 req_copy = request;
-            iface_setup_hook(USB_CDCACM_HOOK_IFACE_SETUP, &req_copy);
-        }
-
         switch (request) {
-        case (USB_CDCACM_GET_LINE_CODING):
+        case USB_CDCACM_GET_LINE_CODING:
             CopyRoutine = vcomGetSetLineCoding;
             last_request = USB_CDCACM_GET_LINE_CODING;
             break;
-        case (USB_CDCACM_SET_LINE_CODING):
+        case USB_CDCACM_SET_LINE_CODING:
             CopyRoutine = vcomGetSetLineCoding;
             last_request = USB_CDCACM_SET_LINE_CODING;
             break;
         default:
             break;
         }
+
+        /* Call the user hook. */
+        if (iface_setup_hook) {
+            uint8 req_copy = request;
+            iface_setup_hook(USB_CDCACM_HOOK_IFACE_SETUP, &req_copy);
+        }
     }
 
     if (CopyRoutine == NULL) {
@@ -669,66 +607,32 @@ static RESULT usbDataSetup(uint8 request) {
 }
 
 static RESULT usbNoDataSetup(uint8 request) {
+    RESULT ret = USB_UNSUPPORT;
     uint8 new_signal;
 
-    /* we support set com feature but dont handle it */
     if (Type_Recipient == (CLASS_REQUEST | INTERFACE_RECIPIENT)) {
-        /* Call the user hook first. */
-        if (iface_setup_hook) {
-            uint8 req_copy = request;
-            iface_setup_hook(USB_CDCACM_HOOK_IFACE_SETUP, &req_copy);
-        }
-
         switch (request) {
-        case (USB_CDCACM_SET_COMM_FEATURE):
-            return USB_SUCCESS;
-        case (USB_CDCACM_SET_CONTROL_LINE_STATE):
-            /* to reset the board, pull both dtr and rts low
-               then pulse dtr by itself */
+        case USB_CDCACM_SET_COMM_FEATURE:
+            /* We support set comm. feature, but don't handle it. */
+            ret = USB_SUCCESS;
+            break;
+        case USB_CDCACM_SET_CONTROL_LINE_STATE:
+            /* Track changes to DTR and RTS. */
             new_signal = (pInformation->USBwValues.bw.bb0 &
                           (USB_CDCACM_CONTROL_LINE_DTR |
                            USB_CDCACM_CONTROL_LINE_RTS));
             line_dtr_rts = new_signal & 0x03;
+            ret = USB_SUCCESS;
+            break;
+        }
 
-            switch (reset_state) {
-                /* no default, covered enum */
-            case DTR_UNSET:
-                if ((new_signal & USB_CDCACM_CONTROL_LINE_DTR) == 0 ) {
-                    reset_state = DTR_LOW;
-                } else {
-                    reset_state = DTR_HIGH;
-                }
-                break;
-
-            case DTR_HIGH:
-                if ((new_signal & USB_CDCACM_CONTROL_LINE_DTR) == 0 ) {
-                    reset_state = DTR_NEGEDGE;
-                } else {
-                    reset_state = DTR_HIGH;
-                }
-                break;
-
-            case DTR_NEGEDGE:
-                if ((new_signal & USB_CDCACM_CONTROL_LINE_DTR) == 0 ) {
-                    reset_state = DTR_LOW;
-                } else {
-                    reset_state = DTR_HIGH;
-                }
-                break;
-
-            case DTR_LOW:
-                if ((new_signal & USB_CDCACM_CONTROL_LINE_DTR) == 0 ) {
-                    reset_state = DTR_LOW;
-                } else {
-                    reset_state = DTR_HIGH;
-                }
-                break;
-            }
-
-            return USB_SUCCESS;
+        /* Call the user hook. */
+        if (iface_setup_hook) {
+            uint8 req_copy = request;
+            iface_setup_hook(USB_CDCACM_HOOK_IFACE_SETUP, &req_copy);
         }
     }
-    return USB_UNSUPPORT;
+    return ret;
 }
 
 static RESULT usbGetInterfaceSetting(uint8 interface, uint8 alt_setting) {
@@ -767,9 +671,3 @@ static void usbSetConfiguration(void) {
 static void usbSetDeviceAddress(void) {
     USBLIB->state = USB_ADDRESSED;
 }
-
-#define RESET_DELAY                     100000
-static void wait_reset(void) {
-  delay_us(RESET_DELAY);
-  nvic_sys_reset();
-}
diff --git a/wirish/usb_serial.cpp b/wirish/usb_serial.cpp
index cfc6317..bf2ea4e 100644
--- a/wirish/usb_serial.cpp
+++ b/wirish/usb_serial.cpp
@@ -32,11 +32,23 @@
 
 #include <string.h>
 
+#include <libmaple/nvic.h>
 #include <libmaple/usb_cdcacm.h>
 #include <libmaple/usb.h>
 
 #include <wirish/wirish.h>
 
+/*
+ * Hooks used for bootloader reset signalling
+ */
+
+static void rxHook(unsigned, void*);
+static void ifaceSetupHook(unsigned, void*);
+
+/*
+ * USBSerial interface
+ */
+
 #define USB_TIMEOUT 50
 
 USBSerial::USBSerial(void) {
@@ -48,12 +60,15 @@ USBSerial::USBSerial(void) {
 void USBSerial::begin(void) {
 #if BOARD_HAVE_SERIALUSB
     usb_cdcacm_enable(BOARD_USB_DISC_DEV, BOARD_USB_DISC_BIT);
+    usb_cdcacm_set_hooks(USB_CDCACM_HOOK_RX, rxHook);
+    usb_cdcacm_set_hooks(USB_CDCACM_HOOK_IFACE_SETUP, ifaceSetupHook);
 #endif
 }
 
 void USBSerial::end(void) {
 #if BOARD_HAVE_SERIALUSB
     usb_cdcacm_disable(BOARD_USB_DISC_DEV, BOARD_USB_DISC_BIT);
+    usb_cdcacm_remove_hooks(USB_CDCACM_HOOK_RX | USB_CDCACM_HOOK_IFACE_SETUP);
 #endif
 }
 
@@ -126,3 +141,104 @@ uint8 USBSerial::getRTS(void) {
 #if BOARD_HAVE_SERIALUSB
 USBSerial SerialUSB;
 #endif
+
+/*
+ * Bootloader hook implementations
+ */
+
+enum reset_state_t {
+    DTR_UNSET,
+    DTR_HIGH,
+    DTR_NEGEDGE,
+    DTR_LOW
+};
+
+static reset_state_t reset_state = DTR_UNSET;
+
+static void ifaceSetupHook(unsigned hook, void *requestvp) {
+    uint8 request = *(uint8*)requestvp;
+
+    // Ignore requests we're not interested in.
+    if (request != USB_CDCACM_SET_CONTROL_LINE_STATE) {
+        return;
+    }
+
+    // We need to see a negative edge on DTR before we start looking
+    // for the in-band magic reset byte sequence.
+    uint8 dtr = usb_cdcacm_get_dtr();
+    switch (reset_state) {
+    case DTR_UNSET:
+        reset_state = dtr ? DTR_HIGH : DTR_LOW;
+        break;
+    case DTR_HIGH:
+        reset_state = dtr ? DTR_HIGH : DTR_NEGEDGE;
+        break;
+    case DTR_NEGEDGE:
+        reset_state = dtr ? DTR_HIGH : DTR_LOW;
+        break;
+    case DTR_LOW:
+        reset_state = dtr ? DTR_HIGH : DTR_LOW;
+        break;
+    }
+}
+
+#define RESET_DELAY 100000
+static void wait_reset(void) {
+  delay_us(RESET_DELAY);
+  nvic_sys_reset();
+}
+
+#define STACK_TOP 0x20000800
+#define EXC_RETURN 0xFFFFFFF9
+#define DEFAULT_CPSR 0x61000000
+static void rxHook(unsigned hook, void *ignored) {
+    /* FIXME this is mad buggy; we need a new reset sequence. E.g. NAK
+     * after each RX means you can't reset if any bytes are waiting. */
+    if (reset_state == DTR_NEGEDGE) {
+        reset_state = DTR_LOW;
+
+        if (usb_cdcacm_data_available() >= 4) {
+            // The magic reset sequence is "1EAF".
+            uint8 cmpBuf[4] = {'1', 'E', 'A', 'F'};
+            uint8 chkBuf[4];
+
+            // Peek at the waiting bytes, looking for reset sequence.
+            usb_cdcacm_peek(chkBuf, 4);
+            bool cmpMatch = true;
+            for (int i = 0; i < 4; i++) {
+                if (chkBuf[i] != cmpBuf[i]) {
+                    cmpMatch = false;
+                    break;
+                }
+            }
+
+            // Got the magic sequence? Reset, presumably into the bootloader.
+            if (cmpMatch) {
+                // Return address is wait_reset, but we must set the thumb bit.
+                unsigned int target = (unsigned int)wait_reset | 0x1;
+                asm volatile("mov r0, %[stack_top]      \n\t" // Reset stack
+                             "mov sp, r0                \n\t"
+                             "mov r0, #1                \n\t"
+                             "mov r1, %[target_addr]    \n\t"
+                             "mov r2, %[cpsr]           \n\t"
+                             "push {r2}                 \n\t" // Fake xPSR
+                             "push {r1}                 \n\t" // PC target addr
+                             "push {r0}                 \n\t" // Fake LR
+                             "push {r0}                 \n\t" // Fake R12
+                             "push {r0}                 \n\t" // Fake R3
+                             "push {r0}                 \n\t" // Fake R2
+                             "push {r0}                 \n\t" // Fake R1
+                             "push {r0}                 \n\t" // Fake R0
+                             "mov lr, %[exc_return]     \n\t"
+                             "bx lr"
+                             :
+                             : [stack_top] "r" (STACK_TOP),
+                               [target_addr] "r" (target),
+                               [exc_return] "r" (EXC_RETURN),
+                               [cpsr] "r" (DEFAULT_CPSR)
+                             : "r0", "r1", "r2");
+                /* should never get here */
+            }
+        }
+    }
+}