Add error checking both before and after flashing

Before we start flashing then do a crc32 check on all payloads so if
the reloader hasn't been programmed correctly we don't proceed.

After flashing we check that what we wrote and retry if it doesn't
match.

Signed-off-by: Daniel Thompson <daniel@redfelineninja.org.uk>

src/flash.c

@@ -5,6 +5,8 @@
 
 #include "flash.h"
 
+#include <string.h>
+
 #include <nrfx_nvmc.h>
 #include <nrf_gpio.h>
 #include <nrf_wdt.h>
@@ -17,7 +19,7 @@ static int percent_complete;
 static uint32_t bytes_processed;
 static uint32_t total_bytes;
 
-static void progress(uint32_t nbytes)
+static void progress(int32_t nbytes)
 {
     bytes_processed += nbytes;
 
@@ -28,13 +30,40 @@ static void progress(uint32_t nbytes)
     }
 }
 
+/* slow but no table overhead ;-) */
+uint32_t crc32(const uint8_t *data, uint32_t len)
+{
+	uint32_t crc = 0xffffffff;
+
+	for (int i=0; i<len; i++) {
+		crc = crc ^ data[i];
+		for (int j=0; j<8; j++)
+			crc = (crc >> 1) ^ (0xedb88320 & -(crc & 1));
+	}
+	return ~crc;
+}
+
+static uint32_t check_segment(const struct segment *sg)
+{
+    uint32_t sz = sg->end - sg->start;
+
+    if (sg->crc32 != crc32(sg->data, sz))
+	panic();
+
+    return sz;
+}
+
 static void flash_segment(const struct segment *sg)
 {
     uint32_t pagesz = nrfx_nvmc_flash_page_size_get();
+    uint32_t sz = sg->end - sg->start;
+    int retries = 5;
+
+retry:
 
     /* TODO: Haven't got code to handle the UICR yet */
     if (sg->start >= 0x1000000) {
-	progress(sg->end - sg->start);
+	progress(2 * sz);
 	return;
     }
 
@@ -50,6 +79,17 @@ static void flash_segment(const struct segment *sg)
 		             ((uint32_t *) sg->data)[(addr - sg->start) / 4]);
 	progress(4);
     }
+
+    if (0 != memcmp((void *) sg->start, sg->data, sz)) {
+	progress(-(2 * sz));
+	if (retries--)
+	    goto retry;
+
+	// We're in big trouble... the system is probably bricked but we
+	// don't seem to be able to do anything about it. Better to reboot
+	// and hope than to sit here wearing out the flash!
+	panic();
+    }
 }
 
 void flash_all(void)
@@ -61,7 +101,7 @@ void flash_all(void)
     report_progress(0);
 
     for (int i=0; i<lengthof(segments); i++)
-	total_bytes += 2 * (segments[i].end - segments[i].start);
+	total_bytes += 2 * check_segment(segments + i);
 
     for (int i=0; i<lengthof(segments); i++)
         flash_segment(segments + i);

src/main.c

@@ -9,8 +9,23 @@
 #include "board.h"
 #include "flash.h"
 #include "st7789.h"
+#include "util.h"
 #include "wdt.h"
 
+void panic(void)
+{
+#ifdef CONFIG_ST7789
+    st7789_state(-1);
+#endif
+    reboot();
+}
+
+void reboot(void)
+{
+    while (true)
+	    /* stop feeding the dog and we'll automatically reboot */;
+}
+
 void report_progress(int percent)
 {
 #ifdef CONFIG_ST7789
@@ -35,9 +50,7 @@ int main()
 #endif
 
     flash_all();
-
-    while (true)
-	    /* stop feeding the dog and we'll automatically reboot */;
+    reboot();
 
     return 0;
 }

src/st7789.c

@@ -228,6 +228,13 @@ void st7789_state(int percent_complete)
   const uint16_t bg = 0;
   uint16_t color = bg;
 
+  if (percent_complete < 0)
+      fg = 0xf800;
+  else if (percent_complete < 100)
+      fg = 0x033f;
+  else
+      fg = 0xffff;
+
   for (int i=0; i<sizeof(rle); i++) {
     uint8_t rl = rle[i];
     while (rl) {
@@ -247,7 +254,7 @@ void st7789_state(int percent_complete)
 	if (bottomclip) {
 	  memset(linebuffer+2*(240-64), 0, 64*2);
 	}
-	if (y >= (165-percent_complete)) {
+	if (percent_complete >= 1 && y >= (165-percent_complete)) {
 	  fg = 0xffff;
 	}
 

src/util.h

@@ -8,6 +8,8 @@
 
 #define lengthof(x) (sizeof(x) / sizeof((x)[0]))
 
+void panic(void);
+void reboot(void);
 void report_progress(int percent);
 
 #endif /* RELOADER_UTIL_H__ */