Add a reset to probe_jedec before we read the chip's IDs

Previous probes might have had too short delays for entering ID mode,
so the chip may still be in the process of entering the ID mode. Due to
that, an additional delay before the reset makes sense.
Add FEATURE_RESET_MASK to deal cleanly with those feature bits.

Maciej Pijanka tested the patch and it fixes probing for him with some
old Atmel chips.

Corresponding to flashrom svn r1216.
Signed-off-by: Sean Nelson <audiohacked@gmail.com>
Signed-off-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@gmx.net>
Acked-by: Anders Juel Jensen <andersjjensen@gmail.com>
Tested-by: Maciej Pijanka <maciej.pijanka@gmail.com>
Acked-by: Sean Nelson <audiohacked@gmail.com> 

flash.h

@@ -83,6 +83,7 @@ enum chipbustype {
 #define FEATURE_LONG_RESET	(0 << 4)
 #define FEATURE_SHORT_RESET	(1 << 4)
 #define FEATURE_EITHER_RESET	FEATURE_LONG_RESET
+#define FEATURE_RESET_MASK	(FEATURE_LONG_RESET | FEATURE_SHORT_RESET)
 #define FEATURE_ADDR_FULL	(0 << 2)
 #define FEATURE_ADDR_MASK	(3 << 2)
 #define FEATURE_ADDR_2AA	(1 << 2)

jedec.c

@@ -142,6 +142,26 @@ static int probe_jedec_common(struct flashchip *flash, unsigned int mask)
 		return 0;
 	}
 
+	/* Earlier probes might have been too fast for the chip to enter ID
+	 * mode completely. Allow the chip to finish this before seeing a
+	 * reset command.
+	 */
+	if (probe_timing_enter)
+		programmer_delay(probe_timing_enter);
+	/* Reset chip to a clean slate */
+	if ((flash->feature_bits & FEATURE_RESET_MASK) == FEATURE_LONG_RESET)
+	{
+		chip_writeb(0xAA, bios + (0x5555 & mask));
+		if (probe_timing_exit)
+			programmer_delay(10);
+		chip_writeb(0x55, bios + (0x2AAA & mask));
+		if (probe_timing_exit)
+			programmer_delay(10);
+	}
+	chip_writeb(0xF0, bios + (0x5555 & mask));
+	if (probe_timing_exit)
+		programmer_delay(probe_timing_exit);
+
 	/* Issue JEDEC Product ID Entry command */
 	chip_writeb(0xAA, bios + (0x5555 & mask));
 	if (probe_timing_enter)
@@ -172,7 +192,7 @@ static int probe_jedec_common(struct flashchip *flash, unsigned int mask)
 	}
 
 	/* Issue JEDEC Product ID Exit command */
-	if ((flash->feature_bits & FEATURE_SHORT_RESET) == FEATURE_LONG_RESET)
+	if ((flash->feature_bits & FEATURE_RESET_MASK) == FEATURE_LONG_RESET)
 	{
 		chip_writeb(0xAA, bios + (0x5555 & mask));
 		if (probe_timing_exit)