target armv7m: multi-block erase check

Tested on PSoC6 (Cortex-M0+ core), onboard KitProg2 in CMSIS-DAP mode,
adapter_khz=1000.
Plain read:
	flash read_bank 0 /dev/null
takes 48 seconds.

erase_check without this change:
	flash erase_check 0
takes horrible 149 seconds!!

And the same command with the change applied takes 1.8 seconds.
Quite a difference.

Remove the erase-value=0 version of algorithm as the new one can check
for any value.

If the target is an insane slow clocked CPU (under 1MHz) algo
timeouts. Blocks checked so far are returned and the next call
uses increased timeout.

Change-Id: Ic0899011256d2114112e67c0b51fab4f6230d9cd
Signed-off-by: Tomas Vanek <vanekt@fbl.cz>
Reviewed-on: http://openocd.zylin.com/4298
Tested-by: jenkins
Reviewed-by: Jonas Norling <jonas.norling@cyanconnode.com>
Reviewed-by: Andreas Bolsch <hyphen0break@gmail.com>

contrib/loaders/erase_check/Makefile

@@ -12,7 +12,7 @@ STM8_OBJCOPY ?= $(STM8_CROSS_COMPILE)objcopy
 
 STM8_AFLAGS =
 
-arm: armv4_5_erase_check.inc armv7m_erase_check.inc armv7m_0_erase_check.inc
+arm: armv4_5_erase_check.inc armv7m_erase_check.inc
 
 armv4_5_%.elf: armv4_5_%.s
 	$(ARM_AS) $(ARM_AFLAGS) $< -o $@

contrib/loaders/erase_check/armv7m_0_erase_check.inc

@@ -1,2 +0,0 @@
-/* Autogenerated with ../../../src/helper/bin2char.sh */
-0x03,0x78,0x01,0x30,0x1a,0x43,0x01,0x39,0xfa,0xd1,0x00,0xbe,

contrib/loaders/erase_check/armv7m_0_erase_check.s

@@ -1,45 +0,0 @@
-/***************************************************************************
- *   Copyright (C) 2014 by Jeff Ciesielski                                 *
- *   jeffciesielski@gmail.com                                              *
- *                                                                         *
- *   Based on the armv7m erase checker by:                                 *
- *   Copyright (C) 2010 by Spencer Oliver                                  *
- *   spen@spen-soft.co.uk                                                  *
- *                                                                         *
- *   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 program is distributed in the hope that it will be useful,       *
- *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
- *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
- *   GNU General Public License for more details.                          *
- *                                                                         *
- ***************************************************************************/
-
-/*
-	parameters:
-	r0 - address in
-	r1 - byte count
-	r2 - mask - result out
-*/
-
-	.text
-	.syntax unified
-	.cpu cortex-m0
-	.thumb
-	.thumb_func
-
-	.align	2
-
-loop:
-	ldrb	r3, [r0]
-	adds	r0, #1
-	orrs	r2, r2, r3
-	subs	r1, r1, #1
-	bne		loop
-end:
-	bkpt	#0
-
-	.end

contrib/loaders/erase_check/armv7m_erase_check.inc

@@ -1,2 +1,4 @@
 /* Autogenerated with ../../../src/helper/bin2char.sh */
-0x03,0x78,0x01,0x30,0x1a,0x40,0x01,0x39,0xfa,0xd1,0x00,0xbe,
+0x02,0x68,0x12,0x42,0x0d,0xd0,0x43,0x68,0x1c,0x68,0x04,0x33,0x8c,0x42,0x05,0xd1,
+0x01,0x3a,0xf9,0xd1,0x01,0x24,0x04,0x60,0x08,0x30,0xf1,0xe7,0x00,0x24,0xfa,0xe7,
+0x00,0x00,0x00,0xbe,

contrib/loaders/erase_check/armv7m_erase_check.s

@@ -20,9 +20,8 @@
 
 /*
 	parameters:
-	r0 - address in
-	r1 - byte count
-	r2 - mask - result out
+	r0 - pointer to struct { uint32_t size_in_result_out, uint32_t addr }
+	r1 - value to check
 */
 
 	.text
@@ -33,13 +32,42 @@
 
 	.align	2
 
-loop:
-	ldrb	r3, [r0]
-	adds	r0, #1
-	ands	r2, r2, r3
-	subs	r1, r1, #1
-	bne		loop
-end:
+BLOCK_SIZE_RESULT	= 0
+BLOCK_ADDRESS		= 4
+SIZEOF_STRUCT_BLOCK	= 8
+
+start:
+block_loop:
+	ldr	r2, [r0, #BLOCK_SIZE_RESULT]	/* get size */
+	tst	r2, r2
+	beq	done
+
+	ldr	r3, [r0, #BLOCK_ADDRESS]	/* get address */
+
+word_loop:
+	ldr	r4, [r3]	/* read word */
+	adds	r3, #4
+
+	cmp	r4, r1
+	bne	not_erased
+
+	subs	r2, #1
+	bne	word_loop
+
+	movs	r4, #1		/* block is erased */
+save_result:
+	str	r4, [r0, #BLOCK_SIZE_RESULT]
+	adds	r0, #SIZEOF_STRUCT_BLOCK
+	b	block_loop
+
+not_erased:
+	movs	r4, #0
+	b	save_result
+
+/* Avoid padding at .text segment end. Otherwise exit point check fails. */
+        .skip   ( . - start + 2) & 2, 0
+
+done:
 	bkpt	#0
 
 	.end