target: MMU-aware init for memory read/write

Start switching MMU handling over to a more sensible scheme.
Having an mmu() method enables MMU-aware behaviors.  Not having
one kicks in simpler ones, with no distinction between virtual
and physical addresses.

Currently only a handful of targets have methods to read/write
physical memory:  just arm720, arm920, and arm926.  They should
all initialize OK now, but the arm*20 parts don't do the "extra"
stuff arm926 does (which should arguably be target-generic).

Also simplify how target_init() loops over all targets by making
it be a normal "for" loop, instead of scattering its three parts
to the four winds.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>

doc/openocd.texi

@@ -5051,9 +5051,11 @@ about what TAP is the current target, or about MMU configuration.
 Display contents of address @var{addr}, as
 32-bit words (@command{mdw}), 16-bit halfwords (@command{mdh}),
 or 8-bit bytes (@command{mdb}).
+When the current target has an MMU which is present and active,
+@var{addr} is interpreted as a virtual address.
+Otherwise, or if the optional @var{phys} flag is specified,
+@var{addr} is interpreted as a physical address.
 If @var{count} is specified, displays that many units.
-@var{phys} is an optional flag to indicate to use
-physical address and bypass MMU
 (If you want to manipulate the data instead of displaying it,
 see the @code{mem2array} primitives.)
 @end deffn
@@ -5062,10 +5064,12 @@ see the @code{mem2array} primitives.)
 @deffnx Command mwh [phys] addr halfword
 @deffnx Command mwb [phys] addr byte
 Writes the specified @var{word} (32 bits),
-@var{halfword} (16 bits), or @var{byte} (8-bit) pattern,
+@var{halfword} (16 bits), or @var{byte} (8-bit) value,
 at the specified address @var{addr}.
-@var{phys} is an optional flag to indicate to use
-physical address and bypass MMU
+When the current target has an MMU which is present and active,
+@var{addr} is interpreted as a virtual address.
+Otherwise, or if the optional @var{phys} flag is specified,
+@var{addr} is interpreted as a physical address.
 @end deffn
 
 

src/target/target.c

@@ -756,11 +756,12 @@ err_write_phys_memory(struct target_s *target, uint32_t address,
 
 int target_init(struct command_context_s *cmd_ctx)
 {
-	target_t *target = all_targets;
+	struct target_s *target;
 	int retval;
 
-	while (target)
-	{
+	for (target = all_targets; target; target = target->next) {
+		struct target_type_s *type = target->type;
+
 		target_reset_examined(target);
 		if (target->type->examine == NULL)
 		{
@@ -773,22 +774,6 @@ int target_init(struct command_context_s *cmd_ctx)
 			return retval;
 		}
 
-		/* Set up default functions if none are provided by target */
-		if (target->type->virt2phys == NULL)
-		{
-			target->type->virt2phys = identity_virt2phys;
-		}
-
-		if (target->type->read_phys_memory == NULL)
-		{
-			target->type->read_phys_memory = err_read_phys_memory;
-		}
-
-		if (target->type->write_phys_memory == NULL)
-		{
-			target->type->write_phys_memory = err_write_phys_memory;
-		}
-
 		/**
 		 * @todo MCR/MRC are ARM-specific; don't require them in
 		 * all targets, or for ARMs without coprocessors.
@@ -833,11 +818,45 @@ int target_init(struct command_context_s *cmd_ctx)
 		target->type->run_algorithm_imp = target->type->run_algorithm;
 		target->type->run_algorithm = target_run_algorithm_imp;
 
-		if (target->type->mmu == NULL)
-		{
-			target->type->mmu = no_mmu;
+		/* Sanity-check MMU support ... stub in what we must, to help
+		 * implement it in stages, but warn if we need to do so.
+		 */
+		if (type->mmu) {
+			if (type->write_phys_memory == NULL) {
+				LOG_ERROR("type '%s' is missing %s",
+						type->name,
+						"write_phys_memory");
+				type->write_phys_memory = err_write_phys_memory;
+			}
+			if (type->read_phys_memory == NULL) {
+				LOG_ERROR("type '%s' is missing %s",
+						type->name,
+						"read_phys_memory");
+				type->read_phys_memory = err_read_phys_memory;
+			}
+			if (type->virt2phys == NULL) {
+				LOG_ERROR("type '%s' is missing %s",
+						type->name,
+						"virt2phys");
+				type->virt2phys = identity_virt2phys;
+			}
+
+		/* Make sure no-MMU targets all behave the same:  make no
+		 * distinction between physical and virtual addresses, and
+		 * ensure that virt2phys() is always an identity mapping.
+		 */
+		} else {
+			if (type->write_phys_memory
+					|| type->read_phys_memory
+					|| type->virt2phys)
+				LOG_WARNING("type '%s' has broken MMU hooks",
+						type->name);
+
+			type->mmu = no_mmu;
+			type->write_phys_memory = type->write_memory;
+			type->read_phys_memory = type->read_memory;
+			type->virt2phys = identity_virt2phys;
 		}
-		target = target->next;
 	}
 
 	if (all_targets)