A number of platforms have a need to reduce the number of DT nodes,
mostly because of two similar constraints: the size of the DT blob, and
the time it takes to parse it.
As the DT is used in more and more SoCs, and by more projects, some
constraints start to appear in bootloaders running from SRAM with an
order of magnitude of 10kB. A typical DT is in the same order of
magnitude, so any effort to reduce the blob size is welcome in such an
environment.
Some platforms also want to reach very fast boot time, and the time it
takes to parse a typical DT starts to be noticeable.
Both of these issues can be mitigated by reducing the number of nodes in
the DT. The biggest provider of nodes is usually the pin controller and
its subnodes, usually one for each valid pin configuration in a given
SoC.
Obviously, a single, fixed, set of these nodes will be used by a given
board, so we can introduce a node property that will tell the DT
compiler to drop the nodes when they are not referenced in the tree, and
as such wouldn't be useful in the targetted system.
Signed-off-by: Maxime Ripard <maxime.ripard@xxxxxxxxxxx>
---
Changes from v1:
- Rename the property from delete-if-unreferenced to omit-if-no-ref
- Change the various variables in the code to reflect this
- Added support to set the property on a label instead of a full node
- Also take into account the reference by path, and not only by
phandle
- Prune the unused nodes in a fixup pass, and not during the tree
flattening that allows to have the same behaviour when having an
output to a format other than dtb or asm
- Rebased on current master
---
checks.c | 13 +++++++++++++
dtc-lexer.l | 7 +++++++
dtc-parser.y | 17 +++++++++++++++++
dtc.h | 4 ++++
livetree.c | 14 ++++++++++++++
5 files changed, 55 insertions(+)
diff --git a/checks.c b/checks.c
index dca45aca73d7..a2cc1036c915 100644
--- a/checks.c
+++ b/checks.c
@@ -584,6 +584,8 @@ static void fixup_phandle_references(struct check *c, struct dt_info *dti,
phandle = get_node_phandle(dt, refnode);
*((fdt32_t *)(prop->val.val + m->offset)) = cpu_to_fdt32(phandle);
+
+ reference_node(refnode);
}
}
}
@@ -614,11 +616,21 @@ static void fixup_path_references(struct check *c, struct dt_info *dti,
path = refnode->fullpath;
prop->val = data_insert_at_marker(prop->val, m, path,
strlen(path) + 1);
+
+ reference_node(refnode);
}
}
}
ERROR(path_references, fixup_path_references, NULL, &duplicate_node_names);
+static void fixup_omit_unused_nodes(struct check *c, struct dt_info *dti,
+ struct node *node)
+{
+ if (node->omit_if_unused && !node->is_referenced)
+ delete_node(node);
+}
+ERROR(omit_unused_nodes, fixup_omit_unused_nodes, NULL, &phandle_references, &path_references);
+
/*
* Semantic checks
*/
@@ -1547,6 +1559,7 @@ static struct check *check_table[] = {
&explicit_phandles,
&phandle_references, &path_references,
+ &omit_unused_nodes,
&address_cells_is_cell, &size_cells_is_cell, &interrupt_cells_is_cell,
&device_type_is_string, &model_is_string, &status_is_string,
diff --git a/dtc-lexer.l b/dtc-lexer.l
index fd825ebba69c..615b7ec6588f 100644
--- a/dtc-lexer.l
+++ b/dtc-lexer.l
@@ -153,6 +153,13 @@ static void PRINTF(1, 2) lexical_error(const char *fmt, ...);
return DT_DEL_NODE;
}
+<*>"/omit-if-no-ref/" {
+ DPRINT("Keyword: /omit-if-no-ref/\n");
+ DPRINT("<PROPNODENAME>\n");
+ BEGIN(PROPNODENAME);
+ return DT_OMIT_NO_REF;
+ }
+
<*>{LABEL}: {
DPRINT("Label: %s\n", yytext);
yylval.labelref = xstrdup(yytext);
diff --git a/dtc-parser.y b/dtc-parser.y
index 25e92d64305c..011a5b25539a 100644
--- a/dtc-parser.y
+++ b/dtc-parser.y
@@ -63,6 +63,7 @@ extern bool treesource_error;
%token DT_BITS
%token DT_DEL_PROP
%token DT_DEL_NODE
+%token DT_OMIT_NO_REF
%token <propnodename> DT_PROPNODENAME
%token <integer> DT_LITERAL
%token <integer> DT_CHAR_LITERAL
@@ -217,6 +218,18 @@ devicetree:
ERROR(&@3, "Label or path %s not found", $3);
+ $$ = $1;
+ }
+ | devicetree DT_OMIT_NO_REF DT_REF ';'
+ {
+ struct node *target = get_node_by_ref($1, $3);
+
+ if (target)
+ omit_node_if_unused(target);
+ else
+ ERROR(&@3, "Label or path %s not found", $3);
+
+
$$ = $1;
}
;
@@ -523,6 +536,10 @@ subnode:
{
$$ = name_node(build_node_delete(), $2);
}
+ | DT_OMIT_NO_REF subnode
+ {
+ $$ = omit_node_if_unused($2);
+ }
| DT_LABEL subnode
{
add_label(&$2->labels, $1);
diff --git a/dtc.h b/dtc.h
index 3b18a42b866e..6d667701ab6a 100644
--- a/dtc.h
+++ b/dtc.h
@@ -168,6 +168,8 @@ struct node {
struct label *labels;
const struct bus_type *bus;
+
+ bool omit_if_unused, is_referenced;
};
#define for_each_label_withdel(l0, l) \
@@ -202,6 +204,8 @@ struct property *reverse_properties(struct property *first);
struct node *build_node(struct property *proplist, struct node *children);
struct node *build_node_delete(void);
struct node *name_node(struct node *node, char *name);
+struct node *omit_node_if_unused(struct node *node);
+struct node *reference_node(struct node *node);
struct node *chain_node(struct node *first, struct node *list);
struct node *merge_nodes(struct node *old_node, struct node *new_node);
struct node *add_orphan_node(struct node *old_node, struct node *new_node, char *ref);
diff --git a/livetree.c b/livetree.c
index f691c9b5c935..6e4c367f54b3 100644
--- a/livetree.c
+++ b/livetree.c
@@ -134,6 +134,20 @@ struct node *name_node(struct node *node, char *name)
return node;
}
+struct node *omit_node_if_unused(struct node *node)
+{
+ node->omit_if_unused = 1;
+
+ return node;
+}
+
+struct node *reference_node(struct node *node)
+{
+ node->is_referenced = 1;
+
+ return node;
+}
+
struct node *merge_nodes(struct node *old_node, struct node *new_node)
{
struct property *new_prop, *old_prop;
--
2.17.0
--
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