On 25/01/2020 16:20, Tom Rini wrote:
Hi Tom,
thanks for having a look!
On Tue, Jan 21, 2020 at 10:23:17AM +0000, Andre Przywara wrote:
From: Maxime Ripard maxime.ripard@bootlin.com
This is needed when importing mainline DTs into U-Boot, as some started using this /omit-if-no-ref/ tag, so won't compile with U-Boot's current dtc copy. This is just a cherry-pick of the patch introducing this feature. Original commit message from Maxime:
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@bootlin.com Reviewed-by: Rob Herring robh@kernel.org Signed-off-by: Andre Przywara andre.przywara@arm.com
scripts/dtc/checks.c | 13 +++++++++++++ scripts/dtc/dtc-lexer.l | 7 +++++++ scripts/dtc/dtc-parser.y | 17 +++++++++++++++++ scripts/dtc/dtc.h | 4 ++++ scripts/dtc/livetree.c | 14 ++++++++++++++ 5 files changed, 55 insertions(+)
diff --git a/scripts/dtc/checks.c b/scripts/dtc/checks.c index c07ba4da9e..40879677c8 100644 --- a/scripts/dtc/checks.c +++ b/scripts/dtc/checks.c @@ -579,6 +579,8 @@ 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);} @@ -609,11 +611,21 @@ 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
*/ @@ -1367,6 +1379,7 @@ 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/scripts/dtc/dtc-lexer.l b/scripts/dtc/dtc-lexer.l index fd825ebba6..615b7ec658 100644 --- a/scripts/dtc/dtc-lexer.l +++ b/scripts/dtc/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/scripts/dtc/dtc-parser.y b/scripts/dtc/dtc-parser.y index 44af170abf..66ff7f7d8e 100644 --- a/scripts/dtc/dtc-parser.y +++ b/scripts/dtc/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);
$$ = $1;}- | devicetree DT_OMIT_NO_REF DT_REF ';'
{struct node *target = get_node_by_ref($1, $3);if (target)omit_node_if_unused(target);elseERROR(&@3, "Label or path %s not found", $3);$$ = $1;@@ -523,6 +536,10 @@ subnode: { $$ = name_node(build_node_delete(), $2); }
- | DT_OMIT_NO_REF subnode
{$$ = omit_node_if_unused($2);}diff --git a/scripts/dtc/dtc.h b/scripts/dtc/dtc.h index 3b18a42b86..6d667701ab 100644 --- a/scripts/dtc/dtc.h +++ b/scripts/dtc/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/scripts/dtc/livetree.c b/scripts/dtc/livetree.c index 57b7db2ed1..81b6c48454 100644 --- a/scripts/dtc/livetree.c +++ b/scripts/dtc/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;
OK, what does this flag _do_ ? I've not been able to make it discard anything in some tests where I scatter it all over dts files.
The idea is to omit *marked* nodes that are *not referenced* by other nodes. This is meant for pinmux nodes and old style clocks. To be useful, it would be *prefixing* those nodes in .dtsi files, so that you can describe all possible pins in the SoC file, for instance, but only those actually used by your board are build into the .dtb. Check https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch... for an example.
Looking at this case for instance I was actually wondering if we should have something that applies to all child nodes. Also I was experimenting with removing nodes that have 'status = "disabled";', but not sure that helps you in your case.
Is there some other flag we also need to pass to dtc to have this be used?
If you build with symbols generation (-@), no nodes are removed, as they might be later used by overlays. Otherwise it's is effect without any extra switch.
Worked for me in this example:
/dts-v1/; / { /omit-if-no-ref/ node1: node1 { compatible = "foo"; value = <17>; };
/omit-if-no-ref/ node2: node2 { compatible = "bar"; value = <37>; };
main { compatible = "baz"; requires = <&node1>; }; };
$ dtc -o test.dtb test.dts && dtc test.dtb
Cheers, Andre.