Add pico_low_power library by will-v-pi · Pull Request #2852 · raspberrypi/pico-sdk

will-v-pi · 2026-03-06T18:05:49Z

This adds a pico_low_power library, which allows going to sleep, dormant, and powman pstates.

Also adds bitsets and hardware_rosc, to support the low power stuff.

Includes a possible fix for #2420 to get the bazel rp2040 clang build working

Requires the include linker scripts in #2841, so will need rebasing once those are merged

Also requires raspberrypi/picotool#298 when putting persistent data in XIP SRAM

See low_power.h for documentation

Allows for much simpler custom linker scripts

…ript_var variables Means that CMake doesn't need to know the default memory addresses for different platforms

…l files easier Restructured so that it includes the platform-specific files before common ones, so common ones can be overridden

Use new include_linker_script_dir and use_linker_script_file functions to add the linker arguments

Breaking change for Bazel builds using different binary types, instead of setting PICO_DEFAULT_LINKER_SCRIPT to eg `//src/rp2_common/pico_crt0:no_flash_linker_script` it is now `//src/rp2_common/pico_standard_link:no_flash_linker_script`

Treat rp2040 layout (boot2 instead of embedded blocks) as the outlier

…cripts

lurch · 2026-03-06T18:12:40Z

src/common/pico_util/include/pico/util/bitset.h

+
+static inline generic_bitset_t *bitset_write_word(generic_bitset_t *bitset, uint word_num, uint32_t value) {
+    check_bitset(bitset);
+    if (word_num < bitset_word_size(bitset)) {


Should this raise an error if word_num >= bitset_word_size(bitset) ?

This is a question for @kilograham, but given that the other functions don't throw any errors when you attempt to pass a value that is outside the range and just return 0/do nothing, I think this one should also not throw an error?

src/common/pico_util/include/pico/util/bitset.h

src/rp2_common/hardware_clocks/include/hardware/clocks.h

src/rp2_common/hardware_irq/include/hardware/irq.h

src/rp2_common/hardware_irq/irq.c

src/rp2_common/hardware_powman/include/hardware/powman.h

src/rp2_common/hardware_rosc/include/hardware/rosc.h

lurch · 2026-03-06T19:25:58Z

src/rp2_common/hardware_rosc/rosc.c

+uint rosc_find_freq_mhz(uint32_t low_mhz, uint32_t high_mhz) {
+    // TODO: This could be a lot better
+    rosc_set_div(1);
+    for (uint32_t code = 0; code <= 0x77777777u; code = next_rosc_code(code)) {


My goodness that's a large search space 😂

src/rp2_common/hardware_rosc/rosc.c

… function names (eg clock_dest_set_all)

Co-authored-by: Andrew Scheller <lurch@durge.org>

Add PICO_LINKER_SCRIPT_INCLUDE_DIRS and PICO_LINKER_DEFAULT_LOCATIONS_PATH, instead of hardcoded paths under PICO_LINKER_SCRIPT_PATH Also improve pico_set_linker_script_var and pico_add_linker_script_override_path to better utilise generator expressions

Required changes to the way bazel views these files

…d sections_... which contain multiple Only exceptions are section_..._data and section_bss, as these contain data/bss and tdata/tbss - these are kept together as they are treated as a single section

lurch · 2026-03-19T14:03:05Z

src/common/pico_util/include/pico/util/bitset.h

+typedef uint32_t tiny_encoded_bitset_t;
+typedef uint64_t encoded_bitset_t;
+
+#define encoded_bitset_empty() 0
+#define encoded_bitset_of1(v) (1u | ((v) << 8))
+#define encoded_bitset_of2(v1, v2) (2u | ((v1) << 8) | ((v2) << 16))
+#define encoded_bitset_of3(v1, v2, v3) (3u | ((v1) << 8) | ((v2) << 16) | (((v3) << 24)))
+#define encoded_bitset_of4(v1, v2, v3, v4) (4u | ((v1) << 8) | ((v2) << 16) | (((v3) << 24)) | (((uint64_t)(v4)) << 32))
+#define encoded_bitset_of5(v1, v2, v3, v4, v5) (5u | ((v1) << 8) | ((v2) << 16) | (((v3) << 24)) | (((uint64_t)((v4) | ((v5)<<8u))) << 32))
+
+#define encoded_bitset_foreach(bitset, x) ({ \
+    for(uint _i=0;_i<((bitset)&0xffu);_i++) {  \
+        uint bit = (uint8_t)((bitset) >> (8 * _i)); \
+        x;                                   \
+    }                                        \
+})


AFAICT it looks like this encoded_bitset stuff is only used in kitchen_sink.c, so maybe it's not actually needed? 🤷

That’ll be a question for @kilograham

…n in the future by CMake/bazel functions

…ink_libraries, as it uses generator expressions Also add more checks to kitchen_sink

Intended for platform specific overrides, whereas post_end is for cross-platform overrides, similar to section_end vs section_platform_end

Existing method of just setting the linker script didn't work, because the PICO_NO_FLASH/PICO_COPY_TO_RAM define was only available in pico_platform, but needed to be propogated to things that only use pico_base_headers

…e for individual binaries Can remove full no_flash etc test builds, as there can now be kitchen_sink_no_flash etc builds like in CMake

Now uses single linker_scripts function to allow both including and linking scripts Returns DefaultInfo with all necessary files Prepends ctx.label.workspace_root to link_include_dir Gets link_include_dir directly from the include_scripts passed in

… bazel Also adds pico_set_linker_script transition to set linker script for individual binaries

Remove whitespace, and rename memory_aliases_default to memory_aliases_flash, as it applies to copy_to_ram too

Commits on this branch are very messy due to being on top of changing linker scripts, so definitely need squashing before final merge

bazel/util/transition.bzl

will-v-pi added 15 commits March 6, 2026 15:29

Separate linker scripts out into include files

b8f699f

Allows for much simpler custom linker scripts

Add customisable heap location, with pico_set_linker_script_var function

6dc06e6

Add kitchen sink test of custom linker scripts

727cabd

Separate out rp2_common and platform-specific linker script sections

3a83dc7

More de-duplication

4b1a3ec

Make overriding ram locations simpler

ae97a22

Make it possible to reference default locations in pico_set_linker_sc…

3811e67

…ript_var variables Means that CMake doesn't need to know the default memory addresses for different platforms

Add pico_add_linker_script_override_path to make overriding individua…

a20f86a

…l files easier Restructured so that it includes the platform-specific files before common ones, so common ones can be overridden

Add simple overlay demo

6bd9e5b

Add scripts to bazel build

2bf8555

Use new include_linker_script_dir and use_linker_script_file functions to add the linker arguments

Move linker scripts out of crt0

fe2d56b

Breaking change for Bazel builds using different binary types, instead of setting PICO_DEFAULT_LINKER_SCRIPT to eg `//src/rp2_common/pico_crt0:no_flash_linker_script` it is now `//src/rp2_common/pico_standard_link:no_flash_linker_script`

Make rp2350 text sections the default

1bd7089

Treat rp2040 layout (boot2 instead of embedded blocks) as the outlier

Rename scripts include directories to standard_scripts and platform_s…

72adb67

…cripts

Move and add example to Bazel docs for changing linker scripts

e47fe09

Add cc_library load to new bazel files

9c0ed0c