Add support for using XIP cache as SRAM (#2932)

* Separate linker scripts out into include files

Allows for much simpler custom linker scripts

* Add customisable heap location, with pico_set_linker_script_var function

* Add kitchen sink test of custom linker scripts

* Separate out rp2_common and platform-specific linker script sections

* More de-duplication

* Make overriding ram locations simpler

* Make it possible to reference default locations in pico_set_linker_script_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 individual files easier

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

* Add simple overlay demo

* Add scripts to bazel build

Use new include_linker_script_dir and use_linker_script_file functions to add the linker arguments

* Move linker scripts out of crt0

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

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

* Rename scripts include directories to standard_scripts and platform_scripts

* Move and add example to Bazel docs for changing linker scripts

* Add cc_library load to new bazel files

* Add excludes.ld files for default memmap

Allows overriding what to exclude from .text/.rodata and put in .data

* Put mem functions in SRAM

These were being placed in Flash due to a missing space, and also are under libc on some compilers

* Rename standard_scripts and platform_scripts to script_include

* Move pico_platform_link stuff into pico_plaftorm

* Remove rigidity from linker include paths

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

* Rename all linker scripts intended to be included to .incl

Required changes to the way bazel views these files

* Separate into section_... files which do only contain one section, and 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

* Add section_extra files to make adding extra sections simpler

* Fix comments, and add some more extra files

* Add generated override files - currently unused, but can be overridden in the future by CMake/bazel functions

* pico_add_linker_script_override_path can now be called after target_link_libraries, as it uses generator expressions

Also add more checks to kitchen_sink

* Add extra post_platform_end sections

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

* review fixups

* Save/restore XIP cache state around flash functions

* Fix PICO_USE_SW_SPIN_LOCKS=0 on RP2350

Use spinlock IDs that are unaffected by E2

* Working XIP SRAM binaries

* Change implementation to use pico_use_xip_sram_for_time_critical instead of new binary types

Adds pico_include_in_generated_section to fill section_generated_... files with lists of include files,
and pico_set_compile_definition to allow setting the same definition multiple times on a target without getting warnings

* Add some CMake function docs

* Fix bazel and RP2350 build

Has missed setting PICO_CRT0_PIN_XIP_SRAM

* Fix bazel build

Ordering of transistions matters

* Improve new __time_critical_func description

Special treatment is no longer in the future

* Add pico_test, and improve SRAM thrashing

* fix bazel build

* fixup merge

* Move memory_xip_ram.incl to match location in other PRs

* Review fixups

Place RAM_SECTION_NAME in .time_critical.text

Typo in __time_critical_func description

* fixup merge

* review fixup

* add memmap_xip_ram.cmake

* some minor cleanup

* Doesn't require data copy for no_flash use_xip_cache_as_ram on RP2040

The code is still loaded before boot on rp2040, so doesn't need copying

* remove copy-paste typo

* Fixes for compatibility with low power

Skip low power unpinning when PICO_USE_XIP_CACHE_AS_RAM is set

Take xip_ram as argument to pico_set_persistent_data_loc, to allow placing normally instead of specifying address

Add pico_critical_xip_sram_test_low_power test to check usin xip_ram for both works

* Improve pico_set_persistent_data_loc description

* add () inside #define

* Update memory_extra.incl examples

PSRAM and xip_ram are now supported by default

* Improve binary type generator expressions

Use PICO_DEFAULT_BINARY_TYPE in the generator expressions, to remove need for PICO_NO_FLASH etc, and fixup the legacy variable handling to that effect

Now throws an error if both PICO_DEFAULT_BINARY_TYPE and one of PICO_NO_FLASH etc are specified - just use PICO_DEFAULT_BINARY_TYPE

* Refactor to place functions using compile definitions instead of linker script injections

This adds section_xip_ram.incl into every linker script, and provides the __in_xip_ram macro to put stuff there

__time_critical_func then uses the PICO_TIME_CRITICAL_PLACEMENT define to select where to place code, so that can be overriden to be __in_xip_ram to place time critical functions in xip_ram

Also works for placing time critical functions in scratch x/y

* pico_use_xip_cache_as_sram -> pico_use_xip_cache_as_ram for consistency

Also re-add note to pico_place_time_critical_functions not to use xip_ram for flash binaries

* fix bazel linting

* remove memory_aliases_xip_ram_only

now identical to memory_aliases_no_flash

* Re-arrange sections.h to be clearer what everything does

All `__in_xxx` macros place directly into linker sections, which are located in the relevant memory

`__scratch_x` and `__scratch_y` are kept as aliases to `__in_scratch_x` and `__in_scratch_y`

`__not_in_flash` is placed using `PICO_NOT_IN_FLASH_PLACEMENT` which defaults to `__in_ram`, and the same for `__time_critical_func`, so they can be placed separately

pico_place_time_critical_functions -> pico_set_time_critical_placement, and add pico_set_not_in_flash_placement

* Make memmap_xip_ram.incl include memmap_no_flash.incl

Removes the ability to override XIP_RAM_ORIGIN and XIP_RAM_LENGTH (to prevent duplicate includes, which Clang doesn't like), but that is fine

* Fixup bazel build

Note that the xip_ram binary type still doesn't work in bazel, as the bazel build doesn't fit in xip_ram

* fix bazel buildifier checks

---------

Co-authored-by: graham sanderson <graham.sanderson@raspberrypi.com>

Author: will-v-pi

bazel/config/BUILD.bazel

@@ -237,6 +237,7 @@ string_flag(
         "no_flash",
         "copy_to_ram",
         "blocked_ram",
+        "xip_ram",
     ],
 )
 

bazel/constraint/BUILD.bazel

@@ -303,3 +303,8 @@ config_setting(
     name = "pico_binary_type_blocked_ram",
     flag_values = {"//bazel/config:PICO_DEFAULT_BINARY_TYPE": "blocked_ram"},
 )
+
+config_setting(
+    name = "pico_binary_type_xip_ram",
+    flag_values = {"//bazel/config:PICO_DEFAULT_BINARY_TYPE": "xip_ram"},
+)

src/common/pico_base_headers/BUILD.bazel

@@ -78,6 +78,10 @@ cc_library(
         "//bazel/constraint:pico_binary_type_no_flash": ["PICO_NO_FLASH=1"],
         "//bazel/constraint:pico_binary_type_copy_to_ram": ["PICO_COPY_TO_RAM=1"],
         "//bazel/constraint:pico_binary_type_blocked_ram": ["PICO_USE_BLOCKED_RAM=1"],
+        "//bazel/constraint:pico_binary_type_xip_ram": [
+            "PICO_XIP_RAM=1",
+            "PICO_NO_FLASH=1",
+        ],
         "//conditions:default": [],
     }),
 )

src/rp2040/pico_platform/memmap_blocked_ram.cmake

@@ -37,6 +37,7 @@ function(pico_add_memmap_link_depends_internal TARGET)
     pico_add_link_depend(${TARGET} ${PICO_SDK_PATH}/src/rp2_common/pico_standard_link/script_include/section_ram_vector_table.incl)
     pico_add_link_depend(${TARGET} ${PICO_SDK_PATH}/src/rp2_common/pico_standard_link/script_include/section_tls.incl)
     pico_add_link_depend(${TARGET} ${PICO_SDK_PATH}/src/rp2_common/pico_standard_link/script_include/section_uninitialized_data.incl)
+    pico_add_link_depend(${TARGET} ${PICO_SDK_PATH}/src/rp2_common/pico_standard_link/script_include/section_xip_ram.incl)
     pico_add_link_depend(${TARGET} ${PICO_SDK_PATH}/src/rp2_common/pico_standard_link/script_include/sections_arm_ex.incl)
     pico_add_link_depend(${TARGET} ${PICO_SDK_PATH}/src/rp2_common/pico_standard_link/script_include/sections_default.incl)
     pico_add_link_depend(${TARGET} ${PICO_SDK_PATH}/src/rp2_common/pico_standard_link/script_include/sections_default_data.incl)

src/rp2040/pico_platform/memmap_blocked_ram.ld

@@ -45,6 +45,7 @@ INCLUDE "memmap_default.incl"
  *         ├── section_extra_post_scratch.incl           rp2_common/pico_standard_link
  *         ├── sections_stack.incl                       rp2_common/pico_standard_link
  *         ├── sections_psram.incl                       rp2040/pico_platform
+ *         ├── section_xip_ram.incl                      rp2_common/pico_standard_link
  *         ├── section_flash_end.incl                    rp2_common/pico_standard_link
  *         ├── section_end.incl                          rp2_common/pico_standard_link
  *         ├── section_generated_post_end.incl           rp2_common/pico_standard_link

src/rp2040/pico_platform/memmap_copy_to_ram.cmake

@@ -36,6 +36,7 @@ function(pico_add_memmap_link_depends_internal TARGET)
     pico_add_link_depend(${TARGET} ${PICO_SDK_PATH}/src/rp2_common/pico_standard_link/script_include/section_ram_vector_table.incl)
     pico_add_link_depend(${TARGET} ${PICO_SDK_PATH}/src/rp2_common/pico_standard_link/script_include/section_tls.incl)
     pico_add_link_depend(${TARGET} ${PICO_SDK_PATH}/src/rp2_common/pico_standard_link/script_include/section_uninitialized_data.incl)
+    pico_add_link_depend(${TARGET} ${PICO_SDK_PATH}/src/rp2_common/pico_standard_link/script_include/section_xip_ram.incl)
     pico_add_link_depend(${TARGET} ${PICO_SDK_PATH}/src/rp2_common/pico_standard_link/script_include/sections_arm_ex.incl)
     pico_add_link_depend(${TARGET} ${PICO_SDK_PATH}/src/rp2_common/pico_standard_link/script_include/sections_copy_to_ram.incl)
     pico_add_link_depend(${TARGET} ${PICO_SDK_PATH}/src/rp2_common/pico_standard_link/script_include/sections_copy_to_ram_data.incl)

src/rp2040/pico_platform/memmap_copy_to_ram.ld

@@ -41,6 +41,7 @@ INCLUDE "memmap_copy_to_ram.incl"
  *         ├── section_extra_post_scratch.incl           rp2_common/pico_standard_link
  *         ├── sections_stack.incl                       rp2_common/pico_standard_link
  *         ├── sections_psram.incl                       rp2040/pico_platform
+ *         ├── section_xip_ram.incl                      rp2_common/pico_standard_link
  *         ├── section_flash_end.incl                    rp2_common/pico_standard_link
  *         ├── section_end.incl                          rp2_common/pico_standard_link
  *         ├── section_generated_post_end.incl           rp2_common/pico_standard_link

src/rp2040/pico_platform/memmap_default.cmake

@@ -37,6 +37,7 @@ function(pico_add_memmap_link_depends_internal TARGET)
     pico_add_link_depend(${TARGET} ${PICO_SDK_PATH}/src/rp2_common/pico_standard_link/script_include/section_ram_vector_table.incl)
     pico_add_link_depend(${TARGET} ${PICO_SDK_PATH}/src/rp2_common/pico_standard_link/script_include/section_tls.incl)
     pico_add_link_depend(${TARGET} ${PICO_SDK_PATH}/src/rp2_common/pico_standard_link/script_include/section_uninitialized_data.incl)
+    pico_add_link_depend(${TARGET} ${PICO_SDK_PATH}/src/rp2_common/pico_standard_link/script_include/section_xip_ram.incl)
     pico_add_link_depend(${TARGET} ${PICO_SDK_PATH}/src/rp2_common/pico_standard_link/script_include/sections_arm_ex.incl)
     pico_add_link_depend(${TARGET} ${PICO_SDK_PATH}/src/rp2_common/pico_standard_link/script_include/sections_default.incl)
     pico_add_link_depend(${TARGET} ${PICO_SDK_PATH}/src/rp2_common/pico_standard_link/script_include/sections_default_data.incl)

src/rp2040/pico_platform/memmap_default.ld

@@ -42,6 +42,7 @@ INCLUDE "memmap_default.incl"
  *         ├── section_extra_post_scratch.incl           rp2_common/pico_standard_link
  *         ├── sections_stack.incl                       rp2_common/pico_standard_link
  *         ├── sections_psram.incl                       rp2040/pico_platform
+ *         ├── section_xip_ram.incl                      rp2_common/pico_standard_link
  *         ├── section_flash_end.incl                    rp2_common/pico_standard_link
  *         ├── section_end.incl                          rp2_common/pico_standard_link
  *         ├── section_generated_post_end.incl           rp2_common/pico_standard_link

src/rp2040/pico_platform/memmap_no_flash.cmake

@@ -29,6 +29,7 @@ function(pico_add_memmap_link_depends_internal TARGET)
     pico_add_link_depend(${TARGET} ${PICO_SDK_PATH}/src/rp2_common/pico_standard_link/script_include/section_persistent_data.incl)
     pico_add_link_depend(${TARGET} ${PICO_SDK_PATH}/src/rp2_common/pico_standard_link/script_include/section_tls.incl)
     pico_add_link_depend(${TARGET} ${PICO_SDK_PATH}/src/rp2_common/pico_standard_link/script_include/section_uninitialized_data.incl)
+    pico_add_link_depend(${TARGET} ${PICO_SDK_PATH}/src/rp2_common/pico_standard_link/script_include/section_xip_ram.incl)
     pico_add_link_depend(${TARGET} ${PICO_SDK_PATH}/src/rp2_common/pico_standard_link/script_include/sections_arm_ex.incl)
     pico_add_link_depend(${TARGET} ${PICO_SDK_PATH}/src/rp2_common/pico_standard_link/script_include/sections_no_flash.incl)
     pico_add_link_depend(${TARGET} ${PICO_SDK_PATH}/src/rp2_common/pico_standard_link/script_include/sections_no_flash_data.incl)