Merge patch series "Tidy up use of 'SPL' and CONFIG_SPL_BUILD"WIP/11Oct2024

Simon Glass <sjg@chromium.org> says:

When the SPL build-phase was first created it was designed to solve a
particular problem (the need to init SDRAM so that U-Boot proper could
be loaded). It has since expanded to become an important part of U-Boot,
with three phases now present: TPL, VPL and SPL

Due to this history, the term 'SPL' is used to mean both a particular
phase (the one before U-Boot proper) and all the non-proper phases.
This has become confusing.

For a similar reason CONFIG_SPL_BUILD is set to 'y' for all 'SPL'
phases, not just SPL. So code which can only be compiled for actual SPL,
for example, must use something like this:

   #if defined(CONFIG_SPL_BUILD) && !defined(CONFIG_TPL_BUILD)

In Makefiles we have similar issues. SPL_ has been used as a variable
which expands to either SPL_ or nothing, to chose between options like
CONFIG_BLK and CONFIG_SPL_BLK. When TPL appeared, a new SPL_TPL variable
was created which expanded to 'SPL_', 'TPL_' or nothing. Later it was
updated to support 'VPL_' as well.

This series starts a change in terminology and usage to resolve the
above issues:

- The word 'xPL' is used instead of 'SPL' to mean a non-proper build
- A new CONFIG_XPL_BUILD define indicates that the current build is an
  'xPL' build
- The existing CONFIG_SPL_BUILD is changed to mean SPL; it is not now
  defined for TPL and VPL phases
- The existing SPL_ Makefile variable is renamed to SPL_
- The existing SPL_TPL Makefile variable is renamed to PHASE_

It should be noted that xpl_phase() can generally be used instead of
the above CONFIGs without a code-space or run-time penalty.

This series does not attempt to convert all of U-Boot to use this new
terminology but it makes a start. In particular, renaming spl.h and
common/spl seems like a bridge too far at this point.

The series is fully bisectable. It has also been checked to ensure there
are no code-size changes on any commit.

9 files changed, 147 insertions, 48 deletions

diff --git a/doc/develop/distro.rst b/doc/develop/distro.rst
index 9e715b23ebb..637bc27fc2d 100644
--- a/doc/develop/distro.rst
+++ b/doc/develop/distro.rst
@@ -189,7 +189,7 @@ TO BE UPDATED:
 
 In your board configuration file, include the following::
 
-    #ifndef CONFIG_SPL_BUILD
+    #ifndef CONFIG_XPL_BUILD
     #include <config_distro_bootcmd.h>
     #endif
 
@@ -316,7 +316,7 @@ that it supports the correct set of possible boot device types. To provide this
 configuration, simply define macro BOOT_TARGET_DEVICES prior to including
 <config_distro_bootcmd.h>. For example::
 
-    #ifndef CONFIG_SPL_BUILD
+    #ifndef CONFIG_XPL_BUILD
     #define BOOT_TARGET_DEVICES(func) \
             func(MMC, mmc, 1) \
             func(MMC, mmc, 0) \
diff --git a/doc/develop/index.rst b/doc/develop/index.rst
index cbea38d4323..c23192c2770 100644
--- a/doc/develop/index.rst
+++ b/doc/develop/index.rst
@@ -39,6 +39,7 @@ Implementation
    distro
    driver-model/index
    environment
+   init
    expo
    cedit
    event
diff --git a/doc/develop/init.rst b/doc/develop/init.rst
new file mode 100644
index 00000000000..ce985781bb4
--- /dev/null
+++ b/doc/develop/init.rst
@@ -0,0 +1,93 @@
+.. SPDX-License-Identifier: GPL-2.0+
+
+Board Initialisation Flow
+-------------------------
+
+This is the intended start-up flow for boards. This should apply for both
+xPL and U-Boot proper (i.e. they both follow the same rules).
+
+Note: "xPL" stands for "any Program Loader", including SPL (Secondary
+Program Loader), TPL (Tertiary Program Loader) and VPL (Verifying Program
+Loader). The boot sequence is TPL->VPL->SPL->U-Boot proper
+
+At present, xPL mostly uses a separate code path, but the function names
+and roles of each function are the same. Some boards or architectures
+may not conform to this.  At least most ARM boards which use
+CONFIG_xPL_FRAMEWORK conform to this.
+
+Execution typically starts with an architecture-specific (and possibly
+CPU-specific) start.S file, such as:
+
+- arch/arm/cpu/armv7/start.S
+- arch/powerpc/cpu/mpc83xx/start.S
+- arch/mips/cpu/start.S
+
+and so on. From there, three functions are called; the purpose and
+limitations of each of these functions are described below.
+
+lowlevel_init()
+~~~~~~~~~~~~~~~
+
+- purpose: essential init to permit execution to reach board_init_f()
+- no global_data or BSS
+- there is no stack (ARMv7 may have one but it will soon be removed)
+- must not set up SDRAM or use console
+- must only do the bare minimum to allow execution to continue to
+  board_init_f()
+- this is almost never needed
+- return normally from this function
+
+board_init_f()
+~~~~~~~~~~~~~~
+
+- purpose: set up the machine ready for running board_init_r():
+  i.e. SDRAM and serial UART
+- global_data is available
+- stack is in SRAM
+- BSS is not available, so you cannot use global/static variables,
+  only stack variables and global_data
+
+Non-xPL-specific notes:
+
+    - dram_init() is called to set up DRAM. If already done in xPL this
+      can do nothing
+
+xPL-specific notes:
+
+    - you can override the entire board_init_f() function with your own
+      version as needed.
+    - preloader_console_init() can be called here in extremis
+    - should set up SDRAM, and anything needed to make the UART work
+    - there is no need to clear BSS, it will be done by crt0.S
+    - for specific scenarios on certain architectures an early BSS *can*
+      be made available (via CONFIG_SPL_EARLY_BSS by moving the clearing
+      of BSS prior to entering board_init_f()) but doing so is discouraged.
+      Instead it is strongly recommended to architect any code changes
+      or additions such to not depend on the availability of BSS during
+      board_init_f() as indicated in other sections of this README to
+      maintain compatibility and consistency across the entire code base.
+    - must return normally from this function (don't call board_init_r()
+      directly)
+
+Here the BSS is cleared. For xPL, if CONFIG_xPL_STACK_R is defined, then at
+this point the stack and global_data are relocated to below
+CONFIG_xPL_STACK_R_ADDR. For non-xPL, U-Boot is relocated to run at the top of
+memory.
+
+board_init_r()
+~~~~~~~~~~~~~~
+
+    - purpose: main execution, common code
+    - global_data is available
+    - SDRAM is available
+    - BSS is available, all static/global variables can be used
+    - execution eventually continues to main_loop()
+
+Non-xPL-specific notes:
+
+    - U-Boot is relocated to the top of memory and is now running from
+      there.
+
+xPL-specific notes:
+
+    - stack is optionally in SDRAM, if CONFIG_xPL_STACK_R is defined
diff --git a/doc/develop/logging.rst b/doc/develop/logging.rst
index 704a6bf1d84..d7a40c94bf0 100644
--- a/doc/develop/logging.rst
+++ b/doc/develop/logging.rst
@@ -292,7 +292,7 @@ Convert debug() statements in the code to log() statements
 
 Convert error() statements in the code to log() statements
 
-Figure out what to do with BUG(), BUG_ON() and warn_non_spl()
+Figure out what to do with BUG(), BUG_ON() and warn_non_xpl()
 
 Add a way to browse log records
 
diff --git a/doc/develop/qconfig.rst b/doc/develop/qconfig.rst
index 123779eab17..a18f32470ca 100644
--- a/doc/develop/qconfig.rst
+++ b/doc/develop/qconfig.rst
@@ -226,7 +226,7 @@ Available options
    Look for moved config options in spl/include/autoconf.mk instead of
    include/autoconf.mk.  This is useful for moving options for SPL build
    because SPL related options (mostly prefixed with CONFIG_SPL\_) are
-   sometimes blocked by CONFIG_SPL_BUILD ifdef conditionals.
+   sometimes blocked by CONFIG_XPL_BUILD ifdef conditionals.
 
  -j, --jobs
    Specify the number of threads to run simultaneously.  If not specified,
diff --git a/doc/develop/spl.rst b/doc/develop/spl.rst
index 4bb48e6b7b3..aa6d28fa333 100644
--- a/doc/develop/spl.rst
+++ b/doc/develop/spl.rst
@@ -1,11 +1,12 @@
-Generic SPL framework
+Generic xPL framework
 =====================
 
 Overview
 --------
 
-To unify all existing implementations for a secondary program loader (SPL)
-and to allow simply adding of new implementations this generic SPL framework
+To unify all existing implementations for secondary/tertiary program loaders
+(generically called xPL)
+and to allow simply adding of new implementations this generic xPL framework
 has been created. With this framework almost all source files for a board
 can be reused. No code duplication or symlinking is necessary anymore.
 
@@ -13,36 +14,39 @@ can be reused. No code duplication or symlinking is necessary anymore.
 How it works
 ------------
 
-The object files for SPL are built separately and placed in the "spl" directory.
-The final binaries which are generated are u-boot-spl, u-boot-spl.bin and
-u-boot-spl.map.
+The object files for xPL are built separately and placed in a subdirectory
+("spl", "tpl" or "vpl").
+The final binaries which are generated for SPL are u-boot-spl, u-boot-spl.bin
+and u-boot-spl.map
 
-A config option named CONFIG_SPL_BUILD is enabled by Kconfig for SPL.
-Source files can therefore be compiled for SPL with different settings.
+A config option named CONFIG_XPL_BUILD is enabled by Kconfig for xPL builds.
+Source files can therefore be compiled for xPL with different settings.
 
 For example::
 
-   ifeq ($(CONFIG_SPL_BUILD),y)
+   ifeq ($(CONFIG_XPL_BUILD),y)
    obj-y += board_spl.o
    else
    obj-y += board.o
    endif
 
-   obj-$(CONFIG_SPL_BUILD) += foo.o
+   obj-$(CONFIG_XPL_BUILD) += foo.o
 
-   #ifdef CONFIG_SPL_BUILD
+   if (IS_ENABLED(CONFIG_XPL_BUILD))
            foo();
-   #endif
 
+   if (xpl_phase() == PHASE_TPL)
+           bar();
 
-The building of SPL images can be enabled by CONFIG_SPL option in Kconfig.
+The building of xPL images can be enabled by CONFIG_SPL (etc.) options in
+Kconfig.
 
-Because SPL images normally have a different text base, one has to be
-configured by defining CONFIG_SPL_TEXT_BASE. The linker script has to be
-defined with CONFIG_SPL_LDSCRIPT.
+Because xPL images normally have a different text base, one has to be
+configured by defining CONFIG_xPL_TEXT_BASE. The linker script has to be
+defined with CONFIG_xPL_LDSCRIPT.
 
-To support generic U-Boot libraries and drivers in the SPL binary one can
-optionally define CONFIG_SPL_XXX_SUPPORT. Currently following options
+To support generic U-Boot libraries and drivers in the xPL binary one can
+optionally define CONFIG_xPL_XXX_SUPPORT. Currently following options
 are supported:
 
 CONFIG_SPL_LIBCOMMON_SUPPORT (common/libcommon.o)
@@ -75,7 +79,7 @@ CONFIG_SPL_DM_GPIO (drivers/gpio/gpio-uclass.o)
 CONFIG_SPL_BMP (drivers/video/bmp.o)
 CONFIG_SPL_BLOBLIST (common/bloblist.o)
 
-Adding SPL-specific code
+Adding xPL-specific code
 ------------------------
 
 To check whether a feature is enabled, use CONFIG_IS_ENABLED()::
@@ -90,7 +94,7 @@ U-Boot Boot Phases
 ------------------
 
 U-Boot goes through the following boot phases where TPL, VPL, SPL are optional.
-While many boards use SPL, less use TPL.
+While many boards use SPL, fewer use TPL.
 
 TPL
    Very early init, as tiny as possible. This loads SPL (or VPL if enabled).
@@ -117,7 +121,7 @@ Further usages of U-Boot SPL comprise:
 Checking the boot phase
 -----------------------
 
-Use `spl_phase()` to find the current U-Boot phase, e.g. `PHASE_SPL`. You can
+Use `xpl_phase()` to find the current U-Boot phase, e.g. `PHASE_SPL`. You can
 also find the previous and next phase and get the phase name.
 
 
@@ -177,29 +181,30 @@ files instead introduces another set of headaches.  These warnings are
 not usually important to understanding the flow, however.
 
 
-Reserving memory in SPL
+Reserving memory in xPL
 -----------------------
 
-If memory needs to be reserved in RAM during SPL stage with the requirement that
-the SPL reserved memory remains preserved across further boot stages too
+If memory needs to be reserved in RAM during an xPL phase with the requirement
+that the xPL reserved memory remains preserved across further boot phases too
 then it needs to be reserved mandatorily starting from end of RAM. This is to
-ensure that further stages can simply skip this region before carrying out
+ensure that further phases can simply skip this region before carrying out
 further reservations or updating the relocation address.
 
-Also out of these regions which are to be preserved across further stages of
+Also out of these regions which are to be preserved across further phases of
 boot, video framebuffer memory region must be reserved first starting from
-end of RAM for which helper function spl_reserve_video_from_ram_top is provided
-which makes sure that video memory is placed at top of reservation area with
+end of RAM for which the helper function spl_reserve_video_from_ram_top() is
+provided
+which makes sure that video memory is placed at the top of reservation area with
 further reservations below it.
 
-The corresponding information of reservation for those regions can be passed to
-further boot stages using a bloblist. For e.g. the information for
-framebuffer area reserved by SPL can be passed onto U-boot using
-BLOBLISTT_U_BOOT_VIDEO.
-
-The further boot stages need to parse each of the bloblist passed from SPL stage
-starting from video bloblist and skip this whole SPL reserved memory area from
-end of RAM as per the bloblists received, before carrying out further
-reservations or updating the relocation address. For e.g, U-boot proper uses
-function "setup_relocaddr_from_bloblist" to parse the bloblists passed from
-previous stage and skip the memory reserved from previous stage accordingly.
+The reservation information for these regions can be passed to the
+further boot phases using a bloblist. For e.g. the information for the
+framebuffer area reserved by xPL can be passed onto U-Boot using
+BLOBLISTT_U_BOOT_VIDEO
+
+The further boot phases need to parse each of the blobs passed from xPL phase
+starting from video bloblist and skip this whole xPL reserved-memory area from
+end of RAM as per the blobs received, before carrying out further
+reservations or updating the relocation address. For e.g, U-Boot proper uses
+function setup_relocaddr_from_bloblist() to parse the bloblist passed from
+previous phase and skip the memory reserved from previous phase accordingly.
diff --git a/doc/develop/tests_sandbox.rst b/doc/develop/tests_sandbox.rst
index 72923070150..0630180bc55 100644
--- a/doc/develop/tests_sandbox.rst
+++ b/doc/develop/tests_sandbox.rst
@@ -278,7 +278,7 @@ Whatever sandbox build is used, which tests are present is determined by which
 source files are built. For sandbox_spl, the of_platdata tests are built
 because of the build rule in test/dm/Makefile::
 
-   ifeq ($(CONFIG_SPL_BUILD),y)
+   ifeq ($(CONFIG_XPL_BUILD),y)
    obj-$(CONFIG_SPL_OF_PLATDATA) += of_platdata.o
    else
    ...other tests for non-spl
diff --git a/doc/develop/tests_writing.rst b/doc/develop/tests_writing.rst
index a328ebfef33..54efb7e1b04 100644
--- a/doc/develop/tests_writing.rst
+++ b/doc/develop/tests_writing.rst
@@ -321,15 +321,15 @@ to control that.
 Finally, add the test to the build by adding to the Makefile in the same
 directory::
 
-  obj-$(CONFIG_$(SPL_)CMDLINE) += wibble.o
+  obj-$(CONFIG_$(XPL_)CMDLINE) += wibble.o
 
 Note that CMDLINE is never enabled in SPL, so this test will only be present in
 U-Boot proper. See below for how to do SPL tests.
 
 As before, you can add an extra Kconfig check if needed::
 
-  ifneq ($(CONFIG_$(SPL_)WIBBLE),)
-  obj-$(CONFIG_$(SPL_)CMDLINE) += wibble.o
+  ifneq ($(CONFIG_$(XPL_)WIBBLE),)
+  obj-$(CONFIG_$(XPL_)CMDLINE) += wibble.o
   endif
 
 
diff --git a/doc/device-tree-bindings/bootph.yaml b/doc/device-tree-bindings/bootph.yaml
index a3ccf06efa7..a364b3fe37f 100644
--- a/doc/device-tree-bindings/bootph.yaml
+++ b/doc/device-tree-bindings/bootph.yaml
@@ -83,6 +83,6 @@ properties:
   bootph-all:
     type: boolean
     description:
-      Include this node in all phases (for U-Boot see enum u_boot_phase).
+      Include this node in all phases (for U-Boot see enum xpl_phase_t).
 
 additionalProperties: true