arch: xtensa: Refine HiFi sharing Kconfigs

Splits HiFi sharing into two different models.
 1. XTENSA_EAGER_HIFI_SHARING - unconditional save/restore
    of the HiFi registers when context switching
 2. XTENSA_LAZY_HIFI_SHARING - on demand save/restore of
    of the HiFi registers. If a thread does not use the
    HiFi registers, they are neither saved nor restored.

To maintain backwards compatibility, the eager model is the
default model when XTENSA_HIFI_SHARING is enabled.

Signed-off-by: Peter Mitsis <[email protected]>

Author: peter-mitsis

arch/Kconfig

@@ -1181,3 +1181,9 @@ config ARCH_HAS_CUSTOM_CURRENT_IMPL
 	help
 	  Select when architecture implements arch_current_thread() &
 	  arch_current_thread_set().
+
+config ARCH_IPI_LAZY_COPROCESSORS_SAVE
+	bool
+	help
+	  Select when the architecture has multi-CPU lazy context switching
+	  of coprocessor registers.

arch/xtensa/Kconfig

@@ -153,6 +153,34 @@ config XTENSA_HIFI_SHARING
 	  across context switches to allow multiple threads to perform
 	  concurrent HiFi operations.
 
+if XTENSA_HIFI_SHARING
+
+choice XTENSA_HIFI_SHARING_MODEL
+	prompt "Xtensa HiFi Sharing Model"
+	depends on XTENSA_HIFI_SHARING
+	default XTENSA_EAGER_HIFI_SHARING
+
+config XTENSA_EAGER_HIFI_SHARING
+	bool "Eager HiFi Sharing"
+	help
+	  This option enables eager sharing of HiFi registers across context
+	  switches. This means that the HiFi registers are unconditionally
+	  saved and restored on every context switch, allowing multiple threads
+	  to use HiFi instructions concurrently.
+
+config XTENSA_LAZY_HIFI_SHARING
+	bool "Lazy HiFi Sharing"
+	depends on SCHED_IPI_SUPPORTED || (MP_MAX_NUM_CPUS = 1)
+	select ARCH_IPI_LAZY_COPROCESSORS_SAVE
+	help
+	  This option enables lazy sharing of HiFi registers across context
+	  switches. This means that the HiFi registers are saved and restored
+	  only when a thread actually uses HiFi instructions, allowing for
+	  more efficient use of resources when HiFi instructions are not used.
+endchoice
+
+endif    # XTENSA_HIFI_SHARING
+
 endif    # XTENSA_CPU_HAS_HIFI
 
 endmenu  # Xtensa HiFi Options

arch/xtensa/core/CMakeLists.txt

@@ -29,7 +29,7 @@ zephyr_library_sources_ifdef(CONFIG_XTENSA_MPU mpu.c)
 zephyr_library_sources_ifdef(CONFIG_USERSPACE userspace.S syscall_helper.c)
 zephyr_library_sources_ifdef(CONFIG_LLEXT elf.c)
 zephyr_library_sources_ifdef(CONFIG_SMP smp.c)
-zephyr_library_sources_ifdef(CONFIG_XTENSA_HIFI_SHARING xtensa_hifi.S)
+zephyr_library_sources_ifdef(CONFIG_XTENSA_EAGER_HIFI_SHARING xtensa_hifi.S)
 
 zephyr_library_sources_ifdef(
   CONFIG_KERNEL_VM_USE_CUSTOM_MEM_RANGE_CHECK

arch/xtensa/core/offsets/offsets.c

@@ -61,7 +61,7 @@ GEN_OFFSET_SYM(_xtensa_irq_bsa_t, fpu14);
 GEN_OFFSET_SYM(_xtensa_irq_bsa_t, fpu15);
 #endif
 
-#if defined(CONFIG_XTENSA_HIFI_SHARING)
+#if defined(CONFIG_XTENSA_EAGER_HIFI_SHARING)
 GEN_OFFSET_SYM(_xtensa_irq_bsa_t, hifi);
 #endif
 

arch/xtensa/core/xtensa_asm2_util.S

@@ -185,7 +185,7 @@ _restore_ps_after:
 	FPU_REG_RESTORE
 #endif
 
-#if defined(CONFIG_XTENSA_HIFI_SHARING)
+#if defined(CONFIG_XTENSA_EAGER_HIFI_SHARING)
 .extern _xtensa_hifi_load
 	call0 _xtensa_hifi_load
 #endif
@@ -305,7 +305,7 @@ xtensa_switch:
 	movi a0, _switch_restore_pc
 	s32i a0, a1, ___xtensa_irq_bsa_t_pc_OFFSET
 
-#if defined(CONFIG_XTENSA_HIFI_SHARING)
+#if defined(CONFIG_XTENSA_EAGER_HIFI_SHARING)
 	call0 _xtensa_hifi_save
 #endif
 

arch/xtensa/include/xtensa_asm2_context.h

@@ -91,7 +91,7 @@
 # define _BSA_PADDING_FPU		(0)
 #endif
 
-#if defined(CONFIG_XTENSA_HIFI_SHARING)
+#if defined(CONFIG_XTENSA_EAGER_HIFI_SHARING)
 # define _BSA_PADDING_HIFI		(XCHAL_CP1_SA_SIZE + XCHAL_CP1_SA_ALIGN)
 #else
 # define _BSA_PADDING_HIFI		(0)
@@ -173,7 +173,7 @@ struct xtensa_irq_base_save_area {
 	uintptr_t fpu15;
 #endif
 
-#if defined(CONFIG_XTENSA_HIFI_SHARING)
+#if defined(CONFIG_XTENSA_EAGER_HIFI_SHARING)
 
 	/*
 	 * Carve space for the registers used by the HiFi audio engine

arch/xtensa/include/xtensa_asm2_s.h

@@ -17,7 +17,7 @@
  * only by the assembler.
  */
 
-#if defined(CONFIG_XTENSA_HIFI_SHARING)
+#if defined(CONFIG_XTENSA_EAGER_HIFI_SHARING)
 .extern _xtensa_hifi_save
 #endif
 
@@ -437,7 +437,7 @@ _xstack_returned_\@:
 	FPU_REG_SAVE
 #endif
 
-#if defined(CONFIG_XTENSA_HIFI_SHARING)
+#if defined(CONFIG_XTENSA_EAGER_HIFI_SHARING)
 	call0 _xtensa_hifi_save    /* Save HiFi registers */
 #endif