From: Chris Zankel chris@zankel.net
The Xtensa processor architecture is a configurable, extensible, and synthesizable 32-bit RISC processor core provided by Cadence.
This is the first part of the basic architecture port with changes to common files. The 'arch/xtensa' directory, and boards and additional drivers will be in separate commits.
Signed-off-by: Chris Zankel chris@zankel.net Signed-off-by: Max Filippov jcmvbkbc@gmail.com --- Changes v2->v3: - drop changes to the MAKEALL script; - refactor do_bdinfo; - fix wording of doc/README.xtensa; - rewrite memory exception handling part in doc/README.xtensa. - add bss clearing call to init_sequence_f; --- MAINTAINERS | 5 +++ Makefile | 10 ++++- cmd/bdinfo.c | 8 ++++ common/board_f.c | 12 ++++-- common/image.c | 1 + doc/README.xtensa | 97 +++++++++++++++++++++++++++++++++++++++++++++ examples/standalone/stubs.c | 47 ++++++++++++++++++++++ include/image.h | 1 + include/linux/stat.h | 4 +- 9 files changed, 179 insertions(+), 6 deletions(-) create mode 100644 doc/README.xtensa
diff --git a/MAINTAINERS b/MAINTAINERS index 1db8243..24afa88 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -453,6 +453,11 @@ S: Maintained T: git git://git.denx.de/u-boot-x86.git F: arch/x86/
+XTENSA +M: Max Filippov jcmvbkbc@gmail.com +S: Maintained +F: arch/xtensa/ + THE REST M: Tom Rini trini@konsulko.com L: u-boot@lists.denx.de diff --git a/Makefile b/Makefile index bccfbaa..7935d19 100644 --- a/Makefile +++ b/Makefile @@ -557,6 +557,14 @@ else include/config/auto.conf: ; endif # $(dot-config)
+# +# Xtensa linker script cannot be preprocessed with -ansi because of +# preprocessor operations on strings that don't make C identifiers. +# +ifeq ($(CONFIG_XTENSA),) +LDPPFLAGS += -ansi +endif + ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE KBUILD_CFLAGS += -Os else @@ -1311,7 +1319,7 @@ $(timestamp_h): $(srctree)/Makefile FORCE
# --------------------------------------------------------------------------- quiet_cmd_cpp_lds = LDS $@ -cmd_cpp_lds = $(CPP) -Wp,-MD,$(depfile) $(cpp_flags) $(LDPPFLAGS) -ansi \ +cmd_cpp_lds = $(CPP) -Wp,-MD,$(depfile) $(cpp_flags) $(LDPPFLAGS) \ -D__ASSEMBLY__ -x assembler-with-cpp -P -o $@ $<
u-boot.lds: $(LDSCRIPT) prepare FORCE diff --git a/cmd/bdinfo.c b/cmd/bdinfo.c index e1128cb..fb76f35 100644 --- a/cmd/bdinfo.c +++ b/cmd/bdinfo.c @@ -519,6 +519,14 @@ int do_bdinfo(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[]) return 0; }
+#elif defined(CONFIG_XTENSA) + +int do_bdinfo(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[]) +{ + print_std_bdinfo(gd->bd); + return 0; +} + #else #error "a case for this architecture does not exist!" #endif diff --git a/common/board_f.c b/common/board_f.c index c4501af..da381db 100644 --- a/common/board_f.c +++ b/common/board_f.c @@ -54,6 +54,8 @@ #include <asm/sections.h> #if defined(CONFIG_X86) || defined(CONFIG_ARC) #include <asm/init_helpers.h> +#endif +#if defined(CONFIG_X86) || defined(CONFIG_ARC) || defined(CONFIG_XTENSA) #include <asm/relocate.h> #endif #ifdef CONFIG_SANDBOX @@ -271,7 +273,8 @@ static int setup_mon_len(void) gd->mon_len = (ulong)&__bss_end - (ulong)_start; #elif defined(CONFIG_SANDBOX) || defined(CONFIG_EFI_APP) gd->mon_len = (ulong)&_end - (ulong)_init; -#elif defined(CONFIG_BLACKFIN) || defined(CONFIG_NIOS2) +#elif defined(CONFIG_BLACKFIN) || defined(CONFIG_NIOS2) || \ + defined(CONFIG_XTENSA) gd->mon_len = CONFIG_SYS_MONITOR_LEN; #elif defined(CONFIG_NDS32) gd->mon_len = (ulong)(&__bss_end) - (ulong)(&_start); @@ -971,7 +974,7 @@ static init_fnc_t init_sequence_f[] = { * - board info struct */ setup_dest_addr, -#if defined(CONFIG_BLACKFIN) +#if defined(CONFIG_BLACKFIN) || defined(CONFIG_XTENSA) /* Blackfin u-boot monitor should be on top of the ram */ reserve_uboot, #endif @@ -1003,7 +1006,7 @@ static init_fnc_t init_sequence_f[] = { # endif #endif /* CONFIG_DM_VIDEO */ reserve_trace, -#if !defined(CONFIG_BLACKFIN) +#if !defined(CONFIG_BLACKFIN) && !defined(CONFIG_XTENSA) reserve_uboot, #endif #ifndef CONFIG_SPL_BUILD @@ -1036,6 +1039,9 @@ static init_fnc_t init_sequence_f[] = { clear_bss, do_elf_reloc_fixups, #endif +#if defined(CONFIG_XTENSA) + clear_bss, +#endif #if !defined(CONFIG_ARM) && !defined(CONFIG_SANDBOX) jump_to_copy, #endif diff --git a/common/image.c b/common/image.c index af155b2..7ad04ca 100644 --- a/common/image.c +++ b/common/image.c @@ -93,6 +93,7 @@ static const table_entry_t uimage_arch[] = { { IH_ARCH_ARM64, "arm64", "AArch64", }, { IH_ARCH_ARC, "arc", "ARC", }, { IH_ARCH_X86_64, "x86_64", "AMD x86_64", }, + { IH_ARCH_XTENSA, "xtensa", "Xtensa", }, { -1, "", "", }, };
diff --git a/doc/README.xtensa b/doc/README.xtensa new file mode 100644 index 0000000..4068582 --- /dev/null +++ b/doc/README.xtensa @@ -0,0 +1,97 @@ +U-Boot for the Xtensa Architecture +================================== + +Xtensa Architecture and Diamond Cores +------------------------------------- + +Xtensa is a configurable processor architecture from Tensilica, Inc. +Diamond Cores are pre-configured instances available for license and +SoC cores in the same manner as ARM, MIPS, etc. + +Xtensa licensees create their own Xtensa cores with selected features +and custom instructions, registers and co-processors. The custom core +is configured with Tensilica tools and built with Tensilica's Xtensa +Processor Generator. + +There are an effectively infinite number of CPUs in the Xtensa +architecture family. It is, however, not feasible to support individual +Xtensa CPUs in U-Boot. Therefore, there is only a single 'xtensa' CPU +in the cpu tree of U-Boot. + +In the same manner as the Linux port to Xtensa, U-Boot adapts to an +individual Xtensa core configuration using a set of macros provided with +the particular core. This is part of what is known as the hardware +abstraction layer (HAL). For the purpose of U-Boot, the HAL consists only +of a few header files. These provide CPP macros that customize sources, +Makefiles, and the linker script. + + +Adding support for an additional processor configuration +-------------------------------------------------------- + +The header files for one particular processor configuration are inside +a variant-specific directory located in the arch/xtensa/include/asm +directory. The name of that directory starts with 'arch-' followed by +the name for the processor configuration, for example, arch-dc233c for +the Diamond DC233 processor. + + core.h Definitions for the core itself. + +The following files are part of the overlay but not used by U-Boot. + + tie.h Co-processors and custom extensions defined + in the Tensilica Instruction Extension (TIE) + language. + tie-asm.h Assembly macros to access custom-defined registers + and states. + + +Global Data Pointer, Exported Function Stubs, and the ABI +--------------------------------------------------------- + +To support standalone applications launched with the "go" command, +U-Boot provides a jump table of entrypoints to exported functions +(grep for EXPORT_FUNC). The implementation for Xtensa depends on +which ABI (or function calling convention) is used. + +Windowed ABI presents unique difficulties with the approach based on +keeping global data pointer in dedicated register. Because the register +window rotates during a call, there is no register that is constantly +available for the gd pointer. Therefore, on xtensa gd is a simple +global variable. Another difficulty arises from the requirement to have +an 'entry' at the beginning of a function, which rotates the register +file and reserves a stack frame. This is an integral part of the +windowed ABI implemented in hardware. It makes using a jump table to an +arbitrary (separately compiled) function a bit tricky. Use of a simple +wrapper is also very tedious due to the need to move all possible +register arguments and adjust the stack to handle arguments that cannot +be passed in registers. The most efficient approach is to have the jump +table perform the 'entry' so as to pretend it's the start of the real +function. This requires decoding the target function's 'entry' +instruction to determine the stack frame size, and adjusting the stack +pointer accordingly, then jumping into the target function just after +the 'entry'. Decoding depends on the processor's endianness so uses the +HAL. The implementation (12 instructions) is in examples/stubs.c. + + +Access to Invalid Memory Addresses +---------------------------------- + +U-Boot does not check if memory addresses given as arguments to commands +such as "md" are valid. There are two possible types of invalid +addresses: an area of physical address space may not be mapped to RAM +or peripherals, or in the presence of MMU an area of virtual address +space may not be mapped to physical addresses. + +Accessing first type of invalid addresses may result in hardware lockup, +reading of meaningless data, written data being ignored or an exception, +depending on the CPU wiring to the system. Accessing second type of +invalid addresses always ends with an exception. + +U-Boot for Xtensa provides a special memory exception handler that +reports such access attempts and resets the board. + + +------------------------------------------------------------------------------ +Chris Zankel +Ross Morley diff --git a/examples/standalone/stubs.c b/examples/standalone/stubs.c index 0d62067..a8b7e14 100644 --- a/examples/standalone/stubs.c +++ b/examples/standalone/stubs.c @@ -240,6 +240,53 @@ gd_t *global_data; " ld r10, [r10, %1]\n" \ " j [r10]\n" \ : : "i"(offsetof(gd_t, jt)), "i"(FO(x)) : "r10"); +#elif defined(CONFIG_XTENSA) +/* + * Global data ptr is in global_data, jump table ptr is in jt. + * Windowed ABI: Jump just past 'entry' in target and adjust stack frame + * (extract stack frame size from target 'entry' instruction). + */ + +static void **jt; + +#if defined(__XTENSA_CALL0_ABI__) +#define EXPORT_FUNC(f, a, x, ...) \ + asm volatile ( \ +" .extern jt\n" \ +" .globl " #x "\n" \ +" .align 4\n" \ +#x ":\n" \ +" l32i a8, %0, 0\n" \ +" l32i a8, a8, %1\n" \ +" jx a8\n" \ + : : "r"(jt), "i" (FO(x)) : "a8"); +#elif defined(__XTENSA_WINDOWED_ABI__) +#if XCHAL_HAVE_BE +# define SFT "8" +#else +# define SFT "12" +#endif +#define EXPORT_FUNC(f, a, x, ...) \ + asm volatile ( \ +" .extern jt\n" \ +" .globl " #x "\n" \ +" .align 4\n" \ +#x ":\n" \ +" entry sp, 16\n" \ +" l32i a8, %0, 0\n" \ +" l32i a8, a8, %1\n" \ +" l32i a9, a8, 0\n" \ +" extui a9, a9, " SFT ", 12\n" \ +" subx8 a9, a9, sp\n" \ +" movi a10, 16\n" \ +" sub a9, a10, a9\n" \ +" movsp sp, a9\n" \ +" addi a8, a8, 3\n" \ +" jx a8\n" \ + : : "r"(jt), "i" (FO(x)) : "a8", "a9", "a10"); +#else +#error Unsupported Xtensa ABI +#endif #else /*" addi $sp, $sp, -24\n" \ " br $r16\n" */ diff --git a/include/image.h b/include/image.h index 734def3..64da722 100644 --- a/include/image.h +++ b/include/image.h @@ -200,6 +200,7 @@ enum { IH_ARCH_ARM64, /* ARM64 */ IH_ARCH_ARC, /* Synopsys DesignWare ARC */ IH_ARCH_X86_64, /* AMD x86_64, Intel and Via */ + IH_ARCH_XTENSA, /* Xtensa */
IH_ARCH_COUNT, }; diff --git a/include/linux/stat.h b/include/linux/stat.h index cef6369..1af0876 100644 --- a/include/linux/stat.h +++ b/include/linux/stat.h @@ -126,7 +126,7 @@ struct stat {
#endif /* __MIPS__ */
-#if defined(__AVR32__) || defined(__SH__) +#if defined(__AVR32__) || defined(__SH__) || defined(__XTENSA__)
struct stat { unsigned long st_dev; @@ -149,7 +149,7 @@ struct stat { unsigned long __unused5; };
-#endif /* __AVR32__ || __SH__ */ +#endif /* __AVR32__ || __SH__ || __XTENSA__ */
#ifdef __cplusplus }