#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
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);
* - 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
# 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
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
--- /dev/null
+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
" 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" \*/
projects / oweals / u-boot.git / commitdiff