--- /dev/null
+// crt0-app.S
+// Applications downloaded in RAM using a debug monitor (eg. XMON, RedBoot)
+// start here at _app_reset. Such applications don't have any vectors:
+// all exceptions are handled by the debug monitor.
+// Thus, this file essentially plays the role of the reset vector
+// to setup a few things before jumping to _start (in crt1*.S).
+
+// Copyright (c) 2005-2010 Tensilica Inc.
+//
+// Permission is hereby granted, free of charge, to any person obtaining
+// a copy of this software and associated documentation files (the
+// "Software"), to deal in the Software without restriction, including
+// without limitation the rights to use, copy, modify, merge, publish,
+// distribute, sublicense, and/or sell copies of the Software, and to
+// permit persons to whom the Software is furnished to do so, subject to
+// the following conditions:
+//
+// The above copyright notice and this permission notice shall be included
+// in all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+// IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+// CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+// TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+// SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+#include <xtensa/cacheattrasm.h>
+#include <xtensa/xt2000.h>
+#include <xtensa/coreasm.h>
+
+
+// Assumptions on entry to _app_reset:
+// - debug monitor handles all exceptions, has setup all vectors
+// - interrupt related state is initialized
+// (interrupts disabled or enabled for debug monitor's purposes)
+// - debug option related state is initialized (for debug monitor)
+// - any MMU related state is initialized (all handled by debug monitor)
+// - caches are initialized (cache attributes not necessarily correct)
+// - entire application is loaded (no unpacking needed here)
+
+// Assumptions on exit from _app_reset, ie. when jumping to _start:
+// - low (level-one) and medium priority interrupts are disabled
+// - C calling context not initialized:
+// - PS not fully initialized (eg. PS.WOE not set per ABI)
+// - SP not initialized
+// - the following are initialized:
+// - LITBASE, WindowBase, WindowStart, LCOUNT, CPENABLE, FP's FCR and FSR,
+// cache attributes
+
+/**************************************************************************/
+
+ .text
+ .global _app_reset
+_app_reset:
+ /* _app_reset may be required to be located at the beginning of the text
+ segment. However, the constant pool for _app_reset must be placed
+ before the code. Jump over the constant pool to solve this. */
+ j .LpastInitialConstants
+
+ .literal_position // tells the assembler/linker to place literals here
+
+.LpastInitialConstants:
+ // Keep a0 zero. It is used to initialize a few things.
+ // It is also the return address, where zero indicates
+ // that the frame used by _start is the bottommost frame.
+ //
+ movi a0, 0 // keep this register zero.
+
+#if XCHAL_HAVE_LOOPS
+ wsr a0, LCOUNT // loop count = 0
+#endif /* XCHAL_HAVE_LOOPS */
+
+ // Interrupts might be enabled, make sure at least medium and low priority
+ // interrupts are disabled until WindowBase, WindowStart, SP, and the stack
+ // are all properly setup (which will happen outside this file, after the
+ // _start label). We leave loops enabled on new exception architecture.
+#if XCHAL_HAVE_EXCEPTIONS
+ movi a2, XCHAL_EXCM_LEVEL
+ wsr a2, PS // set PS.INTLEVEL=EXCM_LEVEL, PS.WOE=0, PS.EXCM=0
+ rsync
+#endif
+
+ // DO THIS FIRST: initialize the window start and base
+ // before, so that windows don't move under us.
+#if XCHAL_HAVE_WINDOWED
+ // We do this even if we are assembling for the
+ // call0 abi, but it's not really needed.
+ movi a2, 1
+ wsr a2, WINDOWSTART // window start = 1
+ wsr a0, WINDOWBASE // window base = 0
+ rsync
+
+ // NOTE: a0 may no longer be zero here, because
+ // we wrote to WindowBase. So clear it again.
+ movi a0, 0
+#endif
+
+ // Now, BEFORE we do any L32R (or MOVI with non-immediate
+ // range which results in an L32R), ensure LITBASE is set
+ // correctly. This is necessary for RAM applications loaded
+ // using a target-side debug monitor -- such applications
+ // don't have a reset vector and start execution at _start.
+ // (This part is unnecessary if running from a reset vector.)
+ // The target-side debug monitor might have set LITBASE to
+ // anything at all, so we cannot rely on its value here.
+#if XCHAL_HAVE_ABSOLUTE_LITERALS
+ wsr a0, LITBASE // force PC-relative L32R
+ rsync
+# if XSHAL_USE_ABSOLUTE_LITERALS
+ .begin no-absolute-literals // use PC-rel L32R to load
+ movi a2, _lit4_start + 0x40001 // address of absolute literals
+ .end no-absolute-literals // (see handlers/ResetVector.S
+ wsr a2, LITBASE // for explanation)
+ rsync
+# endif
+#endif
+
+
+ /*
+ * Enable the caches correctly for this board.
+ * We use the "safe" sequence.
+ *
+ * NOTE: We don't *initialize* the caches here, because the
+ * target debugger agent (debug monitor) has initialized them for us.
+ */
+ movi a2, XTBOARD_CACHEATTR_DEFAULT
+ cacheattr_set /* set CACHEATTR from a2 (clobbers a3-a8) */
+
+
+
+ // Coprocessor option initialization
+#if XCHAL_HAVE_CP
+ //movi a2, XCHAL_CP_MASK // enable existing CPs
+ // To allow creating new coprocessors using TC that are not known
+ // at GUI build time without having to explicitly enable them,
+ // all CPENABLE bits must be set, even though they may not always
+ // correspond to a coprocessor.
+ movi a2, 0xFF // enable *all* bits, to allow dynamic TIE
+ wsr a2, CPENABLE
+#endif
+
+ // Floating point coprocessor option initialization
+#if XCHAL_HAVE_FP
+# define FCR 232 /* floating-point control register (user register number) */
+# define FSR 233 /* floating-point status register (user register number) */
+ rsync /* wait for WSR to CPENABLE to complete before accessing FP coproc state */
+ wur a0, FCR /* clear FCR (default rounding mode, round-nearest) */
+ wur a0, FSR /* clear FSR */
+#endif
+
+
+ /* NOTE: Future releases may clear BSS here rather than in the CRT1. */
+
+
+ /*
+ * Now jump to the application. This is typically the
+ * C run-time initialization ("CRT") which in turn calls main():
+ */
+ movi a4, _start
+ jx a4 // jump to _start
+
+ .size _app_reset, . - _app_reset
+
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