xtensa: add support for the xtensa processor architecture [2/2]

The Xtensa processor architecture is a configurable, extensible,
and synthesizable 32-bit RISC processor core provided by Tensilica, inc.

This is the second part of the basic architecture port, adding the
'arch/xtensa' directory and a readme file.

Signed-off-by: Chris Zankel <chris@zankel.net>
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>

1 files changed, 116 insertions, 0 deletions

diff --git a/arch/xtensa/cpu/u-boot.lds b/arch/xtensa/cpu/u-boot.lds
new file mode 100644
index 0000000000..853ae5a948
--- /dev/null
+++ b/arch/xtensa/cpu/u-boot.lds
@@ -0,0 +1,116 @@
+/*
+ * (C) Copyright 2008 - 2013 Tensilica, Inc.
+ * (C) Copyright 2014 - 2016 Cadence Design Systems Inc.
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <config.h>
+#include <asm/ldscript.h>
+#include <asm/arch/core.h>
+#include <asm/addrspace.h>
+#include <asm-offsets.h>
+
+OUTPUT_ARCH(xtensa)
+ENTRY(_start)
+
+/*
+ * U-Boot resets from SYSROM and unpacks itself from a ROM store to RAM.
+ * The reset vector is usually near the base of SYSROM and has room
+ * above it for the ROM store into which the rest of U-Boot is packed.
+ * The ROM store also needs to be above any other vectors that are in ROM.
+ * If a core has its vectors near the top of ROM, this must be edited.
+ *
+ * Note that to run C code out of ROM, the processor would have to support
+ * 'relocatable' exception vectors and provide a scratch memory for the
+ * initial stack. Not all Xtensa processor configurations support that, so
+ * we can simplify the boot process and unpack U-Boot to RAM immediately.
+ * This, however, requires that memory have been initialized throug some
+ * other means (serial ROM, for example) or are initialized early (requiring
+ * an assembler function. See start.S for more details)
+ */
+
+SECTIONS
+{
+  . = + SIZEOF_HEADERS;
+  SECTION_ResetVector(XCHAL_RESET_VECTOR_VADDR, LMA_EQ_VMA)
+
+  .reloc_table ALIGN(4) : FOLLOWING(.ResetVector.text)
+  {
+    __reloc_table_start = ABSOLUTE(.);
+#if XCHAL_HAVE_WINDOWED
+    RELOCATE2(WindowVectors,text);
+#endif
+    RELOCATE2(KernelExceptionVector,literal);
+    RELOCATE2(KernelExceptionVector,text);
+    RELOCATE2(UserExceptionVector,literal);
+    RELOCATE2(UserExceptionVector,text);
+    RELOCATE2(DoubleExceptionVector,literal);
+    RELOCATE2(DoubleExceptionVector,text);
+    RELOCATE1(text);
+    RELOCATE1(rodata);
+    RELOCATE1(data);
+    RELOCATE1(u_boot_list);
+    __reloc_table_end = ABSOLUTE(.);
+  }
+
+#if XCHAL_HAVE_WINDOWED
+  SECTION_VECTOR(WindowVectors,text,XCHAL_WINDOW_VECTORS_VADDR,
+		 FOLLOWING(.reloc_table))
+  SECTION_VECTOR(KernelExceptionVector,literal,XCHAL_KERNEL_VECTOR_VADDR-8,
+		 FOLLOWING(.WindowVectors.text))
+#else
+  SECTION_VECTOR(KernelExceptionVector,literal,XCHAL_KERNEL_VECTOR_VADDR-8,
+		 FOLLOWING(.reloc_table))
+#endif
+  SECTION_VECTOR(KernelExceptionVector,text,XCHAL_KERNEL_VECTOR_VADDR,
+		 FOLLOWING(.KernelExceptionVector.literal))
+  SECTION_VECTOR(UserExceptionVector,literal,XCHAL_USER_VECTOR_VADDR-8,
+		 FOLLOWING(.KernelExceptionVector.text))
+  SECTION_VECTOR(UserExceptionVector,text,XCHAL_USER_VECTOR_VADDR,
+		 FOLLOWING(.UserExceptionVector.literal))
+  SECTION_VECTOR(DoubleExceptionVector,literal,XCHAL_DOUBLEEXC_VECTOR_VADDR-8,
+		 FOLLOWING(.UserExceptionVector.text))
+  SECTION_VECTOR(DoubleExceptionVector,text,XCHAL_DOUBLEEXC_VECTOR_VADDR,
+		 FOLLOWING(.DoubleExceptionVector.literal))
+
+  __monitor_start = CONFIG_SYS_TEXT_ADDR;
+
+  SECTION_text(CONFIG_SYS_TEXT_ADDR, FOLLOWING(.DoubleExceptionVector.text))
+  SECTION_rodata(ALIGN(16), FOLLOWING(.text))
+  SECTION_u_boot_list(ALIGN(16), FOLLOWING(.rodata))
+  SECTION_data(ALIGN(16), FOLLOWING(.u_boot_list))
+
+  __reloc_end = .;
+  __init_end = .;
+
+  SECTION_bss(__init_end (OVERLAY),)
+
+  __monitor_end = .;
+
+  /*
+   * On many Xtensa boards a region of RAM may be mapped to the ROM address
+   * space to facilitate on-chip-debug, and U-Boot must fit with that region.
+   * The config variables CONFIG_SYS_MONITOR_* define the region.
+   * If U-Boot extends beyond this region it will appear discontiguous in the
+   * address space and is in danger of overwriting itself during unpacking
+   * ("relocation").
+   * This causes U-Boot to crash in a way that is difficult to debug. On some
+   * boards (such as xtav60) the region is small enough that U-Boot will not
+   * fit if compiled entirely with -O0 (a common scenario). To avoid a lengthy
+   * debugging session when this happens, ensure a link-time error occurs.
+   *
+   */
+
+   ASSERT(__monitor_end - __monitor_start <= CONFIG_SYS_MONITOR_LEN,
+          "U-Boot ROM image is too large. Check optimization level.")
+
+  SECTION_xtensa
+  SECTION_debug
+
+  /DISCARD/ : { *(.dynstr*) }
+  /DISCARD/ : { *(.hash*) }
+  /DISCARD/ : { *(.interp) }
+  /DISCARD/ : { *(.got*) }
+  /DISCARD/ : { *(.dynsym) }
+}