Applied to: git://git.denx.de/u-boot-nios.git next
Thanks, --Scott
Thomas Chou wrote:
The "-ffixed-r15" option doesn't work well for gcc4. Since we don't use gp for small data with option "-G0", we can use gp as global data pointer. This allows compiler to use r15. It is necessary for gcc4 to work properly.
Signed-off-by: Thomas Chou thomas@wytron.com.tw
v2: update standalone stubs and doc.
README | 8 ++++++++ arch/nios2/config.mk | 2 +- arch/nios2/cpu/start.S | 7 ------- arch/nios2/include/asm/global_data.h | 2 +- doc/README.standalone | 13 +++++++------ examples/standalone/stubs.c | 6 +++--- 6 files changed, 20 insertions(+), 18 deletions(-)
diff --git a/README b/README index 81692c0..acb3308 100644 --- a/README +++ b/README @@ -4023,6 +4023,14 @@ On ARM, the following registers are used:
==> U-Boot will use R8 to hold a pointer to the global data+On Nios II, the ABI is documented here:
- http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
- ==> U-Boot will use gp to hold a pointer to the global data
- Note: on Nios II, we give "-G0" option to gcc and don't use gp
- to access small data sections, so gp is free.
NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope, or current versions of GCC may "optimize" the code too much.
diff --git a/arch/nios2/config.mk b/arch/nios2/config.mk index 8e5d6ef..6789038 100644 --- a/arch/nios2/config.mk +++ b/arch/nios2/config.mk @@ -27,6 +27,6 @@ CROSS_COMPILE ?= nios2-elf- STANDALONE_LOAD_ADDR = 0x02000000 -L $(gcclibdir)
PLATFORM_CPPFLAGS += -DCONFIG_NIOS2 -D__NIOS2__ -PLATFORM_CPPFLAGS += -ffixed-r15 -G0 +PLATFORM_CPPFLAGS += -G0
LDSCRIPT ?= $(SRCTREE)/$(CPUDIR)/u-boot.lds diff --git a/arch/nios2/cpu/start.S b/arch/nios2/cpu/start.S index d1016ea..76d3b52 100644 --- a/arch/nios2/cpu/start.S +++ b/arch/nios2/cpu/start.S @@ -113,13 +113,6 @@ _cur: movhi r5, %hi(_cur - _start) bne r5, r6, 4b 5:
- /* GLOBAL POINTER -- the global pointer is used to reference
* "small data" (see -G switch). The linker script must* provide the gp address.*/movhi gp, %hi(_gp)ori gp, gp, %lo(_gp)- /* JUMP TO RELOC ADDR */ movhi r4, %hi(_reloc) ori r4, r4, %lo(_reloc)
diff --git a/arch/nios2/include/asm/global_data.h b/arch/nios2/include/asm/global_data.h index 34aa962..f1b3482 100644 --- a/arch/nios2/include/asm/global_data.h +++ b/arch/nios2/include/asm/global_data.h @@ -48,6 +48,6 @@ typedef struct global_data { #define GD_FLG_LOGINIT 0x00020 /* Log Buffer has been initialized */ #define GD_FLG_DISABLE_CONSOLE 0x00040 /* Disable console (in & out) */
-#define DECLARE_GLOBAL_DATA_PTR register gd_t *gd asm ("r15") +#define DECLARE_GLOBAL_DATA_PTR register gd_t *gd asm ("gp")
#endif /* __ASM_NIOS2_GLOBALDATA_H_ */ diff --git a/doc/README.standalone b/doc/README.standalone index 885c92f..6381087 100644 --- a/doc/README.standalone +++ b/doc/README.standalone @@ -19,12 +19,12 @@ Design Notes on Exporting U-Boot Functions to Standalone Applications: thus the compiler cannot perform type checks on these assignments.
- The pointer to the jump table is passed to the application in a
- machine-dependent way. PowerPC, ARM, MIPS and Blackfin architectures
- use a dedicated register to hold the pointer to the 'global_data'
- structure: r2 on PowerPC, r8 on ARM, k0 on MIPS, and P3 on Blackfin.
- The x86 architecture does not use such a register; instead, the
- pointer to the 'global_data' structure is passed as 'argv[-1]'
- pointer.
machine-dependent way. PowerPC, ARM, MIPS, Blackfin and Nios II
architectures use a dedicated register to hold the pointer to the
'global_data' structure: r2 on PowerPC, r8 on ARM, k0 on MIPS,
P3 on Blackfin and gp on Nios II. The x86 architecture does not
use such a register; instead, the pointer to the 'global_data'
structure is passed as 'argv[-1]' pointer.
The application can access the 'global_data' structure in the same way as U-Boot does:
@@ -56,6 +56,7 @@ Design Notes on Exporting U-Boot Functions to Standalone Applications: ARM 0x0c100000 0x0c100000 MIPS 0x80200000 0x80200000 Blackfin 0x00001000 0x00001000
Nios II 0x02000000 0x02000000
For example, the "hello world" application may be loaded and executed on a PowerPC board with the following commands:
diff --git a/examples/standalone/stubs.c b/examples/standalone/stubs.c index ce3371d..0187708 100644 --- a/examples/standalone/stubs.c +++ b/examples/standalone/stubs.c @@ -84,7 +84,7 @@ gd_t *global_data; : : "i"(offsetof(gd_t, jt)), "i"(XF_ ## x) : "r0"); #elif defined(CONFIG_NIOS2) /*
- r15 holds the pointer to the global_data, r8 is call-clobbered
*/
- gp holds the pointer to the global_data, r8 is call-clobbered
#define EXPORT_FUNC(x) \ asm volatile ( \ @@ -92,11 +92,11 @@ gd_t *global_data; #x ":\n" \ " movhi r8, %%hi(%0)\n" \ " ori r8, r0, %%lo(%0)\n" \ -" add r8, r8, r15\n" \ +" add r8, r8, gp\n" \ " ldw r8, 0(r8)\n" \ " ldw r8, %1(r8)\n" \ " jmp r8\n" \
- : : "i"(offsetof(gd_t, jt)), "i"(XF_ ## x * sizeof(void *)) : "r15");
- : : "i"(offsetof(gd_t, jt)), "i"(XF_ ## x * sizeof(void *)) : "gp");
#elif defined(CONFIG_M68K) /*
- d7 holds the pointer to the global_data, a0 is a call-clobbered