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armv8: make SPL exception vectors optional

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Even though the exception vector table is a fundamental part of the ARM
architecture, U-Boot mostly does not make real use of it, except when
crash dumping. But having it in takes up quite some space, partly due to
the architectural alignment requirement of 2KB. Since we don't take special
care of that, the compiler adds a more or less random amount of padding
space, which increases the image size quite a bit, especially for the SPL.

On a typical Allwinner build this is around 1.5KB of padding, plus 1KB
for the vector table (mostly padding space again), then some extra code
to do the actual handling. This amounts to almost 10% of the maximum image
size, which is quite a lot for a pure debugging feature.

Add a Kconfig symbol to allow the exception vector table to be left out
of the build for the SPL.
For now this is "default y" for everyone, but specific defconfigs,
platforms or .config files can opt out here at will, to mitigate the code
size pressure we see for some SPLs.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
This commit is contained in:
Andre Przywara 2018-07-25 00:57:01 +01:00 committed by Tom Rini
parent 15b6184971
commit 1416e2d225
3 changed files with 30 additions and 4 deletions
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11
arch/arm/cpu/armv8/Kconfig
View file

@ -1,5 +1,16 @@
if ARM64
config ARMV8_SPL_EXCEPTION_VECTORS
bool "Install crash dump exception vectors"
depends on SPL
default y
help
The default exception vector table is only used for the crash
dump, but still takes quite a lot of space in the image size.
Say N here if you are running out of code space in the image
and want to save some space at the cost of less debugging info.
config ARMV8_MULTIENTRY
bool "Enable multiple CPUs to enter into U-Boot"

4
arch/arm/cpu/armv8/Makefile
View file

@ -10,7 +10,11 @@ ifndef CONFIG_$(SPL_TPL_)TIMER
obj-$(CONFIG_SYS_ARCH_TIMER) += generic_timer.o
endif
obj-y += cache_v8.o
ifdef CONFIG_SPL_BUILD
obj-$(CONFIG_ARMV8_SPL_EXCEPTION_VECTORS) += exceptions.o
else
obj-y += exceptions.o
endif
obj-y += cache.o
obj-y += tlb.o
obj-y += transition.o

19
arch/arm/cpu/armv8/start.S
View file

@ -86,14 +86,23 @@ pie_fixup_done:
#ifdef CONFIG_SYS_RESET_SCTRL
bl reset_sctrl
#endif
#if defined(CONFIG_ARMV8__SPL_EXCEPTION_VECTORS) || !defined(CONFIG_SPL_BUILD)
.macro set_vbar, regname, reg
msr \regname, \reg
.endm
adr x0, vectors
#else
.macro set_vbar, regname, reg
.endm
#endif
/*
* Could be EL3/EL2/EL1, Initial State:
* Little Endian, MMU Disabled, i/dCache Disabled
*/
adr x0, vectors
switch_el x1, 3f, 2f, 1f
3: msr vbar_el3, x0
3: set_vbar vbar_el3, x0
mrs x0, scr_el3
orr x0, x0, #0xf /* SCR_EL3.NS|IRQ|FIQ|EA */
msr scr_el3, x0
@ -103,11 +112,11 @@ pie_fixup_done:
msr cntfrq_el0, x0 /* Initialize CNTFRQ */
#endif
b 0f
2: msr vbar_el2, x0
2: set_vbar vbar_el2, x0
mov x0, #0x33ff
msr cptr_el2, x0 /* Enable FP/SIMD */
b 0f
1: msr vbar_el1, x0
1: set_vbar vbar_el1, x0
mov x0, #3 << 20
msr cpacr_el1, x0 /* Enable FP/SIMD */
0:
@ -345,6 +354,7 @@ ENDPROC(smp_kick_all_cpus)
/*-----------------------------------------------------------------------*/
ENTRY(c_runtime_cpu_setup)
#if defined(CONFIG_ARMV8__SPL_EXCEPTION_VECTORS) || !defined(CONFIG_SPL_BUILD)
/* Relocate vBAR */
adr x0, vectors
switch_el x1, 3f, 2f, 1f
@ -354,6 +364,7 @@ ENTRY(c_runtime_cpu_setup)
b 0f
1: msr vbar_el1, x0
0:
#endif
ret
ENDPROC(c_runtime_cpu_setup)