On Friday, August 25, 2017 1, Nicolas Pitre wrote:

This patch series provides the ability to store the kernel .data
segment compressed in ROM. It has to be copied to RAM anyway so
storing it uncompressed is arguably a waste of ROM resources.

While at it, the copying of .data (when not compressed) and the
clearing of .bss is performed using optimized string routines rather
than doing it one word at a time. And throw in small linker script
cleanups for good measure.

I like the idea, but unfortunately it won't build for my RZ/A1 
(CONFIG_ARCH_R7S72100=y) XIP system. It's a Cortex-A9 with MMU (meaning
you have to hack the Kconfig because apparently allowing
CONFIG_ARCH_MULTIPLATFORM=y and CONFIG_XIP_KERNEL=y in the same build
is considered a ridiculous thing to do).


  LD      vmlinux.o
  MODPOST vmlinux.o
  KSYM    .tmp_kallsyms1.o
  KSYM    .tmp_kallsyms2.o
  LD      vmlinux
  SORTEX  vmlinux
  SYSMAP  System.map
  XIPZ    arch/arm/boot/xipImage
data segment doesn't match end of xipImage
../arch/arm/boot/Makefile:46: recipe for target 'arch/arm/boot/xipImage' failed
make[2]: *** [arch/arm/boot/xipImage] Error 1
arch/arm/Makefile:334: recipe for target 'xipImage' failed
make[1]: *** [xipImage] Error 2
make[1]: Leaving directory '/home/renesas/tools/upstream/renesas-drivers/.out'
Makefile:145: recipe for target 'sub-make' failed
make: *** [sub-make] Error 2


I admit, I did not do any debug yet to find out why.
But if you want to see it, you can simply apply this patch below and 
then build the shmobile_defconfig (after you go in and enable XIP_KERNEL=y 
and XIP_DEFLATED_DATA=y of course).


---------------------------

diff --git a/arch/arm/Kconfigb/arch/arm/Kconfig
index 80191e93f09b..eeb4aa37e8e9 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig

@@ -338,7 +338,7 @@ config ARCH_MULTIPLATFORM
 	bool "Allow multiple platforms to be selected"
 	depends on MMU
 	select ARM_HAS_SG_CHAIN
-	select ARM_PATCH_PHYS_VIRT
+	select ARM_PATCH_PHYS_VIRT if !XIP_KERNEL
 	select AUTO_ZRELADDR
 	select TIMER_OF
 	select COMMON_CLK

@@ -1977,7 +1977,7 @@ endchoice
 
 config XIP_KERNEL
 	bool "Kernel Execute-In-Place from ROM"
-	depends on !ARM_LPAE && !ARCH_MULTIPLATFORM
+	depends on !ARM_LPAE
 	help
 	  Execute-In-Place allows the kernel to run from non-volatile storage
 	  directly addressable by the CPU, such as NOR flash. This saves RAM

Chris