Re[2]: [PATCH] powerpc 44x: support for 256KB PAGE_SIZE

=0D=0A Hello Milton,

 Thanks for reviewing. I'll re-post the updated patch shortly.

On Sunday, December 21, 2008 you wrote:

On Dec 19, 2008, at 12:39 AM, Yuri Tikhonov wrote:

quoted

This patch adds support for 256KB pages on ppc44x-based boards.

Hi.  A couple of small comments.

quoted

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index cd8ff7c..348702c 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig

@@ -436,6 +436,14 @@ config PPC_64K_PAGES
      bool "64k page size" if 44x || PPC_STD_MMU_64
      select PPC_HAS_HASH_64K if PPC_STD_MMU_64

+config PPC_256K_PAGES
+     bool "256k page size" if 44x
+     depends on !STDBINUTILS
+     help
+       ELF standard supports only page sizes up to 64K so you need a=20

patched
+       binutils in order to use 256K pages. Chose it only if you know w=

hat

quoted

+       you are doing.
+

Make the page size 256k.   As the ELF standard only requires alignment
to
support page sizes up to 64k, you will need to compile all of your user
space applications with a patched binutils.

Say N unless you know what you are doing.

(The previous text did not describe what the option actually did, and=20
did not emphasize that all of user space had to be compiled).

quoted

diff --git a/arch/powerpc/include/asm/thread_info.h=20

b/arch/powerpc/include/asm/thread_info.h
index 9665a26..3c8bbab 100644

--- a/arch/powerpc/include/asm/thread_info.h
+++ b/arch/powerpc/include/asm/thread_info.h

@@ -15,8 +15,12 @@
 #ifdef CONFIG_PPC64
 #define THREAD_SHIFT         14
 #else
+#ifdef CONFIG_PPC_256K_PAGES
+#define THREAD_SHIFT         15
+#else
 #define THREAD_SHIFT         13
 #endif
+#endif

Switching to #elif would remove the nested ifdef here.

quoted

 #define THREAD_SIZE          (1 << THREAD_SHIFT)

diff --git a/arch/powerpc/kernel/head_booke.h=20

b/arch/powerpc/kernel/head_booke.h
index fce2df9..bc6a26c 100644

--- a/arch/powerpc/kernel/head_booke.h
+++ b/arch/powerpc/kernel/head_booke.h

@@ -10,6 +10,14 @@
              mtspr   SPRN_IVOR##vector_number,r26;   \
              sync

+#ifndef CONFIG_PPC_256K_PAGES

This if should be on THREAD_SIZE or THREAD_SHIFT, not the option that=20
causes it to be large.

quoted

+#define ALLOC_STACK_FRAME(reg, val)  addi reg,reg,val
+#else
+#define ALLOC_STACK_FRAME(reg, val)                  \
+     addis   reg,reg,val@ha;                         \
+     addi    reg,reg,val@l
+#endif
+
 #define NORMAL_EXCEPTION_PROLOG                                        =

           \

quoted

      mtspr   SPRN_SPRG0,r10;         /* save two registers to work with=

 */\

quoted

      mtspr   SPRN_SPRG1,r11;                                           =

   \

quoted

@@ -20,7 +28,7 @@
      beq     1f;                                                       =

   \

quoted

      mfspr   r1,SPRN_SPRG3;          /* if from user, start at top of  =

 */\

quoted

      lwz     r1,THREAD_INFO-THREAD(r1); /* this thread's kernel stack  =

 */\

quoted

-     addi    r1,r1,THREAD_SIZE;                                        =

   \

quoted

+     ALLOC_STACK_FRAME(r1, THREAD_SIZE);                               =

   \

quoted

 1:   subi    r1,r1,INT_FRAME_SIZE;   /* Allocate an exception frame    =

 */\

quoted

      mr      r11,r1;                                                   =

   \

quoted

      stw     r10,_CCR(r11);          /* save various registers         =

 */\

quoted

diff --git a/init/Kconfig b/init/Kconfig
index f763762..96229b9 100644
--- a/init/Kconfig
+++ b/init/Kconfig

@@ -635,6 +635,16 @@ config ELF_CORE
      help
        Enable support for generating core dumps. Disabling saves about =

4k.

quoted

+config STDBINUTILS
+     bool "Using standard binutils" if EMBEDDED
+     depends on 44x
+     default y
+     help
+       Turning this option off allows you to select 256KB PAGE_SIZE on=

=20

quoted

44x.
+       Note, that kernel will be able to run only those applications,
+       which had been compiled using the patched binutils (ELF standard
+       supports only page sizes up to 64K).
+

The config variable 44x is pretty nondescript for a global config file.
  If you leave it here, I would suggest  making it depend on PPC && 44x
so that other people don't have to wonder what 44x means.  I didn't=20
look if there was a better place to put this option, somewhere=20
architecture specific might be better (eg after selecting the 44x cpu=20
type).

quoted

 config PCSPKR_PLATFORM
      bool "Enable PC-Speaker support" if EMBEDDED
      depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP ||=20
PPC_PSERIES

thanks,
milton

 Regards, Yuri

 --
 Yuri Tikhonov, Senior Software Engineer
 Emcraft Systems, www.emcraft.com