U-Boot-V2: ARM: introduce CONFIG_SKIP_RELOCATION

Introduce CONFIG_SKIP_RELOCATION as alternative define. This may be desired in some conditions where U-Boot is downloaded directly into SRAM during NAND/Peripheral download mode and is not expected to be relocated.

This patch also organizes SKIP_LOWLEVEL_INIT and SKIP_RELOCATION in a common arm feature dependent section.

(quoted diff) +7 -0

+config SKIP_LOWLEVEL_INIT
+	bool
+	default n
+	depends on ARM
+	prompt "Skip lowlevel init"
+	help
+	  This entry skips the SDRAM initialising on many ARM based

boards.

Introduce CONFIG_SKIP_RELOCATION as alternative define. This may be desired in some conditions where U-Boot is downloaded directly into SRAM during NAND/Peripheral download mode and is not expected to be relocated.

This patch also organizes SKIP_LOWLEVEL_INIT and SKIP_RELOCATION in a common arm feature dependent section.

Signed-off-by Nishanth Menon <[email protected]>

Index: u-boot-v2.git/arch/arm/cpu/start-arm.S
===================================================================
--- u-boot-v2.git.orig/arch/arm/cpu/start-arm.S 2008-05-05
09:35:00.000000000 -0500
+++ u-boot-v2.git/arch/arm/cpu/start-arm.S 2008-05-05
09:35:05.000000000 -0500

(quoted diff) +4 -0

@@ -160,6 +160,10 @@
 	bl	board_init_lowlevel
 #endif
 
+	/*
+	 * In some circumstances, we may choose not to relocate u-boot
+	 */
+#ifndef CONFIG_SKIP_RELOCATION
 relocate:				/* relocate U-Boot to RAM
 */
 	adr	r0, _start		/* r0 <- current position of

code */
ldr r1, _TEXT_BASE /* test if we run from flash or
RAM */

(quoted diff) +1 -0

@@ -176,6 +180,7 @@
 	stmia	r1!, {r3-r10}		/* copy to   target address [r1]
 */
 	cmp	r0, r2			/* until source end addreee [r2]
 */
 	ble	copy_loop
+#endif
 

/* Set up the stack
*/
stack_setup:
Index: u-boot-v2.git/arch/arm/Kconfig
===================================================================
--- u-boot-v2.git.orig/arch/arm/Kconfig 2008-05-05 09:34:44.000000000
-0500
+++ u-boot-v2.git/arch/arm/Kconfig 2008-05-05 09:35:25.000000000
-0500

(quoted diff) +1 -0

@@ -74,6 +74,7 @@
 	bool
 	select ARM926EJS
 
+
 choice
 	prompt "Select your board"
 

@@ -140,7 +141,7 @@
 	  The i.MX SoCs have a Pin which can output different reference

frequencies.
Say y here if you want to have the clko command which lets you
select the

(quoted diff) +10 -1

 	  frequency to output on this pin.
-	  
+
 source arch/arm/mach-netx/Kconfig
 
 menu "Arm specific settings         "

@@ -164,6 +165,27 @@
 	  If you want to start a 2.6 kernel and use an
 	  initrd image say y here.
 
+menu "Boot Features"
+
+config SKIP_LOWLEVEL_INIT
+	bool
+	default n
+	depends on ARM
+	prompt "Skip lowlevel init"
+	help
+	  This entry skips the SDRAM initialising on many ARM based

boards.

(quoted diff) +12 -0

+	  It enables using U-boot as a second stage bootloader.
+
+config SKIP_RELOCATION
+	bool
+	default n
+	depends on ARM
+	prompt "Skip U-Boot Relocation"
+	help
+	  This entry skips the relocation logic on certain platforms
+	  It enables using U-boot as a second stage bootloader.
+endmenu
+
 endmenu
 
 source common/Kconfig

Index: u-boot-v2.git/common/Kconfig
===================================================================
--- u-boot-v2.git.orig/common/Kconfig 2008-05-05 09:34:44.000000000
-0500
+++ u-boot-v2.git/common/Kconfig 2008-05-05 09:35:05.000000000
-0500

(quoted diff) +0 -6

@@ -216,14 +216,6 @@
 	help
 	  Enable build of u-boot with -g.
 
-config SKIP_LOWLEVEL_INIT
-	bool
-	depends on ARM
-	prompt "Skip lowlevel init"
-	help
-	  This entry skips the SDRAM initialising on many ARM based

boards.

(quoted diff) +0 -2

-	  It enables using U-boot as a second stage bootloader.
-
 config ENABLE_FLASH_NOISE
 	bool
 	prompt "verbose flash handling"

-----Original Message-----
From: Sascha Hauer [mailto:s.hauer at pengutronix.de]
Sent: Wednesday, May 07, 2008 8:51 AM
To: Menon, Nishanth
Cc: u-boot-users at lists.sourceforge.net
Subject: Re: [Patch 2/4] U-Boot-V2: ARM: introduce CONFIG_SKIP_RELOCATION

Quoted 4 lines · Nishanth

Introduce CONFIG_SKIP_RELOCATION as alternative define. This may be desired in some conditions where U-Boot is downloaded directly into SRAM during NAND/Peripheral download mode and is not expected to be relocated.

If U-Boot is not expected to be relocated, TEXT_BASE should be in SRAM in which case the relocation loop just does nothing. So you end up in saving 12 * 4 bytes of space. Is it really worth to introduce an #ifdef for such a small saving?

Sascha,

Quoted 13 lines

-----Original Message-----
From: Sascha Hauer [mailto:s.hauer at pengutronix.de]
Sent: Wednesday, May 07, 2008 8:51 AM
To: Menon, Nishanth
Cc: u-boot-users at lists.sourceforge.net
Subject: Re: [Patch 2/4] U-Boot-V2: ARM: introduce CONFIG_SKIP_RELOCATION

Quoted 4 lines · Nishanth

Introduce CONFIG_SKIP_RELOCATION as alternative define. This may be desired in some conditions where U-Boot is downloaded directly into SRAM during NAND/Peripheral download mode and is not expected to be relocated.

Quoted 4 lines

If U-Boot is not expected to be relocated, TEXT_BASE should be in SRAM in which case the relocation loop just does nothing. So you end up in saving 12 * 4 bytes of space. Is it really worth to introduce an #ifdef for such a small saving?

Probably not much of a saving, been looking at the code, and I see CONFIG_RELOCATABLE depending on ppc. It may not be just the savings part of 48bytes. There can be additional stuff an SOC might choose to do. (ppc start.S also uses the define to save 4 instructions or so). Cleaner approach might make sense to remove the CONFIG_RELOCATABLE dependency on ppc and make it a global configuration. Allowing any platform to choose what ever it wants to do.

-----Original Message-----
From: Sascha Hauer [mailto:s.hauer at pengutronix.de]
Sent: Wednesday, May 07, 2008 10:29 AM
To: Menon, Nishanth
Cc: u-boot-users at lists.sourceforge.net
Subject: Re: [Patch 2/4] U-Boot-V2: ARM: introduce CONFIG_SKIP_RELOCATION

CONFIG_RELOCATABLE on powerpc means something different. On arm we start U-Boot by running it at an address != link address and _copy_ (not relocate) ourselves to the address we are linked at. On powerpc real relocation is done if CONFIG_RELOCATABLE is enabled.
Hence the option you wanted to add should better have the name CONFIG_SKIP_COPY_TO_SDRAM or something like that.

Sascha,

Quoted 7 lines

-----Original Message-----
From: Sascha Hauer [mailto:s.hauer at pengutronix.de]
Sent: Wednesday, May 07, 2008 10:29 AM
To: Menon, Nishanth
Cc: u-boot-users at lists.sourceforge.net
Subject: Re: [Patch 2/4] U-Boot-V2: ARM: introduce CONFIG_SKIP_RELOCATION

Quoted 6 lines

CONFIG_RELOCATABLE on powerpc means something different. On arm we start U-Boot by running it at an address != link address and _copy_ (not relocate) ourselves to the address we are linked at. On powerpc real relocation is done if CONFIG_RELOCATABLE is enabled.
Hence the option you wanted to add should better have the name CONFIG_SKIP_COPY_TO_SDRAM or something like that.

Hmm.. good point. My ignorance on ppc is kicking me ;).. I will remove the SKIP_COPY part from my patch. Couple of questions:
a) Are we ok with removing dependency of ARM from "config SKIP_LOWLEVEL_INIT" in common/Kconfig (as opposed to my patch in which I moved it to arch/arm/Kconfig)? Considering that it is used: arch/m68k/cpu/start-mcfv4e.S

b) Further am wondering if it is fine to convert ARCH_HAS_INIT_LOWLEVEL to CONFIG_ARCH_HAS_INIT_LOWLEVEL in common/Kconfig and make it arch independent?

-----Original Message-----
From: Sascha Hauer [mailto:s.hauer at pengutronix.de]
Sent: Thursday, May 08, 2008 10:16 AM
To: Menon, Nishanth
Cc: u-boot-users at lists.sourceforge.net
Subject: Re: [Patch 2/4] U-Boot-V2: ARM: introduce CONFIG_SKIP_RELOCATION

Quoted 1 line

Hmm.. good point. My ignorance on ppc is kicking me ;).. I will remove the SKIP_COPY part from my

patch. Couple of questions:

Quoted 1 line

a) Are we ok with removing dependency of ARM from "config SKIP_LOWLEVEL_INIT" in common/Kconfig (as

opposed to my patch in which I moved it to arch/arm/Kconfig)? Considering that it is used:
arch/m68k/cpu/start-mcfv4e.S

so SKIP_LOWLEVEL_INIT would depend on CONFIG_ARCH_HAS_INIT_LOWLEVEL?

CONFIG_RELOCATABLE on powerpc means something different. On arm we start U-Boot by running it at an address != link address and _copy_ (not relocate) ourselves to the address we are linked at. On powerpc real relocation is done if CONFIG_RELOCATABLE is enabled.
Hence the option you wanted to add should better have the name CONFIG_SKIP_COPY_TO_SDRAM or something like that.

Quoted 6 lines

CONFIG_RELOCATABLE on powerpc means something different. On arm we start U-Boot by running it at an address != link address and _copy_ (not relocate) ourselves to the address we are linked at. On powerpc real relocation is done if CONFIG_RELOCATABLE is enabled.
Hence the option you wanted to add should better have the name CONFIG_SKIP_COPY_TO_SDRAM or something like that.

This is something that I always wanted to fix. The ARM implementation is broken by design - unfortunately it has been also used for MIPS, and other architectures. It would be much better if we had real relocation to a (dynamically determined) address on ARM too, instead of such a fixed mapping.

Best regards,

Wolfgang Denk

Quoted 7 lines · In message <[email protected]> you wrote:

CONFIG_RELOCATABLE on powerpc means something different. On arm we start U-Boot by running it at an address != link address and _copy_ (not relocate) ourselves to the address we are linked at. On powerpc real relocation is done if CONFIG_RELOCATABLE is enabled.
Hence the option you wanted to add should better have the name CONFIG_SKIP_COPY_TO_SDRAM or something like that.

This is something that I always wanted to fix. The ARM implementation is broken by design - unfortunately it has been also used for MIPS, and other architectures. It would be much better if we had real relocation to a (dynamically determined) address on ARM too, instead of such a fixed mapping.