linux-kernel - Re: [PATCH 8/9] [HACK] ARM: imx: work around v7_cpu

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Message-ID: <alpine.LFD.2.03.1302182245400.6419@syhkavp.arg>
Date:	Mon, 18 Feb 2013 23:11:30 -0500 (EST)
From:	Nicolas Pitre <nicolas.pitre@...aro.org>
To:	Shawn Guo <shawn.guo@...aro.org>
cc:	Russell King - ARM Linux <linux@....linux.org.uk>,
	Arnd Bergmann <arnd@...db.de>,
	linux-arm-kernel@...ts.infradead.org,
	Stephen Warren <swarren@...dia.com>,
	Pavel Machek <pavel@...x.de>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	linux-kernel@...r.kernel.org, arm@...nel.org,
	Simon Horman <horms+renesas@...ge.net.au>,
	Dinh Nguyen <dinguyen@...era.com>
Subject: Re: [PATCH 8/9] [HACK] ARM: imx: work around v7_cpu_resume link
 error

On Tue, 19 Feb 2013, Shawn Guo wrote:

> On Mon, Feb 18, 2013 at 12:06:32PM -0500, Nicolas Pitre wrote:
> > Try the following instead.  It makes the code simpler and easier to 
> > debug.
> > 
> It works now.  Thanks, Nico.  Care to send a patch for it?  I'd like
> to apply it.

----- >8

FRom: Nicolas Pitre <nicolas.pitre@...aro.org>
Date: Mon, 18 Feb 2013 12:06:32 -0500 (EST)
Subject: ARM: mach-imx: move early resume code out of the .data section

Building the kernel with allyesconfig fails because the i.mx early
resume code located in the .data section is unable to fixup the bl
relocation as the branch target gets too far away.

The idea of having code in the .data section allows for easy access to 
nearby data using relative addressing while the MMU is off. However it 
is probably best to move the code back to the .text section where it 
belongs and fixup the data access instead.  This solves the bl reloc
issue (at least until this becomes a general problem) and simplifies
the code as well.

Signed-off-by: Nicolas Pitre <nico@...aro.org>
---

I'll probably convert other "code in .data" instances as well in the 
near future.

diff --git a/arch/arm/mach-imx/headsmp.S b/arch/arm/mach-imx/headsmp.S
index 7e49deb128..27bc06e910 100644
--- a/arch/arm/mach-imx/headsmp.S
+++ b/arch/arm/mach-imx/headsmp.S
@@ -73,16 +73,16 @@ ENDPROC(v7_secondary_startup)
 
 #ifdef CONFIG_PM
 /*
- * The following code is located into the .data section.  This is to
- * allow phys_l2x0_saved_regs to be accessed with a relative load
- * as we are running on physical address here.
+ * The following code must assume it is running from physical address
+ * where absolute virtual addresses to the data section have to be
+ * turned into relative ones.
  */
-	.data
-	.align
 
 #ifdef CONFIG_CACHE_L2X0
 	.macro	pl310_resume
-	ldr	r2, phys_l2x0_saved_regs
+	adr	r0, l2x0_saved_regs_offset
+	ldr	r2, [r0]
+	add	r2, r2, r0
 	ldr	r0, [r2, #L2X0_R_PHY_BASE]	@ get physical base of l2x0
 	ldr	r1, [r2, #L2X0_R_AUX_CTRL]	@ get aux_ctrl value
 	str	r1, [r0, #L2X0_AUX_CTRL]	@ restore aux_ctrl
@@ -90,9 +90,9 @@ ENDPROC(v7_secondary_startup)
 	str	r1, [r0, #L2X0_CTRL]		@ re-enable L2
 	.endm
 
-	.globl	phys_l2x0_saved_regs
-phys_l2x0_saved_regs:
-        .long   0
+l2x0_saved_regs_offset:
+	.word	l2x0_saved_regs - .
+
 #else
 	.macro	pl310_resume
 	.endm
diff --git a/arch/arm/mach-imx/pm-imx6q.c b/arch/arm/mach-imx/pm-imx6q.c
index f7b0c2b1b9..f3791f980d 100644
--- a/arch/arm/mach-imx/pm-imx6q.c
+++ b/arch/arm/mach-imx/pm-imx6q.c
@@ -21,8 +21,6 @@
 #include <mach/common.h>
 #include <mach/hardware.h>
 
-extern unsigned long phys_l2x0_saved_regs;
-
 static int imx6q_suspend_finish(unsigned long val)
 {
 	cpu_do_idle();
@@ -55,18 +53,5 @@ static const struct platform_suspend_ops imx6q_pm_ops = {
 
 void __init imx6q_pm_init(void)
 {
-	/*
-	 * The l2x0 core code provides an infrastucture to save and restore
-	 * l2x0 registers across suspend/resume cycle.  But because imx6q
-	 * retains L2 content during suspend and needs to resume L2 before
-	 * MMU is enabled, it can only utilize register saving support and
-	 * have to take care of restoring on its own.  So we save physical
-	 * address of the data structure used by l2x0 core to save registers,
-	 * and later restore the necessary ones in imx6q resume entry.
-	 */
-#ifdef CONFIG_CACHE_L2X0
-	phys_l2x0_saved_regs = __pa(&l2x0_saved_regs);
-#endif
-
 	suspend_set_ops(&imx6q_pm_ops);
 }
--
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