[PATCH] ARM: save/restore diagnostic register on ARMv7 suspend/resume

[PATCH] ARM: save/restore diagnostic register on ARMv7 suspend/resume

[Shawn Guo]

The CP15 diagnostic register holds ARM errata bits on ARMv7, so it
needs to be saved/restored on suspend/resume.  Otherwise, the
effectiveness of errata workaround gets lost together with diagnostic
register bit across suspend/resume cycle.

Signed-off-by: Shawn Guo <shawn.guo@freescale.com>
---
 arch/arm/mm/proc-v7.S | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
index 3db2c2f04a30..4de98a65a4ea 100644
--- a/arch/arm/mm/proc-v7.S
+++ b/arch/arm/mm/proc-v7.S
@@ -92,13 +92,14 @@ ENDPROC(cpu_v7_dcache_clean_area)
 
 /* Suspend/resume support: derived from arch/arm/mach-s5pv210/sleep.S */
 .globl	cpu_v7_suspend_size
-.equ	cpu_v7_suspend_size, 4 * 9
+.equ	cpu_v7_suspend_size, 4 * 10
 #ifdef CONFIG_ARM_CPU_SUSPEND
 ENTRY(cpu_v7_do_suspend)
 	stmfd	sp!, {r4 - r10, lr}
 	mrc	p15, 0, r4, c13, c0, 0	@ FCSE/PID
 	mrc	p15, 0, r5, c13, c0, 3	@ User r/o thread ID
 	stmia	r0!, {r4 - r5}
+	mrc	p15, 0, r4, c15, c0, 1	@ Diagnostic register
 #ifdef CONFIG_MMU
 	mrc	p15, 0, r6, c3, c0, 0	@ Domain ID
 #ifdef CONFIG_ARM_LPAE
@@ -111,7 +112,7 @@ ENTRY(cpu_v7_do_suspend)
 	mrc	p15, 0, r8, c1, c0, 0	@ Control register
 	mrc	p15, 0, r9, c1, c0, 1	@ Auxiliary control register
 	mrc	p15, 0, r10, c1, c0, 2	@ Co-processor access control
-	stmia	r0, {r5 - r11}
+	stmia	r0, {r4 - r11}
 	ldmfd	sp!, {r4 - r10, pc}
 ENDPROC(cpu_v7_do_suspend)
 
@@ -122,7 +123,8 @@ ENTRY(cpu_v7_do_resume)
 	ldmia	r0!, {r4 - r5}
 	mcr	p15, 0, r4, c13, c0, 0	@ FCSE/PID
 	mcr	p15, 0, r5, c13, c0, 3	@ User r/o thread ID
-	ldmia	r0, {r5 - r11}
+	ldmia	r0, {r4 - r11}
+	mcr	p15, 0, r4, c15, c0, 1	@ Diagnostic register
 #ifdef CONFIG_MMU
 	mcr	p15, 0, ip, c8, c7, 0	@ invalidate TLBs
 	mcr	p15, 0, r6, c3, c0, 0	@ Domain ID
-- 
1.8.3.2

[PATCH] ARM: save/restore diagnostic register on ARMv7 suspend/resume

[Will Deacon]

On Wed, Jun 18, 2014 at 09:49:58AM +0100, Shawn Guo wrote:
> The CP15 diagnostic register holds ARM errata bits on ARMv7, so it
> needs to be saved/restored on suspend/resume.  Otherwise, the
> effectiveness of errata workaround gets lost together with diagnostic
> register bit across suspend/resume cycle.

This should be conditional on Cortex-A9, since this register is certainly
not architected.

Will

[PATCH] ARM: save/restore diagnostic register on ARMv7 suspend/resume

[Shawn Guo]

On Wed, Jun 18, 2014 at 11:40:09AM +0100, Will Deacon wrote:
> On Wed, Jun 18, 2014 at 09:49:58AM +0100, Shawn Guo wrote:
> > The CP15 diagnostic register holds ARM errata bits on ARMv7, so it
> > needs to be saved/restored on suspend/resume.  Otherwise, the
> > effectiveness of errata workaround gets lost together with diagnostic
> > register bit across suspend/resume cycle.
> 
> This should be conditional on Cortex-A9, since this register is certainly
> not architected.

Ah, yes.  In that case, I should probably handle it at platform level to
avoid messing up generic ARMv7 suspend/resume routines.

Shawn

[PATCH] ARM: save/restore diagnostic register on ARMv7 suspend/resume

[Russell King - ARM Linux]

On Wed, Jun 18, 2014 at 08:39:08PM +0800, Shawn Guo wrote:
> On Wed, Jun 18, 2014 at 11:40:09AM +0100, Will Deacon wrote:
> > On Wed, Jun 18, 2014 at 09:49:58AM +0100, Shawn Guo wrote:
> > > The CP15 diagnostic register holds ARM errata bits on ARMv7, so it
> > > needs to be saved/restored on suspend/resume.  Otherwise, the
> > > effectiveness of errata workaround gets lost together with diagnostic
> > > register bit across suspend/resume cycle.
> > 
> > This should be conditional on Cortex-A9, since this register is certainly
> > not architected.
> 
> Ah, yes.  In that case, I should probably handle it at platform level to
> avoid messing up generic ARMv7 suspend/resume routines.

We don't need more platform code repeating this kind of stuff...

All Cortex-A9 which have these work-arounds enabled may need this and
as the generic kernel already fiddles with this, it's something that
should not be platform specific - indeed, some of these workarounds
are supposed to be in place before the MMU is enabled.

So, it's being done at the preferred place in the kernel... just not
in a way that results in only Cortex A9 being affected.

-- 
FTTC broadband for 0.8mile line: now at 9.7Mbps down 460kbps up... slowly
improving, and getting towards what was expected from it.

[PATCH] ARM: save/restore diagnostic register on ARMv7 suspend/resume

[Nicolas Pitre]

On Wed, 18 Jun 2014, Shawn Guo wrote:

> On Wed, Jun 18, 2014 at 11:40:09AM +0100, Will Deacon wrote:
> > On Wed, Jun 18, 2014 at 09:49:58AM +0100, Shawn Guo wrote:
> > > The CP15 diagnostic register holds ARM errata bits on ARMv7, so it
> > > needs to be saved/restored on suspend/resume.  Otherwise, the
> > > effectiveness of errata workaround gets lost together with diagnostic
> > > register bit across suspend/resume cycle.
> > 
> > This should be conditional on Cortex-A9, since this register is certainly
> > not architected.
> 
> Ah, yes.  In that case, I should probably handle it at platform level to
> avoid messing up generic ARMv7 suspend/resume routines.

Please don't do that.

You may look at commit 16c79a3776 and do something similar for 
Cortex-A9.


Nicolas

[PATCH] ARM: save/restore diagnostic register on ARMv7 suspend/resume

[Shawn Guo]

On Wed, Jun 18, 2014 at 10:37:15AM -0400, Nicolas Pitre wrote:
> On Wed, 18 Jun 2014, Shawn Guo wrote:
> 
> > On Wed, Jun 18, 2014 at 11:40:09AM +0100, Will Deacon wrote:
> > > On Wed, Jun 18, 2014 at 09:49:58AM +0100, Shawn Guo wrote:
> > > > The CP15 diagnostic register holds ARM errata bits on ARMv7, so it
> > > > needs to be saved/restored on suspend/resume.  Otherwise, the
> > > > effectiveness of errata workaround gets lost together with diagnostic
> > > > register bit across suspend/resume cycle.
> > > 
> > > This should be conditional on Cortex-A9, since this register is certainly
> > > not architected.
> > 
> > Ah, yes.  In that case, I should probably handle it at platform level to
> > avoid messing up generic ARMv7 suspend/resume routines.
> 
> Please don't do that.
> 
> You may look at commit 16c79a3776 and do something similar for 
> Cortex-A9.

Okay.  Thanks for the hint, Nico.  Will work out a V2 patch soon.

Shawn