[PATCH] power: reset: at91-reset: enable I-cache for at91sam9260_reset

[PATCH] power: reset: at91-reset: enable I-cache for at91sam9260_reset

[Jonas Danielsson]

From: Jonas Danielsson <jonas@orbital-systems.com>

This fixes a bug where our embedded system (AT91SAM9260 based) would
hang at reboot. At the most we managed 16 boot loops without a hang.

With this patch applied the problem has not been observed and the board
has managed above 250 boot loops.

The AT91SAM9260 datasheet tells us that with the instruction cache
disabled all instructions are fetched from SDRAM. And we have an errata
telling us we must power down the SDRAM before issuing cpu reset.

This means we need the instruction cache enabled in at91sam9260_reset()
At the moment it is being disabled in cpu_proc_fin() which is called from
arch/arm/kernel/reboot.c.

Signed-off-by: Jonas Danielsson <jonas@orbital-systems.com>
---
 drivers/power/reset/at91-reset.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/power/reset/at91-reset.c b/drivers/power/reset/at91-reset.c
index f44a9ffcc2ab..78972bba64df 100644
--- a/drivers/power/reset/at91-reset.c
+++ b/drivers/power/reset/at91-reset.c
@@ -50,14 +50,24 @@ static void __iomem *at91_ramc_base[2], *at91_rstc_base;
 static struct clk *sclk;
 
 /*
-* unless the SDRAM is cleanly shutdown before we hit the
+* Errata 43.1.7.1 RSTC: Reset during SDRAM Accesses
+*
+* Unless the SDRAM is cleanly shutdown before we hit the
 * reset register it can be left driving the data bus and
 * killing the chance of a subsequent boot from NAND
+*
+* Since we are disabling SDRAM need to make sure that the
+* instruction cache is enabled.
 */
 static int at91sam9260_restart(struct notifier_block *this, unsigned long mode,
 			       void *cmd)
 {
 	asm volatile(
+		/* Enable I-cache */
+		"mrc	p15, 0, r0, c1, c0, 0\n\t"
+		"orr	r0, r0, #4096\n\t" /* CR_I (bit 12) */
+		"mcr	p15, 0, r0, c1, c0, 0\n\t"
+
 		/* Align to cache lines */
 		".balign 32\n\t"
 
-- 
2.14.4

Re: [PATCH] power: reset: at91-reset: enable I-cache for at91sam9260_reset

[Claudiu.Beznea]

Hi Jonas,

On 07.10.2018 15:57, Jonas Danielsson wrote:
> From: Jonas Danielsson <jonas@orbital-systems.com>
> 
> This fixes a bug where our embedded system (AT91SAM9260 based) would
> hang at reboot. At the most we managed 16 boot loops without a hang.
> 
> With this patch applied the problem has not been observed and the board
> has managed above 250 boot loops.
> 
> The AT91SAM9260 datasheet tells us that with the instruction cache
> disabled all instructions are fetched from SDRAM. And we have an errata
> telling us we must power down the SDRAM before issuing cpu reset.
> 
> This means we need the instruction cache enabled in at91sam9260_reset()
> At the moment it is being disabled in cpu_proc_fin() which is called from
> arch/arm/kernel/reboot.c.

Are you using kexec reboot or implemented hibernate mode on this machine?
I'm seeing cpu_proc_fin() is called only in case of kexec reboot or
switching to hibernate mode.

In case of normal reboot (e.g. reboot command) machine_restart() from
arch/arm/kernel/reboot.c is called. Please correct me if I'm wrong.

Thank you,
Claudiu Beznea

> 
> Signed-off-by: Jonas Danielsson <jonas@orbital-systems.com>
> ---
>  drivers/power/reset/at91-reset.c | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/power/reset/at91-reset.c b/drivers/power/reset/at91-reset.c
> index f44a9ffcc2ab..78972bba64df 100644
> --- a/drivers/power/reset/at91-reset.c
> +++ b/drivers/power/reset/at91-reset.c
> @@ -50,14 +50,24 @@ static void __iomem *at91_ramc_base[2], *at91_rstc_base;
>  static struct clk *sclk;
>  
>  /*
> -* unless the SDRAM is cleanly shutdown before we hit the
> +* Errata 43.1.7.1 RSTC: Reset during SDRAM Accesses
> +*
> +* Unless the SDRAM is cleanly shutdown before we hit the
>  * reset register it can be left driving the data bus and
>  * killing the chance of a subsequent boot from NAND
> +*
> +* Since we are disabling SDRAM need to make sure that the
> +* instruction cache is enabled.
>  */
>  static int at91sam9260_restart(struct notifier_block *this, unsigned long mode,
>  			       void *cmd)
>  {
>  	asm volatile(
> +		/* Enable I-cache */
> +		"mrc	p15, 0, r0, c1, c0, 0\n\t"
> +		"orr	r0, r0, #4096\n\t" /* CR_I (bit 12) */
> +		"mcr	p15, 0, r0, c1, c0, 0\n\t"
> +
>  		/* Align to cache lines */
>  		".balign 32\n\t"
>  
> 

Re: [PATCH] power: reset: at91-reset: enable I-cache for at91sam9260_reset

[Alexander Stein]

Do you have CONFIG_CPU_ICACHE_DISABLE enabled?
I wonder why I-cache is disabled. I know about this errata, AT91SAM9G20 is affected as well.

Best regards,
Alexander

On Sunday, October 7, 2018, 2:57:45 PM CEST Jonas Danielsson wrote:
> From: Jonas Danielsson <jonas@orbital-systems.com>
> 
> This fixes a bug where our embedded system (AT91SAM9260 based) would
> hang at reboot. At the most we managed 16 boot loops without a hang.
> 
> With this patch applied the problem has not been observed and the board
> has managed above 250 boot loops.
> 
> The AT91SAM9260 datasheet tells us that with the instruction cache
> disabled all instructions are fetched from SDRAM. And we have an errata
> telling us we must power down the SDRAM before issuing cpu reset.
> 
> This means we need the instruction cache enabled in at91sam9260_reset()
> At the moment it is being disabled in cpu_proc_fin() which is called from
> arch/arm/kernel/reboot.c.
> 
> Signed-off-by: Jonas Danielsson <jonas@orbital-systems.com>
> ---
>  drivers/power/reset/at91-reset.c | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/power/reset/at91-reset.c b/drivers/power/reset/at91-reset.c
> index f44a9ffcc2ab..78972bba64df 100644
> --- a/drivers/power/reset/at91-reset.c
> +++ b/drivers/power/reset/at91-reset.c
> @@ -50,14 +50,24 @@ static void __iomem *at91_ramc_base[2], *at91_rstc_base;
>  static struct clk *sclk;
>  
>  /*
> -* unless the SDRAM is cleanly shutdown before we hit the
> +* Errata 43.1.7.1 RSTC: Reset during SDRAM Accesses
> +*
> +* Unless the SDRAM is cleanly shutdown before we hit the
>  * reset register it can be left driving the data bus and
>  * killing the chance of a subsequent boot from NAND
> +*
> +* Since we are disabling SDRAM need to make sure that the
> +* instruction cache is enabled.
>  */
>  static int at91sam9260_restart(struct notifier_block *this, unsigned long mode,
>  			       void *cmd)
>  {
>  	asm volatile(
> +		/* Enable I-cache */
> +		"mrc	p15, 0, r0, c1, c0, 0\n\t"
> +		"orr	r0, r0, #4096\n\t" /* CR_I (bit 12) */
> +		"mcr	p15, 0, r0, c1, c0, 0\n\t"
> +
>  		/* Align to cache lines */
>  		".balign 32\n\t"
>  
> 


-- 
SYS TEC electronic GmbH
Am Windrad 2
08468 Heinsdorfergrund
Germany
Telefon : +49 (0) 3765 38600-0
Fax     : +49 (0) 3765 38600-4100
Email   : alexander.stein@systec-electronic.com
Website : http://www.systec-electronic.com

Managing Director   : Dipl.-Phys. Siegmar Schmidt
Commercial registry : Amtsgericht Chemnitz, HRB 28082
USt.-Id Nr.         : DE150534010

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Re: [PATCH] power: reset: at91-reset: enable I-cache for at91sam9260_reset

[Jonas Danielsson]

On Tue, Oct 16, 2018 at 3:30 PM <Claudiu.Beznea@microchip.com> wrote:
>
> Hi Jonas,
>

Hi,

> On 07.10.2018 15:57, Jonas Danielsson wrote:
> > From: Jonas Danielsson <jonas@orbital-systems.com>
> >
> > This fixes a bug where our embedded system (AT91SAM9260 based) would
> > hang at reboot. At the most we managed 16 boot loops without a hang.
> >
> > With this patch applied the problem has not been observed and the board
> > has managed above 250 boot loops.
> >
> > The AT91SAM9260 datasheet tells us that with the instruction cache
> > disabled all instructions are fetched from SDRAM. And we have an errata
> > telling us we must power down the SDRAM before issuing cpu reset.
> >
> > This means we need the instruction cache enabled in at91sam9260_reset()
> > At the moment it is being disabled in cpu_proc_fin() which is called from
> > arch/arm/kernel/reboot.c.
>
> Are you using kexec reboot or implemented hibernate mode on this machine?
> I'm seeing cpu_proc_fin() is called only in case of kexec reboot or
> switching to hibernate mode.
>
> In case of normal reboot (e.g. reboot command) machine_restart() from
> arch/arm/kernel/reboot.c is called. Please correct me if I'm wrong.
>

We are not, we do regular reboots. I have read the code paths wrong.
Then I wonder what disables icache.

> Thank you,
> Claudiu Beznea

Thank you!

>
> >
> > Signed-off-by: Jonas Danielsson <jonas@orbital-systems.com>
> > ---
> >  drivers/power/reset/at91-reset.c | 12 +++++++++++-
> >  1 file changed, 11 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/power/reset/at91-reset.c b/drivers/power/reset/at91-reset.c
> > index f44a9ffcc2ab..78972bba64df 100644
> > --- a/drivers/power/reset/at91-reset.c
> > +++ b/drivers/power/reset/at91-reset.c
> > @@ -50,14 +50,24 @@ static void __iomem *at91_ramc_base[2], *at91_rstc_base;
> >  static struct clk *sclk;
> >
> >  /*
> > -* unless the SDRAM is cleanly shutdown before we hit the
> > +* Errata 43.1.7.1 RSTC: Reset during SDRAM Accesses
> > +*
> > +* Unless the SDRAM is cleanly shutdown before we hit the
> >  * reset register it can be left driving the data bus and
> >  * killing the chance of a subsequent boot from NAND
> > +*
> > +* Since we are disabling SDRAM need to make sure that the
> > +* instruction cache is enabled.
> >  */
> >  static int at91sam9260_restart(struct notifier_block *this, unsigned long mode,
> >                              void *cmd)
> >  {
> >       asm volatile(
> > +             /* Enable I-cache */
> > +             "mrc    p15, 0, r0, c1, c0, 0\n\t"
> > +             "orr    r0, r0, #4096\n\t" /* CR_I (bit 12) */
> > +             "mcr    p15, 0, r0, c1, c0, 0\n\t"
> > +
> >               /* Align to cache lines */
> >               ".balign 32\n\t"
> >
> >



-- 






JONAS DANIELSSON
Software Developer

+46 72 361 5022
Malmö - Sweden

ORBITAL SYSTEMS
orbital-systems.com




The information contained in this message is intended for the personal
and confidential use of the designated recipients named above and may
contain confidential and/or privileged material. If the reader of this
message is not the intended recipient or an agent responsible for
delivering it to the intended recipient, you are hereby notified that
you have received this document in error, and that any review,
dissemination, distribution, or copying of this message is strictly
prohibited. If you have received this communication in error, please
notify the sender immediately and delete this e-mail from your system.

Although this transmission and any attachments are believed to be free
of any virus or other defect that might affect any computer system
into which it is received and opened, it is the responsibility of the
recipient to ensure that it is virus free and no responsibility is
accepted by ORBITAL SYSTEMS AB, its subsidiaries and affiliates, as
applicable, for any loss or damage arising in any way.

Re: [PATCH] power: reset: at91-reset: enable I-cache for at91sam9260_reset

[Jonas Danielsson]

On Tue, Oct 16, 2018 at 4:03 PM Alexander Stein
<alexander.stein@systec-electronic.com> wrote:
>
> Do you have CONFIG_CPU_ICACHE_DISABLE enabled?
> I wonder why I-cache is disabled. I know about this errata, AT91SAM9G20 is affected as well.
>

Hi Alexander!

I just checked, we do not have CONFIG_CPU_ICACHE_DISABLE enabled.
I wonder as well! If you have any idea I can try them out on my board tomorrow!

The effect of enabling them is real. I have managed over 1000 reboots
with this patch.
And at the most 20 without.

> Best regards,
> Alexander

Jonas

>
> On Sunday, October 7, 2018, 2:57:45 PM CEST Jonas Danielsson wrote:
> > From: Jonas Danielsson <jonas@orbital-systems.com>
> >
> > This fixes a bug where our embedded system (AT91SAM9260 based) would
> > hang at reboot. At the most we managed 16 boot loops without a hang.
> >
> > With this patch applied the problem has not been observed and the board
> > has managed above 250 boot loops.
> >
> > The AT91SAM9260 datasheet tells us that with the instruction cache
> > disabled all instructions are fetched from SDRAM. And we have an errata
> > telling us we must power down the SDRAM before issuing cpu reset.
> >
> > This means we need the instruction cache enabled in at91sam9260_reset()
> > At the moment it is being disabled in cpu_proc_fin() which is called from
> > arch/arm/kernel/reboot.c.
> >
> > Signed-off-by: Jonas Danielsson <jonas@orbital-systems.com>
> > ---
> >  drivers/power/reset/at91-reset.c | 12 +++++++++++-
> >  1 file changed, 11 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/power/reset/at91-reset.c b/drivers/power/reset/at91-reset.c
> > index f44a9ffcc2ab..78972bba64df 100644
> > --- a/drivers/power/reset/at91-reset.c
> > +++ b/drivers/power/reset/at91-reset.c
> > @@ -50,14 +50,24 @@ static void __iomem *at91_ramc_base[2], *at91_rstc_base;
> >  static struct clk *sclk;
> >
> >  /*
> > -* unless the SDRAM is cleanly shutdown before we hit the
> > +* Errata 43.1.7.1 RSTC: Reset during SDRAM Accesses
> > +*
> > +* Unless the SDRAM is cleanly shutdown before we hit the
> >  * reset register it can be left driving the data bus and
> >  * killing the chance of a subsequent boot from NAND
> > +*
> > +* Since we are disabling SDRAM need to make sure that the
> > +* instruction cache is enabled.
> >  */
> >  static int at91sam9260_restart(struct notifier_block *this, unsigned long mode,
> >                              void *cmd)
> >  {
> >       asm volatile(
> > +             /* Enable I-cache */
> > +             "mrc    p15, 0, r0, c1, c0, 0\n\t"
> > +             "orr    r0, r0, #4096\n\t" /* CR_I (bit 12) */
> > +             "mcr    p15, 0, r0, c1, c0, 0\n\t"
> > +
> >               /* Align to cache lines */
> >               ".balign 32\n\t"
> >
> >
>
>
> --
> SYS TEC electronic GmbH
> Am Windrad 2
> 08468 Heinsdorfergrund
> Germany
> Telefon : +49 (0) 3765 38600-0
> Fax     : +49 (0) 3765 38600-4100
> Email   : alexander.stein@systec-electronic.com
> Website : http://www.systec-electronic.com
>
> Managing Director   : Dipl.-Phys. Siegmar Schmidt
> Commercial registry : Amtsgericht Chemnitz, HRB 28082
> USt.-Id Nr.         : DE150534010
>
> Diese E-Mail enthält vertrauliche und/oder rechtlich geschützte Informationen.
> Wenn Sie nicht der richtige Adressat sind oder diese E-Mail irrtümlich erhalten haben, informieren Sie bitte sofort den Absender und vernichten Sie diese Mail.
> Das unerlaubte Kopieren sowie die unbefugte Weitergabe dieser Mail sind nicht gestattet.
>
> This e-mail may contain confidential and/or privileged information.
> If you are not the intended recipient (or have received this e-mail in error) please notify the sender immediately and destroy this e-mail.
> Any unauthorized copying, disclosure or distribution of the material in this e-mail is strictly forbidden.
>
>


-- 






JONAS DANIELSSON
Software Developer

+46 72 361 5022
Malmö - Sweden

ORBITAL SYSTEMS
orbital-systems.com




The information contained in this message is intended for the personal
and confidential use of the designated recipients named above and may
contain confidential and/or privileged material. If the reader of this
message is not the intended recipient or an agent responsible for
delivering it to the intended recipient, you are hereby notified that
you have received this document in error, and that any review,
dissemination, distribution, or copying of this message is strictly
prohibited. If you have received this communication in error, please
notify the sender immediately and delete this e-mail from your system.

Although this transmission and any attachments are believed to be free
of any virus or other defect that might affect any computer system
into which it is received and opened, it is the responsibility of the
recipient to ensure that it is virus free and no responsibility is
accepted by ORBITAL SYSTEMS AB, its subsidiaries and affiliates, as
applicable, for any loss or damage arising in any way.

Re: [PATCH] power: reset: at91-reset: enable I-cache for at91sam9260_reset

[Alexander Stein]

On Tuesday, October 16, 2018, 3:30:24 PM CEST Claudiu.Beznea@microchip.com wrote:
> Hi Jonas,
> 
> On 07.10.2018 15:57, Jonas Danielsson wrote:
> > From: Jonas Danielsson <jonas@orbital-systems.com>
> > 
> > This fixes a bug where our embedded system (AT91SAM9260 based) would
> > hang at reboot. At the most we managed 16 boot loops without a hang.
> > 
> > With this patch applied the problem has not been observed and the board
> > has managed above 250 boot loops.
> > 
> > The AT91SAM9260 datasheet tells us that with the instruction cache
> > disabled all instructions are fetched from SDRAM. And we have an errata
> > telling us we must power down the SDRAM before issuing cpu reset.
> > 
> > This means we need the instruction cache enabled in at91sam9260_reset()
> > At the moment it is being disabled in cpu_proc_fin() which is called from
> > arch/arm/kernel/reboot.c.
> 
> Are you using kexec reboot or implemented hibernate mode on this machine?
> I'm seeing cpu_proc_fin() is called only in case of kexec reboot or
> switching to hibernate mode.
> 
> In case of normal reboot (e.g. reboot command) machine_restart() from
> arch/arm/kernel/reboot.c is called. Please correct me if I'm wrong.

Another location is cpu_reset() aka cpu_arm926_reset() in proc-arm926.S
which also disables I-cache. But I can't track down a callstack
ending there.

Best regards,
Alexander

Re: [PATCH] power: reset: at91-reset: enable I-cache for at91sam9260_reset

[Jonas Danielsson]

On Tue, Oct 16, 2018 at 4:52 PM Alexander Stein
<alexander.stein@systec-electronic.com> wrote:
>
> On Tuesday, October 16, 2018, 3:30:24 PM CEST Claudiu.Beznea@microchip.com wrote:
> > Hi Jonas,
> >
> > On 07.10.2018 15:57, Jonas Danielsson wrote:
> > > From: Jonas Danielsson <jonas@orbital-systems.com>
> > >
> > > This fixes a bug where our embedded system (AT91SAM9260 based) would
> > > hang at reboot. At the most we managed 16 boot loops without a hang.
> > >
> > > With this patch applied the problem has not been observed and the board
> > > has managed above 250 boot loops.
> > >
> > > The AT91SAM9260 datasheet tells us that with the instruction cache
> > > disabled all instructions are fetched from SDRAM. And we have an errata
> > > telling us we must power down the SDRAM before issuing cpu reset.
> > >
> > > This means we need the instruction cache enabled in at91sam9260_reset()
> > > At the moment it is being disabled in cpu_proc_fin() which is called from
> > > arch/arm/kernel/reboot.c.
> >
> > Are you using kexec reboot or implemented hibernate mode on this machine?
> > I'm seeing cpu_proc_fin() is called only in case of kexec reboot or
> > switching to hibernate mode.
> >
> > In case of normal reboot (e.g. reboot command) machine_restart() from
> > arch/arm/kernel/reboot.c is called. Please correct me if I'm wrong.
>
> Another location is cpu_reset() aka cpu_arm926_reset() in proc-arm926.S
> which also disables I-cache. But I can't track down a callstack
> ending there.
>

We take the normal path of sys_reboot => kernel_restart => machine_restart ...

I added code to print the c1 register in different paths. And I-cache
is enabled.
So now I am really confused about why the patch worked.

> Best regards,
> Alexander

Jonas

>
>
>


-- 






JONAS DANIELSSON
Software Developer

+46 72 361 5022
Malmö - Sweden

ORBITAL SYSTEMS
orbital-systems.com




The information contained in this message is intended for the personal
and confidential use of the designated recipients named above and may
contain confidential and/or privileged material. If the reader of this
message is not the intended recipient or an agent responsible for
delivering it to the intended recipient, you are hereby notified that
you have received this document in error, and that any review,
dissemination, distribution, or copying of this message is strictly
prohibited. If you have received this communication in error, please
notify the sender immediately and delete this e-mail from your system.

Although this transmission and any attachments are believed to be free
of any virus or other defect that might affect any computer system
into which it is received and opened, it is the responsibility of the
recipient to ensure that it is virus free and no responsibility is
accepted by ORBITAL SYSTEMS AB, its subsidiaries and affiliates, as
applicable, for any loss or damage arising in any way.

Re: [PATCH] power: reset: at91-reset: enable I-cache for at91sam9260_reset

[Claudiu.Beznea]

On 17.10.2018 15:17, Jonas Danielsson wrote:
> On Tue, Oct 16, 2018 at 4:52 PM Alexander Stein
> <alexander.stein@systec-electronic.com> wrote:
>>
>> On Tuesday, October 16, 2018, 3:30:24 PM CEST Claudiu.Beznea@microchip.com wrote:
>>> Hi Jonas,
>>>
>>> On 07.10.2018 15:57, Jonas Danielsson wrote:
>>>> From: Jonas Danielsson <jonas@orbital-systems.com>
>>>>
>>>> This fixes a bug where our embedded system (AT91SAM9260 based) would
>>>> hang at reboot. At the most we managed 16 boot loops without a hang.
>>>>
>>>> With this patch applied the problem has not been observed and the board
>>>> has managed above 250 boot loops.
>>>>
>>>> The AT91SAM9260 datasheet tells us that with the instruction cache
>>>> disabled all instructions are fetched from SDRAM. And we have an errata
>>>> telling us we must power down the SDRAM before issuing cpu reset.
>>>>
>>>> This means we need the instruction cache enabled in at91sam9260_reset()
>>>> At the moment it is being disabled in cpu_proc_fin() which is called from
>>>> arch/arm/kernel/reboot.c.
>>>
>>> Are you using kexec reboot or implemented hibernate mode on this machine?
>>> I'm seeing cpu_proc_fin() is called only in case of kexec reboot or
>>> switching to hibernate mode.
>>>
>>> In case of normal reboot (e.g. reboot command) machine_restart() from
>>> arch/arm/kernel/reboot.c is called. Please correct me if I'm wrong.
>>
>> Another location is cpu_reset() aka cpu_arm926_reset() in proc-arm926.S
>> which also disables I-cache. But I can't track down a callstack
>> ending there.
>>
> 
> We take the normal path of sys_reboot => kernel_restart => machine_restart ...
> 
> I added code to print the c1 register in different paths. And I-cache
> is enabled.
> So now I am really confused about why the patch worked.

Just saying... maybe your instructions add some delay on the execution path
and this is why it helps... try to access cp15 co-processor for read and
write back the value you read without actually to modify it, to see if this
could be the reason: e.g.:

mrc	p15, 0, r0, c1, c0, 0
orr	r1, r1, #4096		// whatever is in r1, doesn't matter
mcr	p15, 0, r0, c1, c0, 0

Thank you,
Claudiu Beznea

> 
>> Best regards,
>> Alexander
> 
> Jonas
> 
>>
>>
>>
> 
> 

Re: [PATCH] power: reset: at91-reset: enable I-cache for at91sam9260_reset

[Jonas Danielsson]

On Wed, Oct 17, 2018 at 3:10 PM <Claudiu.Beznea@microchip.com> wrote:
>
> >
> > We take the normal path of sys_reboot => kernel_restart => machine_restart ...
> >
> > I added code to print the c1 register in different paths. And I-cache
> > is enabled.
> > So now I am really confused about why the patch worked.
>
> Just saying... maybe your instructions add some delay on the execution path
> and this is why it helps... try to access cp15 co-processor for read and
> write back the value you read without actually to modify it, to see if this
> could be the reason: e.g.:
>
> mrc     p15, 0, r0, c1, c0, 0
> orr     r1, r1, #4096           // whatever is in r1, doesn't matter
> mcr     p15, 0, r0, c1, c0, 0
>

Yes, this also seems to work. I have over 100 reboots completed with this code.
So what could be the issue here? It seem related to the powering down
of the sdram at least.

This thread on the AT91SAM community deals with the same issue:
http://www.at91.com/viewtopic.php?t=25830
There the solution people chose was removing the SDRAM powering down.
But that leaves one open to the cause of the errata.

Do you have any thought on how to approach this?

> Thank you,
> Claudiu Beznea
>

Regards
Jonas


> >
> >> Best regards,
> >> Alexander
> >
> > Jonas
> >
> >>
> >>
> >>
> >
> >



-- 






JONAS DANIELSSON
Software Developer

+46 72 361 5022
Malmö - Sweden

ORBITAL SYSTEMS
orbital-systems.com




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Re: [PATCH] power: reset: at91-reset: enable I-cache for at91sam9260_reset

[Claudiu.Beznea]

On 19.10.2018 13:30, Jonas Danielsson wrote:
> On Wed, Oct 17, 2018 at 3:10 PM <Claudiu.Beznea@microchip.com> wrote:
>>
>>>
>>> We take the normal path of sys_reboot => kernel_restart => machine_restart ...
>>>
>>> I added code to print the c1 register in different paths. And I-cache
>>> is enabled.
>>> So now I am really confused about why the patch worked.
>>
>> Just saying... maybe your instructions add some delay on the execution path
>> and this is why it helps... try to access cp15 co-processor for read and
>> write back the value you read without actually to modify it, to see if this
>> could be the reason: e.g.:
>>
>> mrc     p15, 0, r0, c1, c0, 0
>> orr     r1, r1, #4096           // whatever is in r1, doesn't matter
>> mcr     p15, 0, r0, c1, c0, 0
>>
> 
> Yes, this also seems to work. I have over 100 reboots completed with this code.
> So what could be the issue here? It seem related to the powering down
> of the sdram at least.

I don't know what could be the issue here. 

> 
> This thread on the AT91SAM community deals with the same issue:
> http://www.at91.com/viewtopic.php?t=25830
> There the solution people chose was removing the SDRAM powering down.
> But that leaves one open to the cause of the errata.
> 
> Do you have any thought on how to approach this?

For now, no. I didn't dug this issue.

Thank you,
Claudiu

> 
>> Thank you,
>> Claudiu Beznea
>>
> 
> Regards
> Jonas
> 
> 
>>>
>>>> Best regards,
>>>> Alexander
>>>
>>> Jonas
>>>
>>>>
>>>>
>>>>
>>>
>>>
> 
> 
>