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Boot hang on Origen with (!SMP && CPU_IDLE)

Message ID CAHbNUh18WkH4CFcaeP1Tdjm3L-Rr0xVzgCnAHoPbbCFRWjKyxg@mail.gmail.com (mailing list archive)
State New, archived
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Commit Message

Tushar Behera Jan. 6, 2014, 10:31 a.m. UTC
On 3 January 2014 19:28, Tomasz Figa <t.figa@samsung.com> wrote:
> On Friday 03 of January 2014 14:37:10 Arnd Bergmann wrote:
>> On Friday 03 January 2014, Tushar Behera wrote:

[ ... ]

>> Hmm, the boot log contains no message about the l2 cache controller getting
>> initialized, which means that l2x0_of_init probably failed before calling
>> l2x0_init. It also seems that the dts files distributed with the kernel
>> are lacking nodes for the l2x0 device, which is indeed a perfectly good
>> explanation although it doesn't explain at all why it ever worked on
>> any system with my patch.
>>
>> Can you check if there is a correct cache controller node in your device
>> tree, and whether it works when you add one? If so, we should probably
>> add a couple of stable backport patches to the dts files. It would also

The device tree node for l2x0 device was missing. After adding a node
as below I can start booting Origen board.


>
> Tushar, do you maybe also have CONFIG_CACHE_L2X0 enabled?
>

Yes, this config option is enabled. If this is disabled, I don't see
this problem.

> Generally I can see two different issues here:
>
> 1) Broken handling of L2 cache in plat-samsung/sleep.S. It assumes that
> whenever CONFIG_CACHE_L2X0 is enabled, L2 cache is enabled too.
>
> This needs to go away. On normal resume from sleep, there is no need to
> do anything with L2X0 at such early stage. This reinitialization can be
> safely done later, by calling generic outer_resume().
>
> The problem shows up when you look at AFTR and LPA idle modes. They keep
> L2 cache contents, but L2X0 registers must be restored to let the cache
> operate normally. This must happen early enough to keep cache data
> consistent. Still, the code doing this must consider whether the cache
> was enabled before entering AFTR/LPA and whether secure firmware is used
> (see below), so this is a bit tricky.
>
> 2) There is no L2 cache controller node in Exynos4*.dtsi.
>
> It should be added, but L2 cache can't be enabled on all boards yet,
> since on boards where secure firmware is enabled, special configuration
> involving SMC calls is required. Patches for this are queued on my work
> queue, but it's quite tricky due to 1), which needs to consider whether
> secure firmware is enabled or not.
>

In that case, would it be ok to add the node for Origen board only?

Comments

Arnd Bergmann Jan. 6, 2014, 3:30 p.m. UTC | #1
On Monday 06 January 2014, Tushar Behera wrote:
> The device tree node for l2x0 device was missing. After adding a node
> as below I can start booting Origen board.
> 
> diff --git a/arch/arm/boot/dts/exynos4210-origen.dts
> b/arch/arm/boot/dts/exynos4210-origen.dts
> index 1a12fb2..675f323 100644
> --- a/arch/arm/boot/dts/exynos4210-origen.dts
> +++ b/arch/arm/boot/dts/exynos4210-origen.dts
> @@ -32,6 +32,13 @@
> 
> +       l2-cache-controller@10502000 {
> +               compatible = "arm,pl310-cache";
> +               reg = <0x10502000 0x1000>;
> +               cache-unified;
> +               cache-level = <2>;
> +       };
> +

Ok, very good!

> >> be a good time to get rid of the L2_AUX_VAL and L2_AUX_MASK defines and
> >> just read the respective settings from DT.
> 
> Ok.

Does the node you list above have the right settings for this?

> > 2) There is no L2 cache controller node in Exynos4*.dtsi.
> >
> > It should be added, but L2 cache can't be enabled on all boards yet,
> > since on boards where secure firmware is enabled, special configuration
> > involving SMC calls is required. Patches for this are queued on my work
> > queue, but it's quite tricky due to 1), which needs to consider whether
> > secure firmware is enabled or not.
> >
> 
> In that case, would it be ok to add the node for Origen board only?

Wouldn't that leave other systems still broken? I'm particularly worried
about what patch to backport to linux-stable. We should definitely add
the node for Origen, but we may also have to revert my broken patch
in all affected kernel versions.

Are there any systems that may or may not have secure firmware enabled
depending on the boot loader, or do we always know whether secure firmware
is there or not?

	Arnd
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Tomasz Figa Jan. 6, 2014, 4:41 p.m. UTC | #2
On Monday 06 of January 2014 16:30:56 Arnd Bergmann wrote:
> On Monday 06 January 2014, Tushar Behera wrote:
> > The device tree node for l2x0 device was missing. After adding a node
> > as below I can start booting Origen board.
> > 
> > diff --git a/arch/arm/boot/dts/exynos4210-origen.dts
> > b/arch/arm/boot/dts/exynos4210-origen.dts
> > index 1a12fb2..675f323 100644
> > --- a/arch/arm/boot/dts/exynos4210-origen.dts
> > +++ b/arch/arm/boot/dts/exynos4210-origen.dts
> > @@ -32,6 +32,13 @@
> > 
> > +       l2-cache-controller@10502000 {
> > +               compatible = "arm,pl310-cache";
> > +               reg = <0x10502000 0x1000>;
> > +               cache-unified;
> > +               cache-level = <2>;
> > +       };
> > +
> 
> Ok, very good!
> 
> > >> be a good time to get rid of the L2_AUX_VAL and L2_AUX_MASK defines and
> > >> just read the respective settings from DT.
> > 
> > Ok.
> 
> Does the node you list above have the right settings for this?
> 
> > > 2) There is no L2 cache controller node in Exynos4*.dtsi.
> > >
> > > It should be added, but L2 cache can't be enabled on all boards yet,
> > > since on boards where secure firmware is enabled, special configuration
> > > involving SMC calls is required. Patches for this are queued on my work
> > > queue, but it's quite tricky due to 1), which needs to consider whether
> > > secure firmware is enabled or not.
> > >
> > 
> > In that case, would it be ok to add the node for Origen board only?

Better solution would be to add the node in SoC-level dtsi, keep it
disabled and override the status to okay at board level. Still...

> 
> Wouldn't that leave other systems still broken? I'm particularly worried
> about what patch to backport to linux-stable. We should definitely add
> the node for Origen, but we may also have to revert my broken patch
> in all affected kernel versions.

...Origen is not the only board that is affected by this, most likely any
Exynos4-based board not running under secure firmware is.

> 
> Are there any systems that may or may not have secure firmware enabled
> depending on the boot loader, or do we always know whether secure firmware
> is there or not?

It always depends on the boot loader, but fortunately it's unlikely to
happen that one board will have both secure-enabled and normal bootloaders
available and in use, at least for Exynos4-based boards, so it's quite
safe to assume presence of secure firmware on per board basis and so you
have the secure firmware device tree node only in dts files of boards
that are known to use secure firmware.

Aynway, from what I can see, support for the only two Exynos4 boards using
for secure firmware was added in 3.12. This means that we can revert the
offending patch for 3.11, but for 3.12 and newer we can't, because this
will break such boards with CONFIG_L2X0 enabled.

Instead, wouldn't it be better to fix the issue at its cause? This means
s5p-sleep.S re-enabling L2X0 only if it was really enabled before entering
low power mode. This could be achieved by checking if l2x0_regs_phys isn't
0 for example (which isn't a valid physical RAM address on Exynos).

What do you think?

Best regards,
Tomasz

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diff mbox

Patch

diff --git a/arch/arm/boot/dts/exynos4210-origen.dts
b/arch/arm/boot/dts/exynos4210-origen.dts
index 1a12fb2..675f323 100644
--- a/arch/arm/boot/dts/exynos4210-origen.dts
+++ b/arch/arm/boot/dts/exynos4210-origen.dts
@@ -32,6 +32,13 @@ 

+       l2-cache-controller@10502000 {
+               compatible = "arm,pl310-cache";
+               reg = <0x10502000 0x1000>;
+               cache-unified;
+               cache-level = <2>;
+       };
+

>> be a good time to get rid of the L2_AUX_VAL and L2_AUX_MASK defines and
>> just read the respective settings from DT.

Ok.