[PATCH 1/3] arm64: Enable OPP

[PATCH 1/3] arm64: Enable OPP

[Mark Brown]

From: Mark Brown <broonie@linaro.org>

Some of the generic drivers used on ARM class systems use OPP so allow it
to be selected in Kconfig. No code is required for this, it is not clear
to me why there is config for this option.

Signed-off-by: Mark Brown <broonie@linaro.org>
---
 arch/arm64/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 8ccdd2646ae3..8256d6d09d33 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -2,6 +2,7 @@ config ARM64
 	def_bool y
 	select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
 	select ARCH_USE_CMPXCHG_LOCKREF
+	select ARCH_HAS_OPP
 	select ARCH_HAS_SG_CHAIN
 	select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
 	select ARCH_WANT_OPTIONAL_GPIOLIB
-- 
2.0.0.rc2

[PATCH 2/3] arm64: Add big.LITTLE switcher stub

[Mark Brown]

From: Mark Brown <broonie@linaro.org>

The big.LITTLE cpufreq driver is useful on arm64 big.LITTLE systems even
without IKS support since it implements support for clusters with shared
clocks (a common big.LITTLE configuration). In order to allow it to be
built provide the non-IKS stubs for arm64, enabling cpufreq with all the
cores available.

It may make sense to make an asm-generic version of these stubs instead but
given that there's only likely to be these two architectures using the code
and asm-generic stubs also need per architecture updates it's probably more
trouble than it's worth.

Signed-off-by: Mark Brown <broonie@linaro.org>
---
 arch/arm64/include/asm/bL_switcher.h | 54 ++++++++++++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)
 create mode 100644 arch/arm64/include/asm/bL_switcher.h

diff --git a/arch/arm64/include/asm/bL_switcher.h b/arch/arm64/include/asm/bL_switcher.h
new file mode 100644
index 000000000000..2bee500b7f54
--- /dev/null
+++ b/arch/arm64/include/asm/bL_switcher.h
@@ -0,0 +1,54 @@
+/*
+ * Based on the stubs for the ARM implementation which is:
+ *
+ * Created by:  Nicolas Pitre, April 2012
+ * Copyright:   (C) 2012-2013  Linaro Limited
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef ASM_BL_SWITCHER_H
+#define ASM_BL_SWITCHER_H
+
+#include <linux/notifier.h>
+#include <linux/types.h>
+
+typedef void (*bL_switch_completion_handler)(void *cookie);
+
+static inline int bL_switch_request(unsigned int cpu,
+				    unsigned int new_cluster_id)
+{
+	return -ENOTSUPP;
+}
+
+/*
+ * Register here to be notified about runtime enabling/disabling of
+ * the switcher.
+ *
+ * The notifier chain is called with the switcher activation lock held:
+ * the switcher will not be enabled or disabled during callbacks.
+ * Callbacks must not call bL_switcher_{get,put}_enabled().
+ */
+#define BL_NOTIFY_PRE_ENABLE	0
+#define BL_NOTIFY_POST_ENABLE	1
+#define BL_NOTIFY_PRE_DISABLE	2
+#define BL_NOTIFY_POST_DISABLE	3
+
+static inline int bL_switcher_register_notifier(struct notifier_block *nb)
+{
+	return 0;
+}
+
+static inline int bL_switcher_unregister_notifier(struct notifier_block *nb)
+{
+	return 0;
+}
+
+static inline bool bL_switcher_get_enabled(void) { return false; }
+static inline void bL_switcher_put_enabled(void) { }
+static inline int bL_switcher_trace_trigger(void) { return 0; }
+static inline int bL_switcher_get_logical_index(u32 mpidr) { return -EUNATCH; }
+
+#endif
-- 
2.0.0.rc2

[PATCH 2/3] arm64: Add big.LITTLE switcher stub

[Sudeep Holla]

Hi Mark,

On 09/05/14 17:40, Mark Brown wrote:
> From: Mark Brown <broonie@linaro.org>
>
> The big.LITTLE cpufreq driver is useful on arm64 big.LITTLE systems even
> without IKS support since it implements support for clusters with shared
> clocks (a common big.LITTLE configuration). In order to allow it to be
> built provide the non-IKS stubs for arm64, enabling cpufreq with all the
> cores available.
>

I am in process of using this driver for ARM64 and hit the same issue.
I don't like this approach at all. I too did similar changes/hacks which are
good for quick testing but not for upstream.

I would like to move all the switcher code out of the driver as extension.
Also the core driver should be made to work with any multi-clsuter platform not
just big-little(bL). bL is one of them and bL switcher support should an
extension of it.

The main reason for this is I see some non-bL multi-cluster platform support
getting added, this driver should ideally support that.

> It may make sense to make an asm-generic version of these stubs instead but
> given that there's only likely to be these two architectures using the code
> and asm-generic stubs also need per architecture updates it's probably more
> trouble than it's worth.
>

I would not take this approach too. As mentioned above if we can resolve it in
that way we may not require this.

Regards,
Sudeep

[PATCH 2/3] arm64: Add big.LITTLE switcher stub

[Mark Brown]

On Fri, May 09, 2014 at 06:05:56PM +0100, Sudeep Holla wrote:
> On 09/05/14 17:40, Mark Brown wrote:

> >From: Mark Brown <broonie@linaro.org>

> >The big.LITTLE cpufreq driver is useful on arm64 big.LITTLE systems even
> >without IKS support since it implements support for clusters with shared
> >clocks (a common big.LITTLE configuration). In order to allow it to be
> >built provide the non-IKS stubs for arm64, enabling cpufreq with all the
> >cores available.

> I am in process of using this driver for ARM64 and hit the same issue.
> I don't like this approach at all. I too did similar changes/hacks which are
> good for quick testing but not for upstream.

I'm not a big fan of this either, but then as I indicated on the cpufreq
bit of the series I'm not a massive fan of the way this is handled in
the first place on either ARM or ARMv8.  This at least gives us parity
between the two architectures (modulo IKS implementation) which is
progress especially given the fact that much of the work done on this
stuff is being done on 32 bit due to hardware availability.

Given that the code isn't invasive I think the expediency tradeoff is OK
for mainline, it's easy enough to get rid of when we come up with
something better but in the meaintine it helps actual systems work
better in mainline - if we didn't have the ARM implementation already I
think it'd be different but we do.

Perfect can be the enemy of good (or at least adequate), one of the
problems I'm seeing right now with convincing people to work with
mainline is that people are missing lots of important functionality when
they look at mainline.

> I would like to move all the switcher code out of the driver as extension.
> Also the core driver should be made to work with any multi-clsuter platform not
> just big-little(bL). bL is one of them and bL switcher support should an
> extension of it.

> The main reason for this is I see some non-bL multi-cluster platform support
> getting added, this driver should ideally support that.

It is not entirely clear to me what you mean by "this driver" or "the
core driver" in all the above, sorry.

Personally the solution I'd rather see is cpufreq-cpu0 extended to
handle shared clocks which would remove the need to use the big.LITTLE
driver on systems not doing IKS.  It isn't at all clear to me that
cpufreq should understand clusters (or much of anything other than
clocks) in the non-IKS case, the sharing of clocks between cores is not
directly connected to their clustering.  Clustering is important to the
scheduler and an understanding of the power and clock sharing
constraints that come along with clusters is going to be required there
as part of energy aware scheduling but I'm not seeing any obvious reason
for the frequency scaling driver to know about this, even with cpufreq
governors it's mostly the clock sharing.

For IKS where we're pairing the CPUs up and telling the kernel that
switching between the physical clusters is part of scaling the
"frequency" of the virtual cluster presented to the rest of the system
things are of course different and cpufreq does need to understand the
physical clusters.

Having multiple generic frequency scaling drivers feels wrong; there's
going to be code duplication between them and it doesn't seem like there
should be anything going on that we can't automatically figure out at
runtime.
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[PATCH 2/3] arm64: Add big.LITTLE switcher stub

[Sudeep Holla]

On 09/05/14 18:50, Mark Brown wrote:
> On Fri, May 09, 2014 at 06:05:56PM +0100, Sudeep Holla wrote:
>> On 09/05/14 17:40, Mark Brown wrote:
>
>>> From: Mark Brown <broonie@linaro.org>
>
>>> The big.LITTLE cpufreq driver is useful on arm64 big.LITTLE systems even
>>> without IKS support since it implements support for clusters with shared
>>> clocks (a common big.LITTLE configuration). In order to allow it to be
>>> built provide the non-IKS stubs for arm64, enabling cpufreq with all the
>>> cores available.
>
>> I am in process of using this driver for ARM64 and hit the same issue.
>> I don't like this approach at all. I too did similar changes/hacks which are
>> good for quick testing but not for upstream.
>
> I'm not a big fan of this either, but then as I indicated on the cpufreq
> bit of the series I'm not a massive fan of the way this is handled in
> the first place on either ARM or ARMv8.  This at least gives us parity
> between the two architectures (modulo IKS implementation) which is
> progress especially given the fact that much of the work done on this
> stuff is being done on 32 bit due to hardware availability.
>

OK good to know that you too agree that this is not a good approach.

> Given that the code isn't invasive I think the expediency tradeoff is OK
> for mainline, it's easy enough to get rid of when we come up with
> something better but in the meaintine it helps actual systems work
> better in mainline - if we didn't have the ARM implementation already I
> think it'd be different but we do.
>

I disagree, I don't see a real urgency for this on ARM64. Even on ARM32, no
single platform other than TC2 is using this(at least as I see in the mainline).

If some real platform that needs this support urgently, then we can think of
similar short-term solution as part of adding support for cpufreq on that
platform. Do you know any platform that needs this right now ?

> Perfect can be the enemy of good (or at least adequate), one of the
> problems I'm seeing right now with convincing people to work with
> mainline is that people are missing lots of important functionality when
> they look at mainline.
>

Ok fair enough. But we can take some time and see if we can workout better
solution rather than jumping to add interim solutions when is unlikely to be
used on any real platform.

>> I would like to move all the switcher code out of the driver as extension.
>> Also the core driver should be made to work with any multi-clsuter platform not
>> just big-little(bL). bL is one of them and bL switcher support should an
>> extension of it.
>
>> The main reason for this is I see some non-bL multi-cluster platform support
>> getting added, this driver should ideally support that.
>
> It is not entirely clear to me what you mean by "this driver" or "the
> core driver" in all the above, sorry.
>

I meant the core arm-big-little cpufreq driver.

> Personally the solution I'd rather see is cpufreq-cpu0 extended to
> handle shared clocks which would remove the need to use the big.LITTLE

Ideally yes. IIUC it has dependencies on CPU0 and I have not looked that
driver and all of its users to judge how feasible is that. At-least we can
have cpufreq-cpu0 for all single cluster systems w/o support for per-CPU DVFS
and another which can handle multi-cluster systems(with or w/o per-CPU DVFS).

Just a thought...

> driver on systems not doing IKS.  It isn't at all clear to me that
> cpufreq should understand clusters (or much of anything other than
> clocks) in the non-IKS case, the sharing of clocks between cores is not

Yes I agree, I had brought up this in one of the discussions around extending
OPP bindings. The cluster dependency needs to be removed and it should be
derived from the clocks.

> directly connected to their clustering.  Clustering is important to the
> scheduler and an understanding of the power and clock sharing
> constraints that come along with clusters is going to be required there
> as part of energy aware scheduling but I'm not seeing any obvious reason
> for the frequency scaling driver to know about this, even with cpufreq
> governors it's mostly the clock sharing.
>

Both CPUFreq and Energy aware scheduling need understanding of clock sharing. 
Both have similar goals(save power with little or no performance degradation), 
but EA scheduler will be more efficient(both in terms of power and performance).

Governors need this knowledge of sharing as it affects the load calculation.
(IIRC maximum load of all the cpu sharing clocks is taken)

> For IKS where we're pairing the CPUs up and telling the kernel that
> switching between the physical clusters is part of scaling the
> "frequency" of the virtual cluster presented to the rest of the system
> things are of course different and cpufreq does need to understand the
> physical clusters.
>
> Having multiple generic frequency scaling drivers feels wrong; there's
> going to be code duplication between them and it doesn't seem like there
> should be anything going on that we can't automatically figure out at
> runtime.
>

Completely agree with you.

Regards,
Sudeep

[PATCH 2/3] arm64: Add big.LITTLE switcher stub

[Mark Brown]

On Fri, May 09, 2014 at 07:57:55PM +0100, Sudeep Holla wrote:
> On 09/05/14 18:50, Mark Brown wrote:

> >Given that the code isn't invasive I think the expediency tradeoff is OK
> >for mainline, it's easy enough to get rid of when we come up with
> >something better but in the meaintine it helps actual systems work
> >better in mainline - if we didn't have the ARM implementation already I
> >think it'd be different but we do.

> I disagree, I don't see a real urgency for this on ARM64. Even on ARM32, no
> single platform other than TC2 is using this(at least as I see in the mainline).

> If some real platform that needs this support urgently, then we can think of
> similar short-term solution as part of adding support for cpufreq on that
> platform. Do you know any platform that needs this right now ?

There's the big.LITTLE Exynos devices, at least the 5410 has shipped in
product using IKS I believe and so should've been using the big.LITTLE
cpufreq driver to do the cluster switching; I think some 5420 systems
were doing the same.  Or reimplementing it which would just be sad.
There's some other non-public devices I am aware of - the whole reason I
wrote this series was for those.

> >Perfect can be the enemy of good (or at least adequate), one of the
> >problems I'm seeing right now with convincing people to work with
> >mainline is that people are missing lots of important functionality when
> >they look at mainline.

> Ok fair enough. But we can take some time and see if we can workout better
> solution rather than jumping to add interim solutions when is unlikely to be
> used on any real platform.

There are real users who want to use this fairly urgently.  I can't be
specific, sorry.

> >Personally the solution I'd rather see is cpufreq-cpu0 extended to
> >handle shared clocks which would remove the need to use the big.LITTLE

> Ideally yes. IIUC it has dependencies on CPU0 and I have not looked that
> driver and all of its users to judge how feasible is that. At-least we can
> have cpufreq-cpu0 for all single cluster systems w/o support for per-CPU DVFS
> and another which can handle multi-cluster systems(with or w/o per-CPU DVFS).

> Just a thought...

It's not clear to me that having multiple clusters should require a
different driver, the single cluster case is just a specialisation of
the multicluster one as far as I can see.  It's possible I'm missing
something though.

I have to confess I didn't look in detail at cpufreq-cpu0 to make sure
it's the best place to start from but it looks clean and does have the
regulator stuff, though it's probably better to say that the goal is to
merge that and the big.LITTLE driver.

> >directly connected to their clustering.  Clustering is important to the
> >scheduler and an understanding of the power and clock sharing
> >constraints that come along with clusters is going to be required there
> >as part of energy aware scheduling but I'm not seeing any obvious reason
> >for the frequency scaling driver to know about this, even with cpufreq
> >governors it's mostly the clock sharing.

> Both CPUFreq and Energy aware scheduling need understanding of clock
> sharing. Both have similar goals(save power with little or no performance
> degradation), but EA scheduler will be more efficient(both in terms of power
> and performance).

> Governors need this knowledge of sharing as it affects the load calculation.
> (IIRC maximum load of all the cpu sharing clocks is taken)

Yes, definitely with respect to the clocks - my point was more about the
clustering bit (which is related to but not 100% tied to clocks).
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[PATCH 2/3] arm64: Add big.LITTLE switcher stub

[Sudeep Holla]

On 09/05/14 20:29, Mark Brown wrote:
> On Fri, May 09, 2014 at 07:57:55PM +0100, Sudeep Holla wrote:
>> On 09/05/14 18:50, Mark Brown wrote:
>
>>> Given that the code isn't invasive I think the expediency tradeoff is OK
>>> for mainline, it's easy enough to get rid of when we come up with
>>> something better but in the meaintine it helps actual systems work
>>> better in mainline - if we didn't have the ARM implementation already I
>>> think it'd be different but we do.
>
>> I disagree, I don't see a real urgency for this on ARM64. Even on ARM32, no
>> single platform other than TC2 is using this(at least as I see in the mainline).
>
>> If some real platform that needs this support urgently, then we can think of
>> similar short-term solution as part of adding support for cpufreq on that
>> platform. Do you know any platform that needs this right now ?
>
> There's the big.LITTLE Exynos devices, at least the 5410 has shipped in
> product using IKS I believe and so should've been using the big.LITTLE
> cpufreq driver to do the cluster switching; I think some 5420 systems
> were doing the same.  Or reimplementing it which would just be sad.
> There's some other non-public devices I am aware of - the whole reason I
> wrote this series was for those.
>

Correct all these are 32-bit platforms which are now in process of upstreaming.
So far they had their own driver and never used the arm-big-little driver.
And this current series deals with 64-bit platforms.

>>> Perfect can be the enemy of good (or at least adequate), one of the
>>> problems I'm seeing right now with convincing people to work with
>>> mainline is that people are missing lots of important functionality when
>>> they look at mainline.
>
>> Ok fair enough. But we can take some time and see if we can workout better
>> solution rather than jumping to add interim solutions when is unlikely to be
>> used on any real platform.
>
> There are real users who want to use this fairly urgently.  I can't be
> specific, sorry.
>

That's fine, I understand. But the main argument is that if these platforms
will not add support for cpufreq upstream anytime soon, I don't see any value
in rushing to this short term solution.

>>> Personally the solution I'd rather see is cpufreq-cpu0 extended to
>>> handle shared clocks which would remove the need to use the big.LITTLE
>
>> Ideally yes. IIUC it has dependencies on CPU0 and I have not looked that
>> driver and all of its users to judge how feasible is that. At-least we can
>> have cpufreq-cpu0 for all single cluster systems w/o support for per-CPU DVFS
>> and another which can handle multi-cluster systems(with or w/o per-CPU DVFS).
>
>> Just a thought...
>
> It's not clear to me that having multiple clusters should require a
> different driver, the single cluster case is just a specialisation of
> the multicluster one as far as I can see.  It's possible I'm missing
> something though.
>

No you are correct, but that change would require lot of changes and testing.
So my proposal above is just first step to avoid any new drivers and then we
need to merge it with cpufreq-cpu0.

> I have to confess I didn't look in detail at cpufreq-cpu0 to make sure
> it's the best place to start from but it looks clean and does have the
> regulator stuff, though it's probably better to say that the goal is to
> merge that and the big.LITTLE driver.
>

Me either, hence I didn't want to comment much on merging everything to
cpufrq-cpu0. Need to understand all the platforms using it so that generic 
solution based on clocks continues to work.

>>> directly connected to their clustering.  Clustering is important to the
>>> scheduler and an understanding of the power and clock sharing
>>> constraints that come along with clusters is going to be required there
>>> as part of energy aware scheduling but I'm not seeing any obvious reason
>>> for the frequency scaling driver to know about this, even with cpufreq
>>> governors it's mostly the clock sharing.
>
>> Both CPUFreq and Energy aware scheduling need understanding of clock
>> sharing. Both have similar goals(save power with little or no performance
>> degradation), but EA scheduler will be more efficient(both in terms of power
>> and performance).
>
>> Governors need this knowledge of sharing as it affects the load calculation.
>> (IIRC maximum load of all the cpu sharing clocks is taken)
>
> Yes, definitely with respect to the clocks - my point was more about the
> clustering bit (which is related to but not 100% tied to clocks).
>

Ok, that makes sense.

Regards,
Sudeep

[PATCH 2/3] arm64: Add big.LITTLE switcher stub

[Mark Brown]

On Mon, May 12, 2014 at 09:34:04AM +0100, Sudeep Holla wrote:
> On 09/05/14 20:29, Mark Brown wrote:
> >On Fri, May 09, 2014 at 07:57:55PM +0100, Sudeep Holla wrote:

> >>If some real platform that needs this support urgently, then we can think of
> >>similar short-term solution as part of adding support for cpufreq on that
> >>platform. Do you know any platform that needs this right now ?

...
> >There's some other non-public devices I am aware of - the whole reason I
> >wrote this series was for those.

> Correct all these are 32-bit platforms which are now in process of upstreaming.
> So far they had their own driver and never used the arm-big-little driver.
> And this current series deals with 64-bit platforms.

Except for the non-public devices on the end of the list there :)

> >There are real users who want to use this fairly urgently.  I can't be
> >specific, sorry.

> That's fine, I understand. But the main argument is that if these platforms
> will not add support for cpufreq upstream anytime soon, I don't see any value
> in rushing to this short term solution.

This all gets a bit circular though - the more patches people have to
carry to make upstream useful to them less useful working with upstream
seems to them, meaning the devices are less likely to appear upstream at
all at least in any sort of complete form.  One out of tree patch being
required isn't going to be a deal breaker by itself but they all add up
to a perception that upstream isn't useful.

There's definitely some taste considerations with how far you go to
cater for such systems - in this case I'd say it's just tweaking Kconfig
to allow people to use code that's already present rather than adding
really new code (there's the stubs but they're pretty insubstantial)
which means upstream doesn't have to carry anything that wasn't there
already.
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[PATCH 2/3] arm64: Add big.LITTLE switcher stub

[Mark Hambleton]

> This all gets a bit circular though - the more patches people have to
> carry to make upstream useful to them less useful working with upstream
> seems to them, meaning the devices are less likely to appear upstream at
> all at least in any sort of complete form.  One out of tree patch being
> required isn't going to be a deal breaker by itself but they all add up
> to a perception that upstream isn't useful.
> 
> There's definitely some taste considerations with how far you go to
> cater for such systems - in this case I'd say it's just tweaking Kconfig
> to allow people to use code that's already present rather than adding
> really new code (there's the stubs but they're pretty insubstantial)
> which means upstream doesn't have to carry anything that wasn't there
> already.

Agree, with the original version of this patch I just put all the stubs in drivers/cpufreq/arm_big_little.h to get around needing to add files to arm64 (when it shouldn't need it). At least then the stubs were pretty local to the implementation and didn't require all of the ifdefs in the code (as Mark says that looks horrible).

Mark

[PATCH 2/3] arm64: Add big.LITTLE switcher stub

[Catalin Marinas]

On Fri, May 09, 2014 at 05:40:30PM +0100, Mark Brown wrote:
> From: Mark Brown <broonie@linaro.org>
> 
> The big.LITTLE cpufreq driver is useful on arm64 big.LITTLE systems even
> without IKS support since it implements support for clusters with shared
> clocks (a common big.LITTLE configuration). In order to allow it to be
> built provide the non-IKS stubs for arm64, enabling cpufreq with all the
> cores available.

Have you thought of patching the actual cpufreq driver? Are you adding
this code just to avoid compiler errors on arm64 with this driver?

> It may make sense to make an asm-generic version of these stubs instead

asm-generic/bL_switcher.h? I take it as a good joke ;)

> but
> given that there's only likely to be these two architectures using the code
> and asm-generic stubs also need per architecture updates it's probably more
> trouble than it's worth.

Exactly.

-- 
Catalin

[PATCH 2/3] arm64: Add big.LITTLE switcher stub

[Mark Brown]

On Fri, May 09, 2014 at 06:47:38PM +0100, Catalin Marinas wrote:
> On Fri, May 09, 2014 at 05:40:30PM +0100, Mark Brown wrote:

> > The big.LITTLE cpufreq driver is useful on arm64 big.LITTLE systems even
> > without IKS support since it implements support for clusters with shared
> > clocks (a common big.LITTLE configuration). In order to allow it to be
> > built provide the non-IKS stubs for arm64, enabling cpufreq with all the
> > cores available.

> Have you thought of patching the actual cpufreq driver? Are you adding
> this code just to avoid compiler errors on arm64 with this driver?

Yes, that was actually my first thought but I wasn't loving the
ifdeferry - it's fairly easy to do IIRC but the general taste seems to
be towards having stubs rather than ifdefs and the code seemed to be
lending itself to that.  There was also the fact that ifdefs could have
been done for the non-IKS case on 32 bit but instead stubs were
provided.  If people prefer I can do an ifdeffed version though, it
doesn't make much odds.

This was purely to get the driver compiling and hopefully running on
ARMv8, there is some user demand for deploying the driver on big.LITTLE
systems.

> > It may make sense to make an asm-generic version of these stubs instead

> asm-generic/bL_switcher.h? I take it as a good joke ;)

Hey, perhaps other hardware architectures are implementing similar
concepts even now in order to keep up!  :P
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[PATCH 2/3] arm64: Add big.LITTLE switcher stub

[Nicolas Pitre]

On Fri, 9 May 2014, Mark Brown wrote:

> On Fri, May 09, 2014 at 06:47:38PM +0100, Catalin Marinas wrote:
> > On Fri, May 09, 2014 at 05:40:30PM +0100, Mark Brown wrote:
> 
> > > The big.LITTLE cpufreq driver is useful on arm64 big.LITTLE systems even
> > > without IKS support since it implements support for clusters with shared
> > > clocks (a common big.LITTLE configuration). In order to allow it to be
> > > built provide the non-IKS stubs for arm64, enabling cpufreq with all the
> > > cores available.
> 
> > Have you thought of patching the actual cpufreq driver? Are you adding
> > this code just to avoid compiler errors on arm64 with this driver?
> 
> Yes, that was actually my first thought but I wasn't loving the
> ifdeferry - it's fairly easy to do IIRC but the general taste seems to
> be towards having stubs rather than ifdefs and the code seemed to be
> lending itself to that.  There was also the fact that ifdefs could have
> been done for the non-IKS case on 32 bit but instead stubs were
> provided.  If people prefer I can do an ifdeffed version though, it
> doesn't make much odds.

I personally don't understand the b.L cpufreq driver fully, especially 
with the IKS functionality bolted on top.  Obviously I didn't write that 
part otherwise I would hopefully understand it better.  Still, I'd have 
preferred for the IKS extension to the b.L cpufreq driver to be more 
isolated in a separate file or the like.

> This was purely to get the driver compiling and hopefully running on
> ARMv8, there is some user demand for deploying the driver on big.LITTLE
> systems.
> 
> > > It may make sense to make an asm-generic version of these stubs instead
> 
> > asm-generic/bL_switcher.h? I take it as a good joke ;)
> 
> Hey, perhaps other hardware architectures are implementing similar
> concepts even now in order to keep up!  

Let's hope we won't need to rely on IKS any longer by the time support 
for them land into mainline.


Nicolas

[PATCH 3/3] cpufreq: Enable big.LITTLE cpufreq driver on arm64

[Mark Brown]

From: Mark Brown <broonie@linaro.org>

There are arm64 big.LITTLE systems so enable the big.LITTLE cpufreq driver.
While IKS is not available for these systems the driver is still useful
since it manages clusters with shared frequencies which is the common case
for these systems.

Long term combining the cpufreq-cpu0 and big.LITTLE drivers may be a
more sensible option but that is substantially more complex especially
in the case of IKS.

Signed-off-by: Mark Brown <broonie@linaro.org>
---
 drivers/cpufreq/Kconfig.arm | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/cpufreq/Kconfig.arm b/drivers/cpufreq/Kconfig.arm
index 6e05a1e18e52..6a7dd3e958d5 100644
--- a/drivers/cpufreq/Kconfig.arm
+++ b/drivers/cpufreq/Kconfig.arm
@@ -5,7 +5,8 @@
 # big LITTLE core layer and glue drivers
 config ARM_BIG_LITTLE_CPUFREQ
 	tristate "Generic ARM big LITTLE CPUfreq driver"
-	depends on ARM && BIG_LITTLE && ARM_CPU_TOPOLOGY && HAVE_CLK
+	depends on (BIG_LITTLE && ARM_CPU_TOPOLOGY) || (ARM64 && SMP)
+	depends on HAVE_CLK
 	select PM_OPP
 	help
 	  This enables the Generic CPUfreq driver for ARM big.LITTLE platforms.
-- 
2.0.0.rc2

[PATCH 3/3] cpufreq: Enable big.LITTLE cpufreq driver on arm64

[Viresh Kumar]

On 9 May 2014 22:10, Mark Brown <broonie@kernel.org> wrote:
> From: Mark Brown <broonie@linaro.org>
>
> There are arm64 big.LITTLE systems so enable the big.LITTLE cpufreq driver.
> While IKS is not available for these systems the driver is still useful
> since it manages clusters with shared frequencies which is the common case
> for these systems.
>
> Long term combining the cpufreq-cpu0 and big.LITTLE drivers may be a
> more sensible option but that is substantially more complex especially
> in the case of IKS.

Yeah, it was left separately for IKS specially :(

> Signed-off-by: Mark Brown <broonie@linaro.org>
> ---
>  drivers/cpufreq/Kconfig.arm | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/cpufreq/Kconfig.arm b/drivers/cpufreq/Kconfig.arm
> index 6e05a1e18e52..6a7dd3e958d5 100644
> --- a/drivers/cpufreq/Kconfig.arm
> +++ b/drivers/cpufreq/Kconfig.arm
> @@ -5,7 +5,8 @@
>  # big LITTLE core layer and glue drivers
>  config ARM_BIG_LITTLE_CPUFREQ
>         tristate "Generic ARM big LITTLE CPUfreq driver"
> -       depends on ARM && BIG_LITTLE && ARM_CPU_TOPOLOGY && HAVE_CLK
> +       depends on (BIG_LITTLE && ARM_CPU_TOPOLOGY) || (ARM64 && SMP)
> +       depends on HAVE_CLK
>         select PM_OPP
>         help
>           This enables the Generic CPUfreq driver for ARM big.LITTLE platforms.

Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

[PATCH 3/3] cpufreq: Enable big.LITTLE cpufreq driver on arm64

[Rafael J. Wysocki]

On Monday, May 12, 2014 09:46:01 AM Viresh Kumar wrote:
> On 9 May 2014 22:10, Mark Brown <broonie@kernel.org> wrote:
> > From: Mark Brown <broonie@linaro.org>
> >
> > There are arm64 big.LITTLE systems so enable the big.LITTLE cpufreq driver.
> > While IKS is not available for these systems the driver is still useful
> > since it manages clusters with shared frequencies which is the common case
> > for these systems.
> >
> > Long term combining the cpufreq-cpu0 and big.LITTLE drivers may be a
> > more sensible option but that is substantially more complex especially
> > in the case of IKS.
> 
> Yeah, it was left separately for IKS specially :(
> 
> > Signed-off-by: Mark Brown <broonie@linaro.org>
> > ---
> >  drivers/cpufreq/Kconfig.arm | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/cpufreq/Kconfig.arm b/drivers/cpufreq/Kconfig.arm
> > index 6e05a1e18e52..6a7dd3e958d5 100644
> > --- a/drivers/cpufreq/Kconfig.arm
> > +++ b/drivers/cpufreq/Kconfig.arm
> > @@ -5,7 +5,8 @@
> >  # big LITTLE core layer and glue drivers
> >  config ARM_BIG_LITTLE_CPUFREQ
> >         tristate "Generic ARM big LITTLE CPUfreq driver"
> > -       depends on ARM && BIG_LITTLE && ARM_CPU_TOPOLOGY && HAVE_CLK
> > +       depends on (BIG_LITTLE && ARM_CPU_TOPOLOGY) || (ARM64 && SMP)
> > +       depends on HAVE_CLK
> >         select PM_OPP
> >         help
> >           This enables the Generic CPUfreq driver for ARM big.LITTLE platforms.
> 
> Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

I've queued this one up for 3.16, thanks!

> --
> To unsubscribe from this list: send the line "unsubscribe linux-pm" in
> the body of a message to majordomo at vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.

[PATCH 3/3] cpufreq: Enable big.LITTLE cpufreq driver on arm64

[Mark Brown]

On Tue, May 20, 2014 at 01:19:03AM +0200, Rafael J. Wysocki wrote:

> I've queued this one up for 3.16, thanks!

This will fail to build without patch 1 - it uses the stubs added there.
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[PATCH 3/3] cpufreq: Enable big.LITTLE cpufreq driver on arm64

[Rafael J. Wysocki]

On Tuesday, May 20, 2014 12:07:29 AM Mark Brown wrote:
> 
> --MAH+hnPXVZWQ5cD/
> Content-Type: text/plain; charset=us-ascii
> Content-Disposition: inline
> 
> On Tue, May 20, 2014 at 01:19:03AM +0200, Rafael J. Wysocki wrote:
> 
> > I've queued this one up for 3.16, thanks!
> 
> This will fail to build without patch 1 - it uses the stubs added there.

OK, dropping then.

Rafael

[PATCH 3/3] cpufreq: Enable big.LITTLE cpufreq driver on arm64

[Catalin Marinas]

Hi Rafael,

On Tue, May 20, 2014 at 12:36:56AM +0100, Rafael J. Wysocki wrote:
> On Tuesday, May 20, 2014 12:07:29 AM Mark Brown wrote:
> > 
> > --MAH+hnPXVZWQ5cD/
> > Content-Type: text/plain; charset=us-ascii
> > Content-Disposition: inline
> > 
> > On Tue, May 20, 2014 at 01:19:03AM +0200, Rafael J. Wysocki wrote:
> > 
> > > I've queued this one up for 3.16, thanks!
> > 
> > This will fail to build without patch 1 - it uses the stubs added there.
> 
> OK, dropping then.

This patch still made it as commit 4920ab84979d (cpufreq: Enable
big.LITTLE cpufreq driver on arm64) and fails to build on arm64. Could
you please revert it?

Thanks.

-- 
Catalin

[PATCH 3/3] cpufreq: Enable big.LITTLE cpufreq driver on arm64

[Rafael J. Wysocki]

On Thursday, June 05, 2014 11:04:16 AM Catalin Marinas wrote:
> Hi Rafael,
> 
> On Tue, May 20, 2014 at 12:36:56AM +0100, Rafael J. Wysocki wrote:
> > On Tuesday, May 20, 2014 12:07:29 AM Mark Brown wrote:
> > > 
> > > --MAH+hnPXVZWQ5cD/
> > > Content-Type: text/plain; charset=us-ascii
> > > Content-Disposition: inline
> > > 
> > > On Tue, May 20, 2014 at 01:19:03AM +0200, Rafael J. Wysocki wrote:
> > > 
> > > > I've queued this one up for 3.16, thanks!
> > > 
> > > This will fail to build without patch 1 - it uses the stubs added there.
> > 
> > OK, dropping then.
> 
> This patch still made it as commit 4920ab84979d (cpufreq: Enable
> big.LITTLE cpufreq driver on arm64) and fails to build on arm64. Could
> you please revert it?

I will.

Rafael

[PATCH 1/3] arm64: Enable OPP

[menon.nishanth at gmail.com]

On Fri, May 9, 2014 at 11:40 AM, Mark Brown <broonie@kernel.org> wrote:
> From: Mark Brown <broonie@linaro.org>
>
> Some of the generic drivers used on ARM class systems use OPP so allow it
> to be selected in Kconfig. No code is required for this, it is not clear
> to me why there is config for this option.
If you mean why we have ARCH_HAS_OPP,
http://lists-archives.com/linux-kernel/27401148-pm-hide-opp-configuration-when-socs-do-not-provide-an-implementation.html

>
> Signed-off-by: Mark Brown <broonie@linaro.org>
> ---
>  arch/arm64/Kconfig | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 8ccdd2646ae3..8256d6d09d33 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -2,6 +2,7 @@ config ARM64
>         def_bool y
>         select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
>         select ARCH_USE_CMPXCHG_LOCKREF
> +       select ARCH_HAS_OPP
>         select ARCH_HAS_SG_CHAIN
>         select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
>         select ARCH_WANT_OPTIONAL_GPIOLIB
> --
> 2.0.0.rc2
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-pm" in
> the body of a message to majordomo at vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

[PATCH 1/3] arm64: Enable OPP

[Mark Brown]

On Fri, May 09, 2014 at 12:02:12PM -0500, menon.nishanth at gmail.com wrote:
> On Fri, May 9, 2014 at 11:40 AM, Mark Brown <broonie@kernel.org> wrote:

> > Some of the generic drivers used on ARM class systems use OPP so allow it
> > to be selected in Kconfig. No code is required for this, it is not clear
> > to me why there is config for this option.

> If you mean why we have ARCH_HAS_OPP,
> http://lists-archives.com/linux-kernel/27401148-pm-hide-opp-configuration-when-socs-do-not-provide-an-implementation.html

That's for the user visible symbol but OPP is also enableable via select
- the fix here may be to remove both the visibility check and the
dependency.
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[PATCH 1/3] arm64: Enable OPP

[menon.nishanth at gmail.com]

On Fri, May 9, 2014 at 12:11 PM, Mark Brown <broonie@kernel.org> wrote:
> On Fri, May 09, 2014 at 12:02:12PM -0500, menon.nishanth at gmail.com wrote:
>> On Fri, May 9, 2014 at 11:40 AM, Mark Brown <broonie@kernel.org> wrote:
>
>> > Some of the generic drivers used on ARM class systems use OPP so allow it
>> > to be selected in Kconfig. No code is required for this, it is not clear
>> > to me why there is config for this option.
>
>> If you mean why we have ARCH_HAS_OPP,
>> http://lists-archives.com/linux-kernel/27401148-pm-hide-opp-configuration-when-socs-do-not-provide-an-implementation.html
>
> That's for the user visible symbol but OPP is also enableable via select
> - the fix here may be to remove both the visibility check and the
> dependency.
That is reasonable.
Regards,
Nishanth Menon

[PATCH 1/3] arm64: Enable OPP

[Mark Brown]

On Fri, May 09, 2014 at 12:17:23PM -0500, menon.nishanth at gmail.com wrote:
> On Fri, May 9, 2014 at 12:11 PM, Mark Brown <broonie@kernel.org> wrote:

> > That's for the user visible symbol but OPP is also enableable via select
> > - the fix here may be to remove both the visibility check and the
> > dependency.

> That is reasonable.

OK, I've sent a patch - now I look at what the OPP stuff is doing that
definitely seems like a better approach.
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