[PATCH] AM33XX: Clock: Fix JTAG disconnect during kernel boot

[PATCH] AM33XX: Clock: Fix JTAG disconnect during kernel boot

[Joel A Fernandes]

Set ENABLE_ON_INIT for debugss clock so that it is on during init and the usecount is incremented.
Not doing so causes kernel to disable debugss clock to save power when CONFIG_OMAP_RESET_CLOCKS
is set, causing a JTAG disconnect.

Signed-off-by: Joel A Fernandes <joelagnel@ti.com>
Cc: Russ Dill <Russ.Dill@ti.com>
Cc: Matt Porter <mporter@ti.com>
Cc: Steve Kipisz <s-kipisz2@ti.com>
Cc: Jason Kridner <jkridner@beagleboard.org>
Cc: Tony Lindgren <tony@atomide.com>
---
 arch/arm/mach-omap2/clock33xx_data.c |    1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm/mach-omap2/clock33xx_data.c b/arch/arm/mach-omap2/clock33xx_data.c
index b7b7995..d0b4313 100644
--- a/arch/arm/mach-omap2/clock33xx_data.c
+++ b/arch/arm/mach-omap2/clock33xx_data.c
@@ -585,6 +585,7 @@ static struct clk debugss_ick = {
 	.clkdm_name	= "l3_aon_clkdm",
 	.parent		= &dpll_core_m4_ck,
 	.ops		= &clkops_omap2_dflt,
+	.flags		= ENABLE_ON_INIT,
 	.enable_reg	= AM33XX_CM_WKUP_DEBUGSS_CLKCTRL,
 	.enable_bit	= AM33XX_MODULEMODE_SWCTRL,
 	.recalc		= &followparent_recalc,
-- 
1.7.9.5

[PATCH] AM33XX: Clock: Fix JTAG disconnect during kernel boot

[Joel A Fernandes]

Set ENABLE_ON_INIT for debugss clock so that it is on during init and the usecount is incremented.
Not doing so causes kernel to disable debugss clock to save power when CONFIG_OMAP_RESET_CLOCKS
is set, causing a JTAG disconnect.

Signed-off-by: Joel A Fernandes <joelagnel@ti.com>
Cc: Russ Dill <Russ.Dill@ti.com>
Cc: Matt Porter <mporter@ti.com>
Cc: Steve Kipisz <s-kipisz2@ti.com>
Cc: Jason Kridner <jkridner@beagleboard.org>
Cc: Tony Lindgren <tony@atomide.com>
---
Resending, as Cc list was dropped.

 arch/arm/mach-omap2/clock33xx_data.c |    1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm/mach-omap2/clock33xx_data.c b/arch/arm/mach-omap2/clock33xx_data.c
index b7b7995..d0b4313 100644
--- a/arch/arm/mach-omap2/clock33xx_data.c
+++ b/arch/arm/mach-omap2/clock33xx_data.c
@@ -585,6 +585,7 @@ static struct clk debugss_ick = {
 	.clkdm_name	= "l3_aon_clkdm",
 	.parent		= &dpll_core_m4_ck,
 	.ops		= &clkops_omap2_dflt,
+	.flags		= ENABLE_ON_INIT,
 	.enable_reg	= AM33XX_CM_WKUP_DEBUGSS_CLKCTRL,
 	.enable_bit	= AM33XX_MODULEMODE_SWCTRL,
 	.recalc		= &followparent_recalc,
-- 
1.7.9.5

Re: [PATCH] AM33XX: Clock: Fix JTAG disconnect during kernel boot

[Jon Hunter]

On 11/16/2012 05:44 PM, Joel A Fernandes wrote:
> Set ENABLE_ON_INIT for debugss clock so that it is on during init and the usecount is incremented.
> Not doing so causes kernel to disable debugss clock to save power when CONFIG_OMAP_RESET_CLOCKS
> is set, causing a JTAG disconnect.
> 
> Signed-off-by: Joel A Fernandes <joelagnel@ti.com>
> Cc: Russ Dill <Russ.Dill@ti.com>
> Cc: Matt Porter <mporter@ti.com>
> Cc: Steve Kipisz <s-kipisz2@ti.com>
> Cc: Jason Kridner <jkridner@beagleboard.org>
> Cc: Tony Lindgren <tony@atomide.com>
> ---
> Resending, as Cc list was dropped.
> 
>  arch/arm/mach-omap2/clock33xx_data.c |    1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/arm/mach-omap2/clock33xx_data.c b/arch/arm/mach-omap2/clock33xx_data.c
> index b7b7995..d0b4313 100644
> --- a/arch/arm/mach-omap2/clock33xx_data.c
> +++ b/arch/arm/mach-omap2/clock33xx_data.c
> @@ -585,6 +585,7 @@ static struct clk debugss_ick = {
>  	.clkdm_name	= "l3_aon_clkdm",
>  	.parent		= &dpll_core_m4_ck,
>  	.ops		= &clkops_omap2_dflt,
> +	.flags		= ENABLE_ON_INIT,
>  	.enable_reg	= AM33XX_CM_WKUP_DEBUGSS_CLKCTRL,
>  	.enable_bit	= AM33XX_MODULEMODE_SWCTRL,
>  	.recalc		= &followparent_recalc,

Does this mean this clock will always be enabled, even when not using
JTAG? If so, is that what you want?

I was not sure if you are concerned about power at all. Or if having
that always enabled can inhibit low power states for suspend/idle etc.

May be worth adding more details to the changelog about if there are
side-effects to this change or not.

Adding Paul as he is the maintainer of clocks and clock data.

Cheers
Jon

Re: [PATCH] AM33XX: Clock: Fix JTAG disconnect during kernel boot

[Joel A Fernandes]

Hi Jon,

On Fri, Nov 16, 2012 at 6:12 PM, Jon Hunter <jon-hunter@ti.com> wrote:
> > diff --git a/arch/arm/mach-omap2/clock33xx_data.c
> > b/arch/arm/mach-omap2/clock33xx_data.c
> > index b7b7995..d0b4313 100644
> > --- a/arch/arm/mach-omap2/clock33xx_data.c
> > +++ b/arch/arm/mach-omap2/clock33xx_data.c
> > @@ -585,6 +585,7 @@ static struct clk debugss_ick = {
> >       .clkdm_name     = "l3_aon_clkdm",
> >       .parent         = &dpll_core_m4_ck,
> >       .ops            = &clkops_omap2_dflt,
> > +     .flags          = ENABLE_ON_INIT,
> >       .enable_reg     = AM33XX_CM_WKUP_DEBUGSS_CLKCTRL,
> >       .enable_bit     = AM33XX_MODULEMODE_SWCTRL,
> >       .recalc         = &followparent_recalc,
>
> Does this mean this clock will always be enabled, even when not using
> JTAG? If so, is that what you want?

Yes, the clock will always be on, because some times we connect JTAG
on a running Linux system without powering it down. I can't comment
without doing measurements if keeping the clock on has significant
impact on power, but I see what you mean. Definitely low power is a
parameter and folks who want lowest possible power might need to turn
off the clock and not have JTAG in production, but that depends on the
user's requirement. I personally don't care about power as much as I
care about not being able to JTAG, and I think there are other folks
who suffer from the same JTAG problem who wouldn't necessarily want
lowest power.

> I was not sure if you are concerned about power at all. Or if having
> that always enabled can inhibit low power states for suspend/idle etc.

Maybe, suspend/resume code can turn off clock on suspend and enable it
on resume.

> May be worth adding more details to the changelog about if there are
> side-effects to this change or not.

Sure, will do after waiting for any other review comments.

Thanks,
Joel

Re: [PATCH] AM33XX: Clock: Fix JTAG disconnect during kernel boot

[Jon Hunter]

On 11/16/2012 08:44 PM, Joel A Fernandes wrote:
> Hi Jon,
> 
> On Fri, Nov 16, 2012 at 6:12 PM, Jon Hunter <jon-hunter@ti.com> wrote:
>>> diff --git a/arch/arm/mach-omap2/clock33xx_data.c
>>> b/arch/arm/mach-omap2/clock33xx_data.c
>>> index b7b7995..d0b4313 100644
>>> --- a/arch/arm/mach-omap2/clock33xx_data.c
>>> +++ b/arch/arm/mach-omap2/clock33xx_data.c
>>> @@ -585,6 +585,7 @@ static struct clk debugss_ick = {
>>>       .clkdm_name     = "l3_aon_clkdm",
>>>       .parent         = &dpll_core_m4_ck,
>>>       .ops            = &clkops_omap2_dflt,
>>> +     .flags          = ENABLE_ON_INIT,
>>>       .enable_reg     = AM33XX_CM_WKUP_DEBUGSS_CLKCTRL,
>>>       .enable_bit     = AM33XX_MODULEMODE_SWCTRL,
>>>       .recalc         = &followparent_recalc,
>>
>> Does this mean this clock will always be enabled, even when not using
>> JTAG? If so, is that what you want?
> 
> Yes, the clock will always be on, because some times we connect JTAG
> on a running Linux system without powering it down. I can't comment
> without doing measurements if keeping the clock on has significant
> impact on power, but I see what you mean. Definitely low power is a
> parameter and folks who want lowest possible power might need to turn
> off the clock and not have JTAG in production, but that depends on the
> user's requirement. I personally don't care about power as much as I
> care about not being able to JTAG, and I think there are other folks
> who suffer from the same JTAG problem who wouldn't necessarily want
> lowest power.

I can't say I am that familiar with the AM33xx architecture, but I know
that on OMAP this would keep on the debugss clock and power domain.

Do you need this change to connect JTAG after the kernel has booted or
just to maintain JTAG during kernel boot?

I am wondering if you should implement a new flag such as
"DONT_DISABLE_ON_INIT" so if the clock is on it is not disabled, but if
it is not enabled, you don't enabled it. Then that would be the best of
both worlds.

>> I was not sure if you are concerned about power at all. Or if having
>> that always enabled can inhibit low power states for suspend/idle etc.
> 
> Maybe, suspend/resume code can turn off clock on suspend and enable it
> on resume.

Yes, but not ideal for a product assuming they are power sensitive.

Cheers
Jon

Re: [PATCH] AM33XX: Clock: Fix JTAG disconnect during kernel boot

[Vaibhav Hiremath]

On 11/19/2012 9:45 PM, Jon Hunter wrote:
> 
> On 11/16/2012 08:44 PM, Joel A Fernandes wrote:
>> Hi Jon,
>>
>> On Fri, Nov 16, 2012 at 6:12 PM, Jon Hunter <jon-hunter@ti.com> wrote:
>>>> diff --git a/arch/arm/mach-omap2/clock33xx_data.c
>>>> b/arch/arm/mach-omap2/clock33xx_data.c
>>>> index b7b7995..d0b4313 100644
>>>> --- a/arch/arm/mach-omap2/clock33xx_data.c
>>>> +++ b/arch/arm/mach-omap2/clock33xx_data.c
>>>> @@ -585,6 +585,7 @@ static struct clk debugss_ick = {
>>>>       .clkdm_name     = "l3_aon_clkdm",
>>>>       .parent         = &dpll_core_m4_ck,
>>>>       .ops            = &clkops_omap2_dflt,
>>>> +     .flags          = ENABLE_ON_INIT,
>>>>       .enable_reg     = AM33XX_CM_WKUP_DEBUGSS_CLKCTRL,
>>>>       .enable_bit     = AM33XX_MODULEMODE_SWCTRL,
>>>>       .recalc         = &followparent_recalc,
>>>
>>> Does this mean this clock will always be enabled, even when not using
>>> JTAG? If so, is that what you want?
>>
>> Yes, the clock will always be on, because some times we connect JTAG
>> on a running Linux system without powering it down. I can't comment
>> without doing measurements if keeping the clock on has significant
>> impact on power, but I see what you mean. Definitely low power is a
>> parameter and folks who want lowest possible power might need to turn
>> off the clock and not have JTAG in production, but that depends on the
>> user's requirement. I personally don't care about power as much as I
>> care about not being able to JTAG, and I think there are other folks
>> who suffer from the same JTAG problem who wouldn't necessarily want
>> lowest power.
> 
> I can't say I am that familiar with the AM33xx architecture, but I know
> that on OMAP this would keep on the debugss clock and power domain.
> 
> Do you need this change to connect JTAG after the kernel has booted or
> just to maintain JTAG during kernel boot?
> 
> I am wondering if you should implement a new flag such as
> "DONT_DISABLE_ON_INIT" so if the clock is on it is not disabled, but if
> it is not enabled, you don't enabled it. Then that would be the best of
> both worlds.
> 

Joel,

The it should be handled is, on kernel_debug option we should keep it
enabled and default it should be disabled.

Something similar to,



diff --git a/arch/arm/mach-omap2/clock33xx_data.c
b/arch/arm/mach-omap2/clock33xx_data.c
index 17e3de5..60e0b53 100644
--- a/arch/arm/mach-omap2/clock33xx_data.c
+++ b/arch/arm/mach-omap2/clock33xx_data.c
@@ -584,6 +584,9 @@ static struct clk debugss_ick = {
        .clkdm_name     = "l3_aon_clkdm",
        .parent         = &dpll_core_m4_ck,
        .ops            = &clkops_omap2_dflt,
+#ifdef CONFIG_DEBUG_KERNEL
+       .flags          = ENABLE_ON_INIT,
+#endif
        .enable_reg     = AM33XX_CM_WKUP_DEBUGSS_CLKCTRL,
        .enable_bit     = AM33XX_MODULEMODE_SWCTRL,
        .recalc         = &followparent_recalc,


Can you please test above change??

Thanks,
Vaibhav
>>> I was not sure if you are concerned about power at all. Or if having
>>> that always enabled can inhibit low power states for suspend/idle etc.
>>
>> Maybe, suspend/resume code can turn off clock on suspend and enable it
>> on resume.
> 
> Yes, but not ideal for a product assuming they are power sensitive.
> 
> Cheers
> Jon
> --
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> 

Re: [PATCH] AM33XX: Clock: Fix JTAG disconnect during kernel boot

[Joel A Fernandes]

Hi Jon,

On Mon, Nov 19, 2012 at 10:15 AM, Jon Hunter <jon-hunter@ti.com> wrote:
>
> On 11/16/2012 08:44 PM, Joel A Fernandes wrote:
>> Hi Jon,
>>
>> On Fri, Nov 16, 2012 at 6:12 PM, Jon Hunter <jon-hunter@ti.com> wrote:
>>>> diff --git a/arch/arm/mach-omap2/clock33xx_data.c
>>>> b/arch/arm/mach-omap2/clock33xx_data.c
>>>> index b7b7995..d0b4313 100644
>>>> --- a/arch/arm/mach-omap2/clock33xx_data.c
>>>> +++ b/arch/arm/mach-omap2/clock33xx_data.c
>>>> @@ -585,6 +585,7 @@ static struct clk debugss_ick = {
>>>>       .clkdm_name     = "l3_aon_clkdm",
>>>>       .parent         = &dpll_core_m4_ck,
>>>>       .ops            = &clkops_omap2_dflt,
>>>> +     .flags          = ENABLE_ON_INIT,
>>>>       .enable_reg     = AM33XX_CM_WKUP_DEBUGSS_CLKCTRL,
>>>>       .enable_bit     = AM33XX_MODULEMODE_SWCTRL,
>>>>       .recalc         = &followparent_recalc,
>>>
>>> Does this mean this clock will always be enabled, even when not using
>>> JTAG? If so, is that what you want?
>>
>> Yes, the clock will always be on, because some times we connect JTAG
>> on a running Linux system without powering it down. I can't comment
>> without doing measurements if keeping the clock on has significant
>> impact on power, but I see what you mean. Definitely low power is a
>> parameter and folks who want lowest possible power might need to turn
>> off the clock and not have JTAG in production, but that depends on the
>> user's requirement. I personally don't care about power as much as I
>> care about not being able to JTAG, and I think there are other folks
>> who suffer from the same JTAG problem who wouldn't necessarily want
>> lowest power.
>
> I can't say I am that familiar with the AM33xx architecture, but I know
> that on OMAP this would keep on the debugss clock and power domain.
>
> Do you need this change to connect JTAG after the kernel has booted or
> just to maintain JTAG during kernel boot?

Actually both, only early stages of boot will have JTAG otherwise and
it shuts off pretty quickly.

> I am wondering if you should implement a new flag such as
> "DONT_DISABLE_ON_INIT" so if the clock is on it is not disabled, but if
> it is not enabled, you don't enabled it. Then that would be the best of
> both worlds.

I agree this is better. But the usecount element in the clock
structure would need to increment so it is known that the clock is in
use.

>>> I was not sure if you are concerned about power at all. Or if having
>>> that always enabled can inhibit low power states for suspend/idle etc.
>>
>> Maybe, suspend/resume code can turn off clock on suspend and enable it
>> on resume.
>
> Yes, but not ideal for a product assuming they are power sensitive.

Yes, true. It should be turned off when not required. Vaibhav made
suggestion where flag is wrapped in a kernel debug config option.

Regards,
Joel

Re: [PATCH] AM33XX: Clock: Fix JTAG disconnect during kernel boot

[Joel A Fernandes]

Hi Vaibhav,

> The it should be handled is, on kernel_debug option we should keep it
> enabled and default it should be disabled.
>
> Something similar to,
>
>
>
> diff --git a/arch/arm/mach-omap2/clock33xx_data.c
> b/arch/arm/mach-omap2/clock33xx_data.c
> index 17e3de5..60e0b53 100644
> --- a/arch/arm/mach-omap2/clock33xx_data.c
> +++ b/arch/arm/mach-omap2/clock33xx_data.c
> @@ -584,6 +584,9 @@ static struct clk debugss_ick = {
>         .clkdm_name     = "l3_aon_clkdm",
>         .parent         = &dpll_core_m4_ck,
>         .ops            = &clkops_omap2_dflt,
> +#ifdef CONFIG_DEBUG_KERNEL
> +       .flags          = ENABLE_ON_INIT,
> +#endif

Yes, looks like its a good idea to wrap the flag around a config
option, but I see you posted another patch where hwmod data is changed
for debugss_ick and Igor reported it to be working. Either approach is
ok with me.

Regards,
Joel