Hi All,

On 05/09/2012 02:28 PM, Jon Hunter wrote:

[...]

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No hacking intended here, just getting the flags correct ;-)

So let me start from the beginning ...

1. I agree that for the EMU CD that the valid HW states are HW_AUTO and
SW_WKUP.

2. When the EMU CD is active (due to something like PMU), we want to
keep the CD in the SW_WKUP state, otherwise we can automatically
transition to idle and reset the IP (at least for omap4430).

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3. When the EMU CD is inactive, we want to keep the CD in the HW_AUTO
state because SW_SLEEP is NOT supported.

In the current code, we have the CLKDM_CAN_DISABLE_AUTO flag disabled
and the CLKDM_CAN_ENABLE_AUTO flag enabled. If CLKDM_CAN_ENABLE_AUTO is
set then the omap_pm_clkdms_setup() function will place the CD into
HW_AUTO regardless of CLKDM_CAN_DISABLE_AUTO, and the next time the
hwmod _enable() is called it is in the HW_AUTO state and so it is
allowed to idle. This is not what we want. Do you agree?

If I set CLKDM_CAN_DISABLE_AUTO flag and disable CLKDM_CAN_ENABLE_AUTO,
then I do not have the above problem.

To be honest, with you the more I look and test the code, the more
confused I am by the definition of the CLKDM_CAN_HWSUP ...

#define CLKDM_CAN_HWSUP	(CLKDM_CAN_ENABLE_AUTO | CLKDM_CAN_DISABLE_AUTO)

When I look at where these flags are used, I see that
CLKDM_CAN_ENABLE_AUTO is used in clkdm_allow_idle and
CLKDM_CAN_DISABLE_AUTO is used in clkdm_deny_idle. So this implies that ...

CLKDM_CAN_ENABLE_AUTO = Supports HW_AUTO state when CD is active
CLKDM_CAN_DISABLE_AUTO = Does NOT supports HW_AUTO state when CD is active

Are the above the correct definitions?

Not quite.

These flags describe the capabilities as defined in CLKTRCTRL field of
the CLKSTCTRL register (e.g. CM_EMU_CLKSTCTRL)

CLKDM_CAN_ENABLE_AUTO: IP supports HW_AUTO state (and it can be enabled)
CLKDM_CAN_DISABLE_AUTO: HW_AUTO feature can be disabled (a.k.a. NO_SLEEP)

Note that in OMAP4, the latter called NO_SLEEP in the TRM, but in OMAP3
it's described as "The automatic hardware-supervised mode is disabled"

Yeah, in fact this is the source of the current confusion for my point of view.

We chat about that with Paul some time back.
 
EMU CD does support HW_AUTO and SW_WKUP, so it means that if you want to disable the AUTO mode you can use the SW_WKUP.
Assuming that CLKDM_CAN_DISABLE_AUTO is equivalent to NO_SLEEP is thus not correct. In fact any state != HW_AUTO should be considered a non-automatic mode.
So EMU does support CLKDM_CAN_ENABLE_AUTO, CLKDM_CAN_DISABLE_AUTO and CLKDM_CAN_FORCE_WAKEUP.

But the way it is implemented does not really allow that, because disable hwsup imply setting state to OMAP34XX_CLKSTCTRL_DISABLE_AUTO.

void omap4_cminst_clkdm_disable_hwsup(u8 part, s16 inst, u16 cdoffs)
{
        _clktrctrl_write(OMAP34XX_CLKSTCTRL_DISABLE_AUTO, part, inst, cdoffs);
}

So if we want to allow that, some code change are needed in order to set the clkdm mode to OMAP34XX_CLKSTCTRL_FORCE_WAKEUP if OMAP34XX_CLKSTCTRL_DISABLE_AUTO is not supported.

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What is confusing to me is that the OMAP4 TRM doesn't list the NO_SLEEP
mode as supported by the EMU.   It seems to me that if the IP supports
HW_AUTO, it should be able to be enabled *and* disabled.

No, not really, this is mostly OMAP3 legacy, and we do have plan to remove these useless modes going forward. We can effectively disable AUTO mode by going to FORCE_WAKEUP.

- 0x0 NO_SLEEP A clock domain sleep transition is never initiated, irrespective of the hardware conditions.
- 0x1 SW_SLEEP A software-forced sleep transition. The transition is initiated when the associated hardware conditions are satisfied
- 0x2 SW_WKUP A software-forced clock domain wake-up transition is initiated, irrespective of the hardware conditions.
- 0x3 HW_AUTO Hardware-controlled automatic sleep and wake-up transition is initiated by the PRCM module when the associated hardware conditions are satisfied


On OMAP4, SW_SLEEP is equivalent to ENABLE_AUTO and 
NO_SLEEP is equivalent to SW_WKUP. There are some slight differences inside the HW, but in term of functionality this is mostly equivalent.


Bottom-line, if we fix the omap4_cminst_clkdm_disable_hwsup, we can consider that the EMU CD does support CLKDM_CAN_ENABLE_AUTO, CLKDM_CAN_DISABLE_AUTO and CLKDM_CAN_FORCE_WAKEUP, which is equivalent to CLKDM_CAN_HWSUP | CLKDM_CAN_FORCE_WAKEUP.

Per our discussion and just to re-iterate here for OMAP4+ devices, we
should have ...

CAN_DISABLE_AUTO 	--> SW_WKUP
CAN_ENABLE_AUTO		--> HW_AUTO
CAN_FORCE_WAKEUP	--> SW_WKUP
CAN_FORCE_SLEEP		--> HW_AUTO

Hence, the NO_SLEEP and SW_SLEEP should not be used for OMAP4+ (per the
equivalents highlighted above). At least that is the current theory :-)

I realise now the the l4cfg CD does not support SW_WKUP and so I guess
we still need NO_SLEEP in that case. So that would break the above
mapping and we would have to handle it in software.

I have posted my latest series here [1] based upon that from Will [2]
which attempts to fix the EMU CD based upon the inputs from this thread.
It is working on my omap4460 panda. Hopefully Ming and/or Will can also
test. I know that Ming is out this week but said he can test next week.

Cheers
Jon

[1] http://marc.info/?l=linux-omap&m=133659938028348&w=2
[2] git://git.kernel.org/pub/scm/linux/kernel/git/will/linux.git perf/omap4