[PATCH v2 6/6] OMAP4: Clock: Correct the name of SLIMBUS interface clocks

[PATCH v2 6/6] OMAP4: Clock: Correct the name of SLIMBUS interface clocks

[Jon Hunter]

From: Jon Hunter <jon-hunter@ti.com>

Currently the interface clocks for the two SLIMBUS peripherals are
named slimbus1_fck and slimbus2_fck. Rename these clocks to be
slimbus1_ick and slimbus2_ick so it is clear that these are
interface clocks and not functional clocks.

Signed-off-by: Jon Hunter <jon-hunter@ti.com>
---
 arch/arm/mach-omap2/clock44xx_data.c |   12 ++++++------
 1 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/arch/arm/mach-omap2/clock44xx_data.c b/arch/arm/mach-omap2/clock44xx_data.c
index eb2a345..d75ebdd 100644
--- a/arch/arm/mach-omap2/clock44xx_data.c
+++ b/arch/arm/mach-omap2/clock44xx_data.c
@@ -2210,8 +2210,8 @@ static struct clk slimbus1_slimbus_clk = {
 	.recalc		= &followparent_recalc,
 };
 
-static struct clk slimbus1_fck = {
-	.name		= "slimbus1_fck",
+static struct clk slimbus1_ick = {
+	.name		= "slimbus1_ick",
 	.ops		= &clkops_omap2_dflt,
 	.enable_reg	= OMAP4430_CM1_ABE_SLIMBUS_CLKCTRL,
 	.enable_bit	= OMAP4430_MODULEMODE_SWCTRL,
@@ -2250,8 +2250,8 @@ static struct clk slimbus2_slimbus_clk = {
 	.recalc		= &followparent_recalc,
 };
 
-static struct clk slimbus2_fck = {
-	.name		= "slimbus2_fck",
+static struct clk slimbus2_ick = {
+	.name		= "slimbus2_ick",
 	.ops		= &clkops_omap2_dflt,
 	.enable_reg	= OMAP4430_CM_L4PER_SLIMBUS2_CLKCTRL,
 	.enable_bit	= OMAP4430_MODULEMODE_SWCTRL,
@@ -3272,11 +3272,11 @@ static struct omap_clk omap44xx_clks[] = {
 	CLK(NULL,	"slimbus1_fclk_0",		&slimbus1_fclk_0,	CK_443X),
 	CLK(NULL,	"slimbus1_fclk_2",		&slimbus1_fclk_2,	CK_443X),
 	CLK(NULL,	"slimbus1_slimbus_clk",		&slimbus1_slimbus_clk,	CK_443X),
-	CLK(NULL,	"slimbus1_fck",			&slimbus1_fck,	CK_443X),
+	CLK(NULL,	"slimbus1_ick",			&slimbus1_ick,	CK_443X),
 	CLK(NULL,	"slimbus2_fclk_1",		&slimbus2_fclk_1,	CK_443X),
 	CLK(NULL,	"slimbus2_fclk_0",		&slimbus2_fclk_0,	CK_443X),
 	CLK(NULL,	"slimbus2_slimbus_clk",		&slimbus2_slimbus_clk,	CK_443X),
-	CLK(NULL,	"slimbus2_fck",			&slimbus2_fck,	CK_443X),
+	CLK(NULL,	"slimbus2_ick",			&slimbus2_ick,	CK_443X),
 	CLK(NULL,	"smartreflex_core_fck",		&smartreflex_core_fck,	CK_443X),
 	CLK(NULL,	"smartreflex_iva_fck",		&smartreflex_iva_fck,	CK_443X),
 	CLK(NULL,	"smartreflex_mpu_fck",		&smartreflex_mpu_fck,	CK_443X),
-- 
1.7.4.1

[PATCH v2 6/6] OMAP4: Clock: Correct the name of SLIMBUS interface clocks

[Paul Walmsley]

+ Beno?t

On Fri, 16 Sep 2011, Jon Hunter wrote:

> From: Jon Hunter <jon-hunter@ti.com>
> 
> Currently the interface clocks for the two SLIMBUS peripherals are
> named slimbus1_fck and slimbus2_fck. Rename these clocks to be
> slimbus1_ick and slimbus2_ick so it is clear that these are
> interface clocks and not functional clocks.
> 
> Signed-off-by: Jon Hunter <jon-hunter@ti.com>

This one, I don't quite understand.  We should probably be removing these 
MODULEMODE-only clocks from the OMAP4 tree, and using their parent clock 
as the main_clk.  That would be a good cleanup for 3.3...


- Paul

[PATCH v2 6/6] OMAP4: Clock: Correct the name of SLIMBUS interface clocks

[Cousson, Benoit]

Hi Paul & Jon,

On 10/7/2011 3:42 AM, Paul Walmsley wrote:
> + Beno?t
>
> On Fri, 16 Sep 2011, Jon Hunter wrote:
>
>> From: Jon Hunter<jon-hunter@ti.com>
>>
>> Currently the interface clocks for the two SLIMBUS peripherals are
>> named slimbus1_fck and slimbus2_fck. Rename these clocks to be
>> slimbus1_ick and slimbus2_ick so it is clear that these are
>> interface clocks and not functional clocks.
>>
>> Signed-off-by: Jon Hunter<jon-hunter@ti.com>
>
> This one, I don't quite understand.  We should probably be removing these
> MODULEMODE-only clocks from the OMAP4 tree, and using their parent clock
> as the main_clk.  That would be a good cleanup for 3.3...

Yes, but in order to remove that from the clock data we must ensure that 
the hwmod entry is there.
I kept a lot of legacy MODULEMODE clocks just because of missing hwmod / 
runtime_pm adaptation on some drivers.

In the case of slimbus, there is no main_clk but a bunch of optional 
clocks. It looks similar to the DSS case. So we should not use the 
parent clock as a main_clk.

We should probably promote one of the opt_clk as the main_clk. The 
slimbus_clk seems to be the good candidate for both instances.

static struct omap_hwmod_opt_clk slimbus1_opt_clks[] = {
        { .role = "fclk_1", .clk = "slimbus1_fclk_1" },
        { .role = "fclk_0", .clk = "slimbus1_fclk_0" },
        { .role = "fclk_2", .clk = "slimbus1_fclk_2" },
        { .role = "slimbus_clk", .clk = "slimbus1_slimbus_clk" },
};

static struct omap_hwmod_opt_clk slimbus2_opt_clks[] = {
        { .role = "fclk_1", .clk = "slimbus2_fclk_1" },
        { .role = "fclk_0", .clk = "slimbus2_fclk_0" },
        { .role = "slimbus_clk", .clk = "slimbus2_slimbus_clk" },
};

Jon,
Do you know if that one is indeed mandatory to use the slimbus IP?

Thanks,
Benoit

[PATCH v2 6/6] OMAP4: Clock: Correct the name of SLIMBUS interface clocks

[Jon Hunter]

Hi Benoit,

On 10/7/2011 3:23, Cousson, Benoit wrote:
> Hi Paul & Jon,
>
> On 10/7/2011 3:42 AM, Paul Walmsley wrote:
>> + Beno?t
>>
>> On Fri, 16 Sep 2011, Jon Hunter wrote:
>>
>>> From: Jon Hunter<jon-hunter@ti.com>
>>>
>>> Currently the interface clocks for the two SLIMBUS peripherals are
>>> named slimbus1_fck and slimbus2_fck. Rename these clocks to be
>>> slimbus1_ick and slimbus2_ick so it is clear that these are
>>> interface clocks and not functional clocks.
>>>
>>> Signed-off-by: Jon Hunter<jon-hunter@ti.com>
>>
>> This one, I don't quite understand. We should probably be removing these
>> MODULEMODE-only clocks from the OMAP4 tree, and using their parent clock
>> as the main_clk. That would be a good cleanup for 3.3...
>
> Yes, but in order to remove that from the clock data we must ensure that
> the hwmod entry is there.
> I kept a lot of legacy MODULEMODE clocks just because of missing hwmod /
> runtime_pm adaptation on some drivers.
>
> In the case of slimbus, there is no main_clk but a bunch of optional
> clocks. It looks similar to the DSS case. So we should not use the
> parent clock as a main_clk.
>
> We should probably promote one of the opt_clk as the main_clk. The
> slimbus_clk seems to be the good candidate for both instances.
>
> static struct omap_hwmod_opt_clk slimbus1_opt_clks[] = {
> { .role = "fclk_1", .clk = "slimbus1_fclk_1" },
> { .role = "fclk_0", .clk = "slimbus1_fclk_0" },
> { .role = "fclk_2", .clk = "slimbus1_fclk_2" },
> { .role = "slimbus_clk", .clk = "slimbus1_slimbus_clk" },
> };
>
> static struct omap_hwmod_opt_clk slimbus2_opt_clks[] = {
> { .role = "fclk_1", .clk = "slimbus2_fclk_1" },
> { .role = "fclk_0", .clk = "slimbus2_fclk_0" },
> { .role = "slimbus_clk", .clk = "slimbus2_slimbus_clk" },
> };
>
> Jon,
> Do you know if that one is indeed mandatory to use the slimbus IP?

Sorry, are you asking about the clocks I was re-naming or the 
slimbus_clk you are referring to above?

Looking at the clock tree tool, the slimbus_clk is the actual external 
slimbus clock that can be generated by OMAP or by an external device.

The TRM states ...

"Most of the SLIMbus module runs off two main clocks: the L4 interface 
clock for the data input and output registers, and the control and 
status control registers; and the SLIMbus clock, taken from the serial 
interface (CLK line) for the SLIMbus-side logic.

The SLIMbus controller operates as clock source component (active 
framer), which drives the SLIMbus clock line CLK, or as clock receiver 
component, which gets its clock from the same CLK line."

So, if you are operating as the clock source component on the bus then 
one of the optional clocks to drive the peripheral logic and if you are 
the clock receiver then you use slimbus_clk.

Cheers
Jon

[PATCH v2 6/6] OMAP4: Clock: Correct the name of SLIMBUS interface clocks

[Cousson, Benoit]

Hi Jon,

On 10/8/2011 12:46 AM, Hunter, Jon wrote:
> Hi Benoit,
>
> On 10/7/2011 3:23, Cousson, Benoit wrote:
>> Hi Paul&  Jon,
>>
>> On 10/7/2011 3:42 AM, Paul Walmsley wrote:
>>> + Beno?t
>>>
>>> On Fri, 16 Sep 2011, Jon Hunter wrote:
>>>
>>>> From: Jon Hunter<jon-hunter@ti.com>
>>>>
>>>> Currently the interface clocks for the two SLIMBUS peripherals are
>>>> named slimbus1_fck and slimbus2_fck. Rename these clocks to be
>>>> slimbus1_ick and slimbus2_ick so it is clear that these are
>>>> interface clocks and not functional clocks.
>>>>
>>>> Signed-off-by: Jon Hunter<jon-hunter@ti.com>
>>>
>>> This one, I don't quite understand. We should probably be removing these
>>> MODULEMODE-only clocks from the OMAP4 tree, and using their parent clock
>>> as the main_clk. That would be a good cleanup for 3.3...
>>
>> Yes, but in order to remove that from the clock data we must ensure that
>> the hwmod entry is there.
>> I kept a lot of legacy MODULEMODE clocks just because of missing hwmod /
>> runtime_pm adaptation on some drivers.
>>
>> In the case of slimbus, there is no main_clk but a bunch of optional
>> clocks. It looks similar to the DSS case. So we should not use the
>> parent clock as a main_clk.
>>
>> We should probably promote one of the opt_clk as the main_clk. The
>> slimbus_clk seems to be the good candidate for both instances.
>>
>> static struct omap_hwmod_opt_clk slimbus1_opt_clks[] = {
>> { .role = "fclk_1", .clk = "slimbus1_fclk_1" },
>> { .role = "fclk_0", .clk = "slimbus1_fclk_0" },
>> { .role = "fclk_2", .clk = "slimbus1_fclk_2" },
>> { .role = "slimbus_clk", .clk = "slimbus1_slimbus_clk" },
>> };
>>
>> static struct omap_hwmod_opt_clk slimbus2_opt_clks[] = {
>> { .role = "fclk_1", .clk = "slimbus2_fclk_1" },
>> { .role = "fclk_0", .clk = "slimbus2_fclk_0" },
>> { .role = "slimbus_clk", .clk = "slimbus2_slimbus_clk" },
>> };
>>
>> Jon,
>> Do you know if that one is indeed mandatory to use the slimbus IP?
>
> Sorry, are you asking about the clocks I was re-naming or the
> slimbus_clk you are referring to above?

The clocks you are renaming should not exist at all, so I was referring 
to the real clocks that are all listed as optional clocks.

Usually we do need to have a main_clk in order to access the IP 
registers (at least the sysconfig). But for some IPs, the iclk can be 
enough.
If the interface clock is enough, then potentially that main clock is 
not mandatory. But if one functional clock is mandatory, then we have to 
figured out which one from the various optional functional clocks can be 
used as the main_clk.

> Looking at the clock tree tool, the slimbus_clk is the actual external
> slimbus clock that can be generated by OMAP or by an external device.
>
> The TRM states ...
>
> "Most of the SLIMbus module runs off two main clocks: the L4 interface
> clock for the data input and output registers, and the control and
> status control registers; and the SLIMbus clock, taken from the serial
> interface (CLK line) for the SLIMbus-side logic.
>
> The SLIMbus controller operates as clock source component (active
> framer), which drives the SLIMbus clock line CLK, or as clock receiver
> component, which gets its clock from the same CLK line."
>
> So, if you are operating as the clock source component on the bus then
> one of the optional clocks to drive the peripheral logic and if you are
> the clock receiver then you use slimbus_clk.

OK, so clearly, the slimbus_clk cannot be a main_clk. We have to check 
if the registers can be accessed only with the iclk.

Regards,
Benoit

[PATCH v2 6/6] OMAP4: Clock: Correct the name of SLIMBUS interface clocks

[Jon Hunter]

Hi Benoit,

On 10/10/2011 4:54, Cousson, Benoit wrote:
> Hi Jon,
>
> On 10/8/2011 12:46 AM, Hunter, Jon wrote:
>> Hi Benoit,
>>
>> On 10/7/2011 3:23, Cousson, Benoit wrote:
>>> Hi Paul& Jon,
>>>
>>> On 10/7/2011 3:42 AM, Paul Walmsley wrote:
>>>> + Beno?t
>>>>
>>>> On Fri, 16 Sep 2011, Jon Hunter wrote:
>>>>
>>>>> From: Jon Hunter<jon-hunter@ti.com>
>>>>>
>>>>> Currently the interface clocks for the two SLIMBUS peripherals are
>>>>> named slimbus1_fck and slimbus2_fck. Rename these clocks to be
>>>>> slimbus1_ick and slimbus2_ick so it is clear that these are
>>>>> interface clocks and not functional clocks.
>>>>>
>>>>> Signed-off-by: Jon Hunter<jon-hunter@ti.com>
>>>>
>>>> This one, I don't quite understand. We should probably be removing
>>>> these
>>>> MODULEMODE-only clocks from the OMAP4 tree, and using their parent
>>>> clock
>>>> as the main_clk. That would be a good cleanup for 3.3...
>>>
>>> Yes, but in order to remove that from the clock data we must ensure that
>>> the hwmod entry is there.
>>> I kept a lot of legacy MODULEMODE clocks just because of missing hwmod /
>>> runtime_pm adaptation on some drivers.
>>>
>>> In the case of slimbus, there is no main_clk but a bunch of optional
>>> clocks. It looks similar to the DSS case. So we should not use the
>>> parent clock as a main_clk.
>>>
>>> We should probably promote one of the opt_clk as the main_clk. The
>>> slimbus_clk seems to be the good candidate for both instances.
>>>
>>> static struct omap_hwmod_opt_clk slimbus1_opt_clks[] = {
>>> { .role = "fclk_1", .clk = "slimbus1_fclk_1" },
>>> { .role = "fclk_0", .clk = "slimbus1_fclk_0" },
>>> { .role = "fclk_2", .clk = "slimbus1_fclk_2" },
>>> { .role = "slimbus_clk", .clk = "slimbus1_slimbus_clk" },
>>> };
>>>
>>> static struct omap_hwmod_opt_clk slimbus2_opt_clks[] = {
>>> { .role = "fclk_1", .clk = "slimbus2_fclk_1" },
>>> { .role = "fclk_0", .clk = "slimbus2_fclk_0" },
>>> { .role = "slimbus_clk", .clk = "slimbus2_slimbus_clk" },
>>> };
>>>
>>> Jon,
>>> Do you know if that one is indeed mandatory to use the slimbus IP?
>>
>> Sorry, are you asking about the clocks I was re-naming or the
>> slimbus_clk you are referring to above?
>
> The clocks you are renaming should not exist at all, so I was referring
> to the real clocks that are all listed as optional clocks.

These clocks are the interface clocks enabled via the module-mode. So 
you are saying you want to remove the interface clocks from the list of 
clocks?

> Usually we do need to have a main_clk in order to access the IP
> registers (at least the sysconfig). But for some IPs, the iclk can be
> enough.
> If the interface clock is enough, then potentially that main clock is
> not mandatory. But if one functional clock is mandatory, then we have to
> figured out which one from the various optional functional clocks can be
> used as the main_clk.
>
>> Looking at the clock tree tool, the slimbus_clk is the actual external
>> slimbus clock that can be generated by OMAP or by an external device.
>>
>> The TRM states ...
>>
>> "Most of the SLIMbus module runs off two main clocks: the L4 interface
>> clock for the data input and output registers, and the control and
>> status control registers; and the SLIMbus clock, taken from the serial
>> interface (CLK line) for the SLIMbus-side logic.
>>
>> The SLIMbus controller operates as clock source component (active
>> framer), which drives the SLIMbus clock line CLK, or as clock receiver
>> component, which gets its clock from the same CLK line."
>>
>> So, if you are operating as the clock source component on the bus then
>> one of the optional clocks to drive the peripheral logic and if you are
>> the clock receiver then you use slimbus_clk.
>
> OK, so clearly, the slimbus_clk cannot be a main_clk. We have to check
> if the registers can be accessed only with the iclk.

I ran a quick test. If I just set the module mode to 0x2 (enabled), then 
I can access the registers. So no need to turn on any of the 
optional/functional clocks just the iclk.

Cheers
Jon

[PATCH v2 6/6] OMAP4: Clock: Correct the name of SLIMBUS interface clocks

[Cousson, Benoit]

On 10/10/2011 11:34 PM, Hunter, Jon wrote:
> Hi Benoit,
> 
> On 10/10/2011 4:54, Cousson, Benoit wrote:
>> Hi Jon,
>>
>> On 10/8/2011 12:46 AM, Hunter, Jon wrote:
>>> Hi Benoit,
>>>
>>> On 10/7/2011 3:23, Cousson, Benoit wrote:
>>>> Hi Paul&  Jon,
>>>>
>>>> On 10/7/2011 3:42 AM, Paul Walmsley wrote:
>>>>> + Beno?t
>>>>>
>>>>> On Fri, 16 Sep 2011, Jon Hunter wrote:
>>>>>
>>>>>> From: Jon Hunter<jon-hunter@ti.com>
>>>>>>
>>>>>> Currently the interface clocks for the two SLIMBUS peripherals are
>>>>>> named slimbus1_fck and slimbus2_fck. Rename these clocks to be
>>>>>> slimbus1_ick and slimbus2_ick so it is clear that these are
>>>>>> interface clocks and not functional clocks.
>>>>>>
>>>>>> Signed-off-by: Jon Hunter<jon-hunter@ti.com>
>>>>>
>>>>> This one, I don't quite understand. We should probably be removing
>>>>> these
>>>>> MODULEMODE-only clocks from the OMAP4 tree, and using their parent
>>>>> clock
>>>>> as the main_clk. That would be a good cleanup for 3.3...
>>>>
>>>> Yes, but in order to remove that from the clock data we must ensure that
>>>> the hwmod entry is there.
>>>> I kept a lot of legacy MODULEMODE clocks just because of missing hwmod /
>>>> runtime_pm adaptation on some drivers.
>>>>
>>>> In the case of slimbus, there is no main_clk but a bunch of optional
>>>> clocks. It looks similar to the DSS case. So we should not use the
>>>> parent clock as a main_clk.
>>>>
>>>> We should probably promote one of the opt_clk as the main_clk. The
>>>> slimbus_clk seems to be the good candidate for both instances.
>>>>
>>>> static struct omap_hwmod_opt_clk slimbus1_opt_clks[] = {
>>>> { .role = "fclk_1", .clk = "slimbus1_fclk_1" },
>>>> { .role = "fclk_0", .clk = "slimbus1_fclk_0" },
>>>> { .role = "fclk_2", .clk = "slimbus1_fclk_2" },
>>>> { .role = "slimbus_clk", .clk = "slimbus1_slimbus_clk" },
>>>> };
>>>>
>>>> static struct omap_hwmod_opt_clk slimbus2_opt_clks[] = {
>>>> { .role = "fclk_1", .clk = "slimbus2_fclk_1" },
>>>> { .role = "fclk_0", .clk = "slimbus2_fclk_0" },
>>>> { .role = "slimbus_clk", .clk = "slimbus2_slimbus_clk" },
>>>> };
>>>>
>>>> Jon,
>>>> Do you know if that one is indeed mandatory to use the slimbus IP?
>>>
>>> Sorry, are you asking about the clocks I was re-naming or the
>>> slimbus_clk you are referring to above?
>>
>> The clocks you are renaming should not exist at all, so I was referring
>> to the real clocks that are all listed as optional clocks.
> 
> These clocks are the interface clocks enabled via the module-mode. So
> you are saying you want to remove the interface clocks from the list of
> clocks?

Yes or No, dependeing of which clock you are talking about.
The real interface clock is already handled thanks to the ocp_if structure.

/* l4_abe -> slimbus1 */
static struct omap_hwmod_ocp_if omap44xx_l4_abe__slimbus1 = {
       .master         = &omap44xx_l4_abe_hwmod,
       .slave          = &omap44xx_slimbus1_hwmod,
       .clk            = "ocp_abe_iclk",
       .addr           = omap44xx_slimbus1_addrs,
       .user           = OCP_USER_MPU,
};

And since the modulemodule is now handled by the hwmod core thanks to that:

       .prcm = {
               .omap4 = {
                       .clkctrl_offs = OMAP4_CM1_ABE_SLIMBUS_CLKCTRL_OFFSET,
                       .context_offs = OMAP4_RM_ABE_SLIMBUS_CONTEXT_OFFSET,
                       .modulemode   = MODULEMODE_SWCTRL,
               },
       },

There is no need to create a fake leaf clock to handle the module using the clock fmwk.


So we can now remove these two clock nodes from the clock44xx_data.c file:

static struct clk slimbus1_fck = {
	.name		= "slimbus1_fck",
	.ops		= &clkops_omap2_dflt,
	.enable_reg	= OMAP4430_CM1_ABE_SLIMBUS_CLKCTRL,
	.enable_bit	= OMAP4430_MODULEMODE_SWCTRL,
	.clkdm_name	= "abe_clkdm",
	.parent		= &ocp_abe_iclk,
	.recalc		= &followparent_recalc,
};

static struct clk slimbus2_fck = {
	.name		= "slimbus2_fck",
	.ops		= &clkops_omap2_dflt,
	.enable_reg	= OMAP4430_CM_L4PER_SLIMBUS2_CLKCTRL,
	.enable_bit	= OMAP4430_MODULEMODE_SWCTRL,
	.clkdm_name	= "l4_per_clkdm",
	.parent		= &l4_div_ck,
	.recalc		= &followparent_recalc,
};

>> Usually we do need to have a main_clk in order to access the IP
>> registers (at least the sysconfig). But for some IPs, the iclk can be
>> enough.
>> If the interface clock is enough, then potentially that main clock is
>> not mandatory. But if one functional clock is mandatory, then we have to
>> figured out which one from the various optional functional clocks can be
>> used as the main_clk.
>>
>>> Looking at the clock tree tool, the slimbus_clk is the actual external
>>> slimbus clock that can be generated by OMAP or by an external device.
>>>
>>> The TRM states ...
>>>
>>> "Most of the SLIMbus module runs off two main clocks: the L4 interface
>>> clock for the data input and output registers, and the control and
>>> status control registers; and the SLIMbus clock, taken from the serial
>>> interface (CLK line) for the SLIMbus-side logic.
>>>
>>> The SLIMbus controller operates as clock source component (active
>>> framer), which drives the SLIMbus clock line CLK, or as clock receiver
>>> component, which gets its clock from the same CLK line."
>>>
>>> So, if you are operating as the clock source component on the bus then
>>> one of the optional clocks to drive the peripheral logic and if you are
>>> the clock receiver then you use slimbus_clk.
>>
>> OK, so clearly, the slimbus_clk cannot be a main_clk. We have to check
>> if the registers can be accessed only with the iclk.
> 
> I ran a quick test. If I just set the module mode to 0x2 (enabled), then
> I can access the registers. So no need to turn on any of the
> optional/functional clocks just the iclk.

That's good, so it looks like you will not have to populate the main_clk at all.

Regards,
Benoit