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

[Jon Hunter <jon-hunter@ti.com>]

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:
>>>> + Benoît
>>>>
>>>> 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
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