On Wed, May 25, 2011 at 21:13, Rajendra Nayak <rnayak@xxxxxx> wrote:
> On 5/26/2011 8:46 AM, Todd Poynor wrote:
>>
>> On Wed, May 25, 2011 at 06:56:56PM -0700, Nishanth Menon wrote:
>> ...
>>>
>>> @@ -427,6 +465,7 @@ int omap3_noncore_dpll_set_rate(struct clk *clk,
>>> unsigned long rate)
>>> u16 freqsel = 0;
>>> struct dpll_data *dd;
>>> int ret;
>>> + unsigned long orig_rate = 0;
>>>
>>> if (!clk || !rate)
>>> return -EINVAL;
>>> @@ -454,6 +493,19 @@ int omap3_noncore_dpll_set_rate(struct clk *clk,
>>> unsigned long rate)
>>> if (!ret)
>>> new_parent = dd->clk_bypass;
>>> } else {
>>> + /*
>>> + * On 4460, the MPU clk for frequencies higher than 1Ghz
>>> + * is sourced from CLKOUTX2_M3, instead of CLKOUT_M2,
>>> while
>>> + * value of M3 is fixed to 1. Hence for frequencies
>>> higher
>>> + * than 1 Ghz, lock the DPLL at half the rate so the
>>> + * CLKOUTX2_M3 then matches the requested rate.
>>> + */
>>> + if (cpu_is_omap446x()&& !strcmp(clk->name,
>>> "dpll_mpu_ck")
>>> + && (rate> 1000000000)) {
>>> + orig_rate = rate;
>>> + rate = rate/2;
>>> + }
>>> +
>>> if (dd->last_rounded_rate != rate)
>>> omap2_dpll_round_rate(clk, rate);
>>>
>>> @@ -468,6 +520,12 @@ int omap3_noncore_dpll_set_rate(struct clk *clk,
>>> unsigned long rate)
>>> WARN_ON(1);
>>> }
>>>
>>> + /* Set the rate back to original for book keeping*/
>>> + if (orig_rate) {
>>> + rate = orig_rate;
>>> + dd->last_rounded_rate = dd->last_rounded_rate *
>>> 2;
>>
>> Not sure why dd->last_rounded_rate is being adjusted here. Its
>> value was computed based on orig_rate/2, and this adjustment will
>> force the code above to call omap2_dpll_round_rate() every time
>> (because the * 2 value will never equal the / 2 value). I haven't
>> seen the value reported anywhere, so it doesn't seem necessary?
>
> Todd, I have to admit I have'nt even tested this patch myself on a 4460
> (I don't even have one) and I did mention this to Nishanth when I sent
> this out to him.
> You are right that playing with the last_rounded_rate is not a good
> idea, that was done thinking the omap3_noncore_dpll_program then uses
> it and it needs the orig_rate and not the /2. But that certainly
> causes the omap2_dpll_round_rate to get called every time.
> I need to work some more on this patch and certainly *test* it to
> work on a 4460.
Hmm.. I apologize, I had expected the bootloader I was using was
supposed to boot at highest frequency - I might have been
mistaken(expectation was to test without a DVFS framework). However,
that said, the interest here in RFC itself (beyond the point that it
is done wrongly - thanks for confirming), is to know if this is the
right place to handle it. Looping in Paul and Benoit as well for their
views on the approach taken.
Regards,
Nishanth Menon
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