linux-kernel - Re: [PATCH] cpufreq: imx6q: support frequencies >528MHz for i.MX6UL/ULL

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Message-ID: <fedd9d818b58e5c19ad3201e68a1e55e@agner.ch>
Date:   Fri, 09 Feb 2018 13:05:27 +0100
From:   Stefan Agner <stefan@...er.ch>
To:     fabio.estevam@....com, leonard.crestez@....com
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>, viresh.kumar@...aro.org,
        shawnguo@...nel.org, octavian.purdila@....com,
        max.oss.09@...il.com, marcel.ziswiler@...adex.com,
        linux-pm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cpufreq: imx6q: support frequencies >528MHz for
 i.MX6UL/ULL

On 09.02.2018 12:52, Rafael J. Wysocki wrote:
> On Friday, January 19, 2018 12:58:36 AM CET Stefan Agner wrote:
>> Depending on SKU i.MX6UL/i.MX6ULL support frequencies up to 900MHz.
>> Use PLL1 sys clock for all operating points higher than 528MHz.
>>
>> Note: For higher operating points VDD_SOC_IN needs to be 125mV
>> higher than the ARM set-point (see datasheet). Specifically, the
>> i.MX6UL/ULL EVK boards have an external DC regulator which needs
>> adjustment. The regulator adjustment is not covered with this
>> change.
>>
>> Signed-off-by: Stefan Agner <stefan@...er.ch>
> 
> This makes sense to me, but I need someone with the requisite platform
> knowledge to review it.
> 

Fabio, Leonard, maybe one of you could have a look at it?

It is similar to what ("cpufreq: imx: Add support for 700MHz setpoint in
cpufreq") in downstream is doing, it avoids changing pll twice though.

And, as mentioned in the commit log, the dc_reg part is missing. This is
because it is not required on our Colibri iMX6ULL since it uses a higher
(not switchable) VDD_SOC_IN voltage by default.

--
Stefan

>> ---
>>  drivers/cpufreq/imx6q-cpufreq.c | 14 ++++++++------
>>  1 file changed, 8 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/cpufreq/imx6q-cpufreq.c b/drivers/cpufreq/imx6q-cpufreq.c
>> index 628fe899cb48..840f6386c780 100644
>> --- a/drivers/cpufreq/imx6q-cpufreq.c
>> +++ b/drivers/cpufreq/imx6q-cpufreq.c
>> @@ -114,12 +114,14 @@ static int imx6q_set_target(struct cpufreq_policy *policy, unsigned int index)
>>  		 */
>>  		clk_set_rate(arm_clk, (old_freq >> 1) * 1000);
>>  		clk_set_parent(pll1_sw_clk, pll1_sys_clk);
>> -		if (freq_hz > clk_get_rate(pll2_pfd2_396m_clk))
>> -			clk_set_parent(secondary_sel_clk, pll2_bus_clk);
>> -		else
>> -			clk_set_parent(secondary_sel_clk, pll2_pfd2_396m_clk);
>> -		clk_set_parent(step_clk, secondary_sel_clk);
>> -		clk_set_parent(pll1_sw_clk, step_clk);
>> +		if (freq_hz <= clk_get_rate(pll2_bus_clk)) {
>> +			if (freq_hz > clk_get_rate(pll2_pfd2_396m_clk))
>> +				clk_set_parent(secondary_sel_clk, pll2_bus_clk);
>> +			else
>> +				clk_set_parent(secondary_sel_clk, pll2_pfd2_396m_clk);
>> +			clk_set_parent(step_clk, secondary_sel_clk);
>> +			clk_set_parent(pll1_sw_clk, step_clk);
>> +		}
>>  	} else {
>>  		clk_set_parent(step_clk, pll2_pfd2_396m_clk);
>>  		clk_set_parent(pll1_sw_clk, step_clk);
>>