linux-kernel - Re: [PATCH 1/1] cpufreq: imx6q: imx6ull: use PLL1 for frequency higher than 528MHz

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Message-ID: <1790312.mdBOOMI6jx@aspire.rjw.lan>
Date:   Wed, 02 Aug 2017 01:25:14 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Sébastien Szymanski 
        <sebastien.szymanski@...adeus.com>,
        linux-arm-kernel@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Shawn Guo <shawnguo@...nel.org>,
        Fabio Estevam <fabio.estevam@....com>,
        Julien Boibessot <julien.boibessot@...adeus.com>
Subject: Re: [PATCH 1/1] cpufreq: imx6q: imx6ull: use PLL1 for frequency higher than 528MHz

On Friday, July 28, 2017 10:36:33 AM Sébastien Szymanski wrote:
> Setting the frequency higher than 528Mhz actually sets the ARM
> clock to 528MHz. That's because PLL2 is used as the root clock when the
> frequency is higher than 396MHz.
> 
> cpupower frequency-set -f 792000
> 
> arm_clk_root on the CCM_CLKO2 signal is 528MHz instead of 792MHz.
> 
> [   61.606383] cpu cpu0: 396 MHz, 1025 mV --> 792 MHz, 1225 mV
> 
> pll2                         1  1  528000000 0 0
>    pll2_bypass               1  1  528000000 0 0
>       pll2_bus               3  3  528000000 0 0
> 	 ca7_secondary_sel   1  1  528000000 0 0
> 	    step             1  1  528000000 0 0
> 	       pll1_sw       1  1  528000000 0 0
> 		  arm        1  1  528000000 0 0
> 
> Fixes this by using the PLL1 as the root clock when the frequency is
> higher than 528MHz.
> 
> cpupower frequency-set -f 792000
> 
> arm_clk_root on the CCM_CLKO2 signal is now 792MHz as expected.
> 
> [   69.717987] cpu cpu0: 198 MHz, 950 mV --> 792 MHz, 1225 mV
> 
> pll1               1 1 792000000 0 0
>    pll1_bypass     1 1 792000000 0 0
>       pll1_sys     1 1 792000000 0 0
> 	 pll1_sw   1 1 792000000 0 0
> 	    arm    1 1 792000000 0 0
> 
> Signed-off-by: Sébastien Szymanski <sebastien.szymanski@...adeus.com>
> ---
>  drivers/cpufreq/imx6q-cpufreq.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/cpufreq/imx6q-cpufreq.c b/drivers/cpufreq/imx6q-cpufreq.c
> index b6edd3c..e5fba50 100644
> --- a/drivers/cpufreq/imx6q-cpufreq.c
> +++ b/drivers/cpufreq/imx6q-cpufreq.c
> @@ -18,6 +18,7 @@
>  
>  #define PU_SOC_VOLTAGE_NORMAL	1250000
>  #define PU_SOC_VOLTAGE_HIGH	1275000
> +#define FREQ_528_MHZ		528000000
>  #define FREQ_1P2_GHZ		1200000000
>  
>  static struct regulator *arm_reg;
> @@ -110,14 +111,20 @@ static int imx6q_set_target(struct cpufreq_policy *policy, unsigned int index)
>  		 * voltage of 528MHz, so lower the CPU frequency to one
>  		 * half before changing CPU frequency.
>  		 */
> -		clk_set_rate(arm_clk, (old_freq >> 1) * 1000);
> -		clk_set_parent(pll1_sw_clk, pll1_sys_clk);
> +		if ((old_freq * 1000) <= FREQ_528_MHZ) {
> +			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 > FREQ_528_MHZ) {
> +			clk_set_rate(pll1_sys_clk, freq_hz);
> +			clk_set_parent(pll1_sw_clk, pll1_sys_clk);
> +		}
>  	} else {
>  		clk_set_parent(step_clk, pll2_pfd2_396m_clk);
>  		clk_set_parent(pll1_sw_clk, step_clk);
> 

Any comments anyone?  Good, bad, ugly?