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

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Date:   Fri, 28 Jul 2017 10:36:33 +0200
From:   Sébastien Szymanski 
        <sebastien.szymanski@...adeus.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-arm-kernel@...ts.infradead.org, linux-pm@...r.kernel.org,
        Viresh Kumar <viresh.kumar@...aro.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Shawn Guo <shawnguo@...nel.org>,
        Fabio Estevam <fabio.estevam@....com>,
        Julien Boibessot <julien.boibessot@...adeus.com>,
        Sébastien Szymanski 
        <sebastien.szymanski@...adeus.com>
Subject: [PATCH 1/1] cpufreq: imx6q: imx6ull: use PLL1 for frequency higher than 528MHz

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);
-- 
2.7.3