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

From: Stefan Agner
Date: Sun Feb 11 2018 - 11:17:51 EST


On 11.02.2018 02:42, Anson Huang wrote:
> Anson Huang
> Best Regards!
>
>
>> -----Original Message-----
>> From: Fabio Estevam [mailto:festevam@xxxxxxxxx]
>> Sent: Sunday, February 11, 2018 12:26 AM
>> To: Stefan Agner <stefan@xxxxxxxx>; Anson Huang <anson.huang@xxxxxxx>
>> Cc: rjw@xxxxxxxxxxxxx; viresh kumar <viresh.kumar@xxxxxxxxxx>;
>> linux-pm@xxxxxxxxxxxxxxx; Marcel Ziswiler <marcel.ziswiler@xxxxxxxxxxx>;
>> max.oss.09@xxxxxxxxx; linux-kernel <linux-kernel@xxxxxxxxxxxxxxx>; Octavian
>> Purdila <octavian.purdila@xxxxxxx>; Fabio Estevam
>> <fabio.estevam@xxxxxxx>; Shawn Guo <shawnguo@xxxxxxxxxx>; moderated
>> list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE
>> <linux-arm-kernel@xxxxxxxxxxxxxxxxxxx>; dl-linux-imx <linux-imx@xxxxxxx>
>> Subject: Re: [PATCH] cpufreq: imx6q: support frequencies >528MHz for
>> i.MX6UL/ULL
>>
>> Hi Anson,
>>
>> On Thu, Jan 18, 2018 at 9:58 PM, Stefan Agner <stefan@xxxxxxxx> 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@xxxxxxxx>
>> > ---
>> > 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);
>> > + }
>
> For cpufreq > 528MHz, ARM PLL needs to be set_rate, I did NOT see
> where sets ARM PLL rate?

This is done unconditionally after the if statement:

if (of_machine_is_compatible("fsl,imx6ul") ||
of_machine_is_compatible("fsl,imx6ull")) {
/*
* When changing pll1_sw_clk's parent to pll1_sys_clk,
* CPU may run at higher than 528MHz, this will lead to
* the system unstable if the voltage is lower than the
* 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 (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);
if (freq_hz > clk_get_rate(pll2_pfd2_396m_clk)) {
clk_set_rate(pll1_sys_clk, new_freq * 1000);
clk_set_parent(pll1_sw_clk, pll1_sys_clk);
} else {
/* pll1_sys needs to be enabled for divider rate change to work. */
pll1_sys_temp_enabled = true;
clk_prepare_enable(pll1_sys_clk);
}
}

/* Ensure the arm clock divider is what we expect */
ret = clk_set_rate(arm_clk, new_freq * 1000);


--
Stefan



>
> Anson.
>
>> > } else {
>> > clk_set_parent(step_clk, pll2_pfd2_396m_clk);
>> > clk_set_parent(pll1_sw_clk, step_clk);
>>
>> Could you please help reviewing this patch?
>>
>> Thanks