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

From: Anson Huang
Date: Mon Feb 12 2018 - 02:25:04 EST




Anson Huang
Best Regards!


> -----Original Message-----
> From: Stefan Agner [mailto:stefan@xxxxxxxx]
> Sent: Monday, February 12, 2018 12:18 AM
> To: Anson Huang <anson.huang@xxxxxxx>
> Cc: Fabio Estevam <festevam@xxxxxxxxx>; 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
>
> 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

Thanks, I see the CLK_SET_RATE_PARENT flag is set for arm clk.

Reviewed-by: Anson Huang <Anson.Huang@xxxxxxx>

Anson.
>
>
>
> >
> > 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