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

[Anson Huang]

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