linux-kernel - RE: [PATCH] ARM: imx: add cpuidle support for i.mx6ul

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Date:   Fri, 26 Aug 2016 03:33:58 +0000
From:   Yongcai Huang <anson.huang@....com>
To:     Peter Chen <hzpeterchen@...il.com>
CC:     "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Fabio Estevam <fabio.estevam@....com>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "linux@...linux.org.uk" <linux@...linux.org.uk>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>
Subject: RE: [PATCH] ARM: imx: add cpuidle support for i.mx6ul

Best Regards!
Anson Huang

> -----Original Message-----
> From: Peter Chen [mailto:hzpeterchen@...il.com]
> Sent: 2016-08-25 3:09 PM
> To: Yongcai Huang <anson.huang@....com>
> Cc: linux-arm-kernel@...ts.infradead.org; lkml <linux-kernel@...r.kernel.org>;
> Fabio Estevam <fabio.estevam@....com>; shawnguo@...nel.org;
> linux@...linux.org.uk; kernel@...gutronix.de
> Subject: Re: [PATCH] ARM: imx: add cpuidle support for i.mx6ul
> 
> >
> > Signed-off-by: Anson Huang <Anson.Huang@....com>
> > ---
> >  arch/arm/mach-imx/cpuidle-imx6sx.c | 10 ++++++++++
> >  arch/arm/mach-imx/mach-imx6ul.c    |  3 +++
> >  2 files changed, 13 insertions(+)
> >
> > diff --git a/arch/arm/mach-imx/cpuidle-imx6sx.c
> > b/arch/arm/mach-imx/cpuidle-imx6sx.c
> > index 41cdce6..b4fcc8ae 100644
> > --- a/arch/arm/mach-imx/cpuidle-imx6sx.c
> > +++ b/arch/arm/mach-imx/cpuidle-imx6sx.c
> > @@ -9,14 +9,21 @@
> >  #include <linux/cpuidle.h>
> >  #include <linux/cpu_pm.h>
> >  #include <linux/module.h>
> > +#include <linux/of.h>
> > +#include <asm/cacheflush.h>
> >  #include <asm/cpuidle.h>
> >  #include <asm/suspend.h>
> >
> >  #include "common.h"
> >  #include "cpuidle.h"
> >
> > +static bool pl310_available;
> > +
> 
> 
> >  static int imx6sx_idle_finish(unsigned long val)  {
> > +       /* check if need to flush internal L2 cache */
> > +       if (!pl310_available)
> 
> Just wondering why you need an extra variable here?
> Calling of_find_compatible_node takes long time at that time?
> 
> Peter
> 

Because cpu idle enter/exit is called very frequently, so calling
of_find_compatible_node in every cpu idle thread is adding too
many latency, I think adding a variable is better.

Anson

> > +               flush_cache_all();
> >         cpu_do_idle();
> >
> >         return 0;
> > @@ -101,5 +108,8 @@ int __init imx6sx_cpuidle_init(void)
> >         imx_gpc_set_arm_power_up_timing(2, 1);
> >         imx_gpc_set_arm_power_down_timing(1, 1);
> >
> > +       if (of_find_compatible_node(NULL, NULL, "arm,pl310-cache"))
> > +               pl310_available = true;
> > +
> >         return cpuidle_register(&imx6sx_cpuidle_driver, NULL);  } diff
> > --git a/arch/arm/mach-imx/mach-imx6ul.c
> > b/arch/arm/mach-imx/mach-imx6ul.c index c2cd61c..9c5e8f3 100644
> > --- a/arch/arm/mach-imx/mach-imx6ul.c
> > +++ b/arch/arm/mach-imx/mach-imx6ul.c
> > @@ -16,6 +16,7 @@
> >  #include <asm/mach/map.h>
> >
> >  #include "common.h"
> > +#include "cpuidle.h"
> >
> >  static void __init imx6ul_enet_clk_init(void)  { @@ -80,6 +81,8 @@
> > static void __init imx6ul_init_irq(void)
> >
> >  static void __init imx6ul_init_late(void)  {
> > +       imx6sx_cpuidle_init();
> > +
> >         if (IS_ENABLED(CONFIG_ARM_IMX6Q_CPUFREQ)) {
> >                 imx6_pm_opp_init();
> >                 platform_device_register_simple("imx6q-cpufreq", -1,
> > NULL, 0);
> > --
> > 1.9.1
> >
> >
> > _______________________________________________
> > linux-arm-kernel mailing list
> > linux-arm-kernel@...ts.infradead.org
> > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

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