linux-kernel - Re: [PATCH v3 1/4] ARM: EXYNOS: fix CPU1 hotplug for AFTR mode on Exynos3250

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Date:	Wed, 18 Mar 2015 14:23:35 +0100
From:	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
To:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
Cc:	Kukjin Kim <kgene.kim@...sung.com>, Kukjin Kim <kgene@...nel.org>,
	linux-samsung-soc@...r.kernel.org, linux-pm@...r.kernel.org,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Tomasz Figa <tomasz.figa@...il.com>,
	linux-kernel@...r.kernel.org, Chanwoo Choi <cw00.choi@...sung.com>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 1/4] ARM: EXYNOS: fix CPU1 hotplug for AFTR mode on
 Exynos3250


Hi,

On Wednesday, March 18, 2015 02:10:31 PM Krzysztof Kozlowski wrote:
> 2015-03-18 13:51 GMT+01:00 Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>:
> > CPU1 hotplug may hang when AFTR is used.  Fix it by:
> > - setting AUTOWAKEUP_EN bit in ARM_COREx_CONFIGURATION register in
> >   exynos_cpu_power_up()
> > - not clearing reserved bits of ARM_COREx_CONFIGURATION register in
> >   exynos_cpu_power_down()
> > - waiting while an undocumented register 0x0908 becomes non-zero in
> >   exynos_core_restart()
> > - using dsb_sev() instead of IPI in exynos_boot_secondary() on
> >   Exynos3250
> >
> > Cc: Daniel Lezcano <daniel.lezcano@...aro.org>
> > Signed-off-by: Chanwoo Choi <cw00.choi@...sung.com>
> > Signed-off-by: Krzysztof Kozlowski <k.kozlowski@...sung.com>
> > Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
> > Acked-by: Kyungmin Park <kyungmin.park@...sung.com>
> > ---
> >  arch/arm/mach-exynos/platsmp.c  | 23 ++++++++++++++++++++---
> >  arch/arm/mach-exynos/regs-pmu.h |  2 ++
> >  2 files changed, 22 insertions(+), 3 deletions(-)
> 
> 
> Looks good (except one nit below) and this also fixes hotplug issues
> during resume from S2R:
> $ echo mem > /sys/power/state
> [  156.517266] Disabling non-boot CPUs ...
> [  156.517781] IRQ18 no longer affine to CPU1
> [  156.518043] CPU1: shutdown
> [  156.544718] Enabling non-boot CPUs ...
> [  156.554925] CPU1: Software reset
> [  158.552631] CPU1: failed to come online
> [  158.552753] Error taking CPU1 up: -5
> 
> Reviewed and tested on Rinato (Gear 2/Exynos 3250) board:
> 
> Reviewed-by: Krzysztof Kozlowski <k.kozlowski@...sung.com>
> Tested-by: Krzysztof Kozlowski <k.kozlowski@...sung.com>

Thank you!

> One comment below...
> 
> >
> > diff --git a/arch/arm/mach-exynos/platsmp.c b/arch/arm/mach-exynos/platsmp.c
> > index d2e9f12..ebd135b 100644
> > --- a/arch/arm/mach-exynos/platsmp.c
> > +++ b/arch/arm/mach-exynos/platsmp.c
> > @@ -126,6 +126,8 @@ static inline void platform_do_lowpower(unsigned int cpu, int *spurious)
> >   */
> >  void exynos_cpu_power_down(int cpu)
> >  {
> > +       u32 core_conf;
> > +
> >         if (cpu == 0 && (soc_is_exynos5420() || soc_is_exynos5800())) {
> >                 /*
> >                  * Bypass power down for CPU0 during suspend. Check for
> > @@ -137,7 +139,10 @@ void exynos_cpu_power_down(int cpu)
> >                 if (!(val & S5P_CORE_LOCAL_PWR_EN))
> >                         return;
> >         }
> > -       pmu_raw_writel(0, EXYNOS_ARM_CORE_CONFIGURATION(cpu));
> > +
> > +       core_conf = pmu_raw_readl(EXYNOS_ARM_CORE_CONFIGURATION(cpu));
> > +       core_conf &= ~S5P_CORE_LOCAL_PWR_EN;
> > +       pmu_raw_writel(core_conf, EXYNOS_ARM_CORE_CONFIGURATION(cpu));
> >  }
> >
> >  /**
> > @@ -148,7 +153,12 @@ void exynos_cpu_power_down(int cpu)
> >   */
> >  void exynos_cpu_power_up(int cpu)
> >  {
> > -       pmu_raw_writel(S5P_CORE_LOCAL_PWR_EN,
> > +       u32 core_conf = S5P_CORE_LOCAL_PWR_EN;
> > +
> > +       if (soc_is_exynos3250())
> > +               core_conf |= S5P_CORE_AUTOWAKEUP_EN;
> > +
> > +       pmu_raw_writel(core_conf,
> >                         EXYNOS_ARM_CORE_CONFIGURATION(cpu));
> >  }
> >
> > @@ -226,6 +236,10 @@ static void exynos_core_restart(u32 core_id)
> >         if (!of_machine_is_compatible("samsung,exynos3250"))
> >                 return;
> >
> > +       while (!pmu_raw_readl(S5P_PMU_SPARE2))
> > +               udelay(10);
> > +       udelay(10);
> 
> We really need to start documenting this. Please add short description
> why this SPARE2 check is here and who uses it. Without documenting
> this behavior future generations won't be able to debug this stuff.
> Imagine replacing sboot with uboot by someone...

I've already planned to do this for this code and for coupled cpuidle
use of SPARE2 as well.  However I would really prefer to do it in
an incremental patch if there are no other issues with this patchset.

Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics

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