[PATCH 1/3] ARM: EXYNOS: remove non-working AFTR mode support
Bartlomiej Zolnierkiewicz
b.zolnierkie at samsung.com
Thu Jun 27 14:10:53 EDT 2013
On Wednesday, June 26, 2013 12:36:12 PM Daniel Lezcano wrote:
> On 06/26/2013 12:13 PM, Bartlomiej Zolnierkiewicz wrote:
> > AFTR mode support was introduced by commit 67173ca ("ARM: EXYNOS: Add
> > support AFTR mode on EXYNOS4210") in v3.4 kernel. Unfortunately even
> > in v3.4 kernel it hasn't worked as supposed and this is still the case
> > with v3.10-rc6 (it probably wasn't noticed because CONFIG_CPU_IDLE is
> > not turned on by default):
> >
> > - on revision 0 of Exynos4210 (Universal C210 board) it causes lockup
> > (on this revision only one core is usable so entry to AFTR mode is
> > always attempted because the code tries to go into AFTR mode when all
> > other CPUs except CPU0 are offlined)
> >
> > - on revision 1.1 of Exynos4210 (Trats board) it causes a lockup when
> > CPU1 is offlined (i.e. echo 0 > /sys/devices/system/cpu/cpu1/online)
> >
> > - on later Exynos4/5 SoCs wrong registers may be accessed when all CPUs
> > except CPU0 are offlined resulting in panic/lockup (REG_DIRECTGO_ADDR
> > and REG_DIRECTGO_FLAG register selections was implemented only for
> > Exynos4210)
> >
> > Just remove AFTR mode support for now.
>
> Ok, I will jump on the opportunity to talk about this state.
>
> 1. I tried different ways to make the AFTR state to be entered with
> *both* cpu online. It goes successfully to this state. The CPU0 is
> correctly woken up but the CPU1 is never woken up, why is it happening ?
>
> https://bugs.launchpad.net/linaro-landing-team-samsung/+bug/1171518
No idea here, AFTR doesn't work for me with upstream kernels even if
only one CPU is online.
Also the documentation says that before entering system-level power-down
mode (such as AFTR) when multiple CPUs cores are used all other CPU cores
should stop interrupt service so I'm not sure how the way attempted by
you should work.
> 2. The CPU1 hotplug bug should been fixed and if I am not wrong there is
> a patch somewhere fixing this.
>
> https://bugs.launchpad.net/linaro-power-kernel/+bug/1171382
Unfortunately none of the patches there helps with my issues.
> 3. What is the fix for Exynos5 ?
>
> https://bugs.launchpad.net/linaro-power-kernel/+bug/1171253
>
> It sounds like depending on Hypervisor mode is enabled or not, the AFTR
> does not work correctly.
Sorry no idea here either. On any SoCs later than EXYNOS4210 the
registers used for s3c_cpu_resume address and 0xFCBA0D10 magic number
may be different than EXYNOS4210 defaults (at least on EXYNOS4412 they
indeed are different, unfortunately I lack any info needed for EXYNOS5
support). You are lucky that it even works in some cases on EXYNOS5250.
> In other words, instead of removing the AFTR state I suggest to fix it:
> both core being online, split driver for exynos4 and 5.
My main problem is that with the upstream kernel even on EXYNOS4210
rev0 (only one core useable due to hardware issues) the kernel goes
into AFTR state for the first few times during boot and then it just
lockups (after going into cpu_do_idle() which is really cpu_v7_do_idle()
and which does wfi call) and doesn't wake up CPU0. I have currently
no idea how to fix or debug it further.
The issue happens with every upstream kernel version tried (from v3.4
to v3.10-rc6). Lockups also happen on EXYNOS4210 rev1.1 when CPU1 is
offlined by hand and then cpuidle driver tries to go into AFTR mode
(because by default it doesn't go into AFTR mode on any SoC except
EXYNOS4210 rev0).
I don't have EXYNOS4210 rev1.0 but it seems that in the upstream AFTR
mode has never worked (even on hardware that it was originally developed
on) since its introduction in v3.4 (which was released on 20th May 2012).
IOW for over the year nobody cared to make it work and I have currently
no fix at hand so the corrent upstream resolution is to just remove the
known non-working code and re-introduce it later when/if needed (I can
just disable it with a small fix but we don't keep such long-term broken
code as placeholder in the upstream kernel). If left as it is people
can hit the known issues and waste time debugging them, just like this
happenend for me [1].
If you have AFTR mode working (especially on EXYNOS4210) in Linaro
kernels please get fixes upstream ASAP. However I still wonder whether
the maintanance nightmare (bugs for different cases in your launchpad)
is worth gains over standard idle mode as the rumor around here is that
they are not that great (unfortunately no numbers were provided during
original feature addition).
Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics
[1] Somebody enabled CONFIG_CPU_IDLE in the default config in one of our
internal kernel trees on a target on which this feature "works" (since
CPUs are not hot-unplugged by default on all targets except EXYNOS4210
rev0 the code for AFTR is not used) and resulted in lockups on boot on
my default testing target. It took my long time to find out that problem
is actually caused by just enabling exynos cpuidle driver.
> Thanks
> -- Daniel
>
> > Cc: Jaecheol Lee <jc.lee at samsung.com>
> > Cc: Lorenzo Pieralisi <lorenzo.pieralisi at arm.com>
> > Cc: Amit Daniel Kachhap <amit.kachhap at linaro.org>
> > Cc: Tomasz Figa <t.figa at samsung.com>
> > Cc: Kukjin Kim <kgene.kim at samsung.com>
> > Cc: Daniel Lezcano <daniel.lezcano at linaro.org>
> > Cc: "Rafael J. Wysocki" <rjw at sisk.pl>
> > Signed-off-by: Kyungmin Park <kyungmin.park at samsung.com>
> > Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie at samsung.com>
> > ---
> > arch/arm/mach-exynos/cpuidle.c | 131 +----------------------------------------
> > 1 file changed, 1 insertion(+), 130 deletions(-)
> >
> > diff --git a/arch/arm/mach-exynos/cpuidle.c b/arch/arm/mach-exynos/cpuidle.c
> > index 17a18ff..0a657ac 100644
> > --- a/arch/arm/mach-exynos/cpuidle.c
> > +++ b/arch/arm/mach-exynos/cpuidle.c
> > @@ -17,30 +17,11 @@
> > #include <linux/time.h>
> >
> > #include <asm/proc-fns.h>
> > -#include <asm/smp_scu.h>
> > -#include <asm/suspend.h>
> > -#include <asm/unified.h>
> > #include <asm/cpuidle.h>
> > #include <mach/regs-clock.h>
> > -#include <mach/regs-pmu.h>
> > -
> > -#include <plat/cpu.h>
> >
> > #include "common.h"
> >
> > -#define REG_DIRECTGO_ADDR (samsung_rev() == EXYNOS4210_REV_1_1 ? \
> > - S5P_INFORM7 : (samsung_rev() == EXYNOS4210_REV_1_0 ? \
> > - (S5P_VA_SYSRAM + 0x24) : S5P_INFORM0))
> > -#define REG_DIRECTGO_FLAG (samsung_rev() == EXYNOS4210_REV_1_1 ? \
> > - S5P_INFORM6 : (samsung_rev() == EXYNOS4210_REV_1_0 ? \
> > - (S5P_VA_SYSRAM + 0x20) : S5P_INFORM1))
> > -
> > -#define S5P_CHECK_AFTR 0xFCBA0D10
> > -
> > -static int exynos4_enter_lowpower(struct cpuidle_device *dev,
> > - struct cpuidle_driver *drv,
> > - int index);
> > -
> > static DEFINE_PER_CPU(struct cpuidle_device, exynos4_cpuidle_device);
> >
> > static struct cpuidle_driver exynos4_idle_driver = {
> > @@ -48,117 +29,11 @@ static struct cpuidle_driver exynos4_idle_driver = {
> > .owner = THIS_MODULE,
> > .states = {
> > [0] = ARM_CPUIDLE_WFI_STATE,
> > - [1] = {
> > - .enter = exynos4_enter_lowpower,
> > - .exit_latency = 300,
> > - .target_residency = 100000,
> > - .flags = CPUIDLE_FLAG_TIME_VALID,
> > - .name = "C1",
> > - .desc = "ARM power down",
> > - },
> > },
> > - .state_count = 2,
> > + .state_count = 1,
> > .safe_state_index = 0,
> > };
> >
> > -/* Ext-GIC nIRQ/nFIQ is the only wakeup source in AFTR */
> > -static void exynos4_set_wakeupmask(void)
> > -{
> > - __raw_writel(0x0000ff3e, S5P_WAKEUP_MASK);
> > -}
> > -
> > -static unsigned int g_pwr_ctrl, g_diag_reg;
> > -
> > -static void save_cpu_arch_register(void)
> > -{
> > - /*read power control register*/
> > - asm("mrc p15, 0, %0, c15, c0, 0" : "=r"(g_pwr_ctrl) : : "cc");
> > - /*read diagnostic register*/
> > - asm("mrc p15, 0, %0, c15, c0, 1" : "=r"(g_diag_reg) : : "cc");
> > - return;
> > -}
> > -
> > -static void restore_cpu_arch_register(void)
> > -{
> > - /*write power control register*/
> > - asm("mcr p15, 0, %0, c15, c0, 0" : : "r"(g_pwr_ctrl) : "cc");
> > - /*write diagnostic register*/
> > - asm("mcr p15, 0, %0, c15, c0, 1" : : "r"(g_diag_reg) : "cc");
> > - return;
> > -}
> > -
> > -static int idle_finisher(unsigned long flags)
> > -{
> > - cpu_do_idle();
> > - return 1;
> > -}
> > -
> > -static int exynos4_enter_core0_aftr(struct cpuidle_device *dev,
> > - struct cpuidle_driver *drv,
> > - int index)
> > -{
> > - unsigned long tmp;
> > -
> > - exynos4_set_wakeupmask();
> > -
> > - /* Set value of power down register for aftr mode */
> > - exynos_sys_powerdown_conf(SYS_AFTR);
> > -
> > - __raw_writel(virt_to_phys(s3c_cpu_resume), REG_DIRECTGO_ADDR);
> > - __raw_writel(S5P_CHECK_AFTR, REG_DIRECTGO_FLAG);
> > -
> > - save_cpu_arch_register();
> > -
> > - /* Setting Central Sequence Register for power down mode */
> > - tmp = __raw_readl(S5P_CENTRAL_SEQ_CONFIGURATION);
> > - tmp &= ~S5P_CENTRAL_LOWPWR_CFG;
> > - __raw_writel(tmp, S5P_CENTRAL_SEQ_CONFIGURATION);
> > -
> > - cpu_pm_enter();
> > - cpu_suspend(0, idle_finisher);
> > -
> > -#ifdef CONFIG_SMP
> > - if (!soc_is_exynos5250())
> > - scu_enable(S5P_VA_SCU);
> > -#endif
> > - cpu_pm_exit();
> > -
> > - restore_cpu_arch_register();
> > -
> > - /*
> > - * If PMU failed while entering sleep mode, WFI will be
> > - * ignored by PMU and then exiting cpu_do_idle().
> > - * S5P_CENTRAL_LOWPWR_CFG bit will not be set automatically
> > - * in this situation.
> > - */
> > - tmp = __raw_readl(S5P_CENTRAL_SEQ_CONFIGURATION);
> > - if (!(tmp & S5P_CENTRAL_LOWPWR_CFG)) {
> > - tmp |= S5P_CENTRAL_LOWPWR_CFG;
> > - __raw_writel(tmp, S5P_CENTRAL_SEQ_CONFIGURATION);
> > - }
> > -
> > - /* Clear wakeup state register */
> > - __raw_writel(0x0, S5P_WAKEUP_STAT);
> > -
> > - return index;
> > -}
> > -
> > -static int exynos4_enter_lowpower(struct cpuidle_device *dev,
> > - struct cpuidle_driver *drv,
> > - int index)
> > -{
> > - int new_index = index;
> > -
> > - /* This mode only can be entered when other core's are offline */
> > - if (num_online_cpus() > 1)
> > - new_index = drv->safe_state_index;
> > -
> > - if (new_index == 0)
> > - return arm_cpuidle_simple_enter(dev, drv, new_index);
> > - else
> > - return exynos4_enter_core0_aftr(dev, drv, new_index);
> > -}
> > -
> > static void __init exynos5_core_down_clk(void)
> > {
> > unsigned int tmp;
> > @@ -209,10 +84,6 @@ static int __init exynos4_init_cpuidle(void)
> > device = &per_cpu(exynos4_cpuidle_device, cpu_id);
> > device->cpu = cpu_id;
> >
> > - /* Support IDLE only */
> > - if (cpu_id != 0)
> > - device->state_count = 1;
> > -
> > ret = cpuidle_register_device(device);
> > if (ret) {
> > printk(KERN_ERR "CPUidle register device failed\n");
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