[PATCH v3 0/3] MCPM/TC2 support for CPU powerdown synchronisation

Thu Oct 24 08:48:13 EDT 2013

Hi Dave Martin,

   With the below configuration, I tried to check cpu hotplug as this
is prerequisite for kexec.
I see cpu hotplug fails. hot-unplug is OK but hot plug-in fails.

Below is my DCC board configuration

SCC REGISTERS]
TOTALSCCS: 32                   ;Total Number of SCC registers
SCC: 0x018 0x1FFFFFFF
SCC: 0x01C 0xFF00FF00           ;CFGRW3  - SMC CS6/7 N/U
SCC: 0x118 0x01CD1011           ;CFGRW17 - HDLCD PLL external bypass
;SCC: 0x700 0x1032F003           ;CFGRW48 - [25:24]Boot CPU [28]Boot
Cluster (default CA7_0)
SCC: 0x700 0x0032D003           ;CFGRW48 - [25:24]Boot CPU [28]Boot
Cluster (default CA7_0)
                                ;          Bootmon configuration:
                                ;          [15]: A7 Event stream
generation (default: disabled)
                                ;          [14]: A15 Event stream
generation (default: disabled)
                                ;          [13]: Power down the
non-boot cluster (default: disabled)
                                ;          [12]: Use per-cpu mailboxes
for power management (default: disabled)
                                ;          [11]: A15 executes WFEs as
nops (default: disabled)
                                ;          [ 4]: Erase UEFI variable
storage in NOR flash

SCC: 0x400 0x33330c00           ;CFGREG41 - A15 configuration register
0 (Default 0x33330c80)
                                ;       [29:28] SPNIDEN
                                ;       [25:24] SPIDEN
                                ;       [21:20] NIDEN
                                ;       [17:16] DBGEN
                                ;       [13:12] CFGTE
                                ;       [9:8] VINITHI_CORE
                                ;       [7] IMINLN
                                ;       [3:0] CLUSTER_ID

;Power management interface

SCC: 0xC00 0x00000005           ;Control: [0]PMI_EN [1]DBG_EN [2]SPC_SYSCFG
SCC: 0xC04 0x000005DC           ;Latency in uS max: [15:0]DVFS [31:16]PWRUP

On Mon, Oct 21, 2013 at 6:47 PM, Vijay Kilari <vijay.kilari at gmail.com> wrote:
> Hi Dave Martin,
>
>   On which kernel base this kexec is tested? is it 3.10 or 3.12?
> can you please share your git (public) if available?
>
> I tested using 3.10 + TC2 patches. However I see sometimes kexec fails
> to reboot and hangs at very early stage (log below)
>
> root at armeb-cortex-a15:/# kexec -e
> [   59.311559] Starting new kernel
>
> Thanks
> Vijay
>
> Message: 2
> Date: Tue,  1 Oct 2013 18:15:15 +0100
> From: Dave Martin <Dave.Martin at arm.com>
> To: linux-arm-kernel at lists.infradead.org
> Cc: Nicolas Pitre <nicolas.pitre at linaro.org>, Lorenzo Pieralisi
>         <Lorenzo.Pieralisi at arm.com>, Pawel Moll <Pawel.Moll at arm.com>, Sudeep
>         KarkadaNagesha <Sudeep.KarkadaNagesha at arm.com
>>, Will Deacon
>         <Will.Deacon at arm.com>, Dave Martin <Dave.Martin at arm.com>
> Subject: [PATCH v3 0/3] MCPM/TC2 support for CPU powerdown
>         synchronisation
> Message-ID: <1380647718-9178-1-git-send-email-Dave.Martin at arm.com>
>
> This series adds MCPM support for detecting when a CPU is safely powered
> down, and provides an implementation for TC2.
>
> It should be possible to implement the same thing for PSCI using the
> AFFINITY_INFO call (I need to check the semantics with Charles)
>
> This is sufficient to for working kexec with real power management on
> TC2.  To test it, you'll also need:
>
>   * CONFIG_KEXEC=y
>   * CONFIG_PROC_DEVICE_TREE=y
>   * CONFIG_MCPM=y
>   * CONFIG_ARCH_VEXPRESS_TC2_PM=y
>   * sufficiently new kexec-tools
>     (git://git.kernel.org/pub/scm/utils/kernel/kexec/kexec-tools.git
>     v2.0.4 worked for me)
>
> This build on Nico's patch
> http://www.arm.linux.org.uk/developer/patches/viewpatch.php?id=7842/1
> (MCPM: don't explode if invoked without being initialized first)
>
> To prevent CPUs from running off into the weeds across kexec, this
> series requires Lorenzo's patch
> http://lists.infradead.org/pipermail/linux-arm-kernel/2013-September/200917.html
> (arm: vexpress: tc2: fix hotplug/idle/kexec race on cluster power down).
>
> Changes since v2:
>
>  * Return a proper failure code if mcpm_cpu_power_down_finish() is
>    called with no mcpm platforms_ops registered, or a NULL
>    power_down_finish() method.  (Thanks again Nico)
>
>  * Minor refactoring of the loop in tc2_pm_power_down_finish() to
>    avoid the goto.
>
> Changes between v1 and v2:
>
>  * "Fix" erroneous documentation comment by switching to -errno return
>    value convention for power_down_finish(), which is more informative.
>    tc2_pm now returns -ETIMEDOUT on timeout.  The return is adapted to
>    bool convention on return from smp_ops.cpu_kill() instead.  (Thanks,
>    Nico).
>
>  * For consistency, BUG_ON out of range cpu or cluster values
>    tc2_pm_power_down_finish(), as for tc2_pm_power_down().
>
> Changes between RFC and v1:
>
>  * Print a big fat warning instead of branching to null if the
>    power_down_finish() method is not supplied by the backend, or not
>    registered.
>
>  * Add a generous timeout of 1 second for the TC2 implementation.
>
>  * Relax the polling interval to 10ms for TC2, since the need to poll
>    more than once is rare and this is not a performance-critical path.
>
>  * Fix some silly typos.
>
>
> Dave Martin (3):
>   ARM: mcpm: Factor out logical-to-physical CPU translation
>   ARM: mcpm: Implement cpu_kill() to synchronise on powerdown
>   ARM: vexpress/TC2: Implement MCPM power_down_finish()
>
>  arch/arm/common/mcpm_entry.c    |   15 +++++++++
>  arch/arm/common/mcpm_platsmp.c  |   27 +++++++++++++---
>  arch/arm/include/asm/mcpm.h     |   31 ++++++++++++++++++
>  arch/arm/mach-vexpress/spc.c    |   39 +++++++++++++++++++++++
>  arch/arm/mach-vexpress/spc.h    |    1 +
>  arch/arm/mach-vexpress/tc2_pm.c |   66 ++++++++++++++++++++++++++++++++++++---
>  6 files changed, 170 insertions(+), 9 deletions(-)
>
> --
> 1.7.9.5