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Message-ID: <CANuQgHHbDze0VthjnnKm8R3gny=4ubPUjr2jnkGnh7a-OK2siQ@mail.gmail.com>
Date: Wed, 19 Jun 2013 19:25:27 +0530
From: Chander Kashyap <chander.kashyap@...aro.org>
To: Tomasz Figa <t.figa@...sung.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
Kukjin Kim <kgene.kim@...sung.com>,
Tomasz Figa <tomasz.figa@...il.com>,
"linux-samsung-soc@...r.kernel.org"
<linux-samsung-soc@...r.kernel.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
Russell King - ARM Linux <linux@....linux.org.uk>,
Jingoo Han <jg1.han@...sung.com>,
Jonghwan Choi <jhbird.choi@...sung.com>,
Abhilash Kesavan <a.kesavan@...sung.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"stable@...r.kernel.org" <stable@...r.kernel.org>,
Kyungmin Park <kyungmin.park@...sung.com>,
Arnd Bergmann <arnd@...db.de>, Olof Johansson <olof@...om.net>,
Nicolas Pitre <nico@...aro.org>,
Will Deacon <Will.Deacon@....com>,
Stephen Boyd <sboyd@...eaurora.org>
Subject: Re: [PATCH] ARM: EXYNOS: Fix incorrect usage of S5P_ARM_CORE1_* registers
On 19 June 2013 19:19, Tomasz Figa <t.figa@...sung.com> wrote:
> On Wednesday 19 of June 2013 14:24:17 Lorenzo Pieralisi wrote:
>> On Wed, Jun 19, 2013 at 01:50:57PM +0100, Tomasz Figa wrote:
>> > On Wednesday 19 of June 2013 17:39:21 Chander Kashyap wrote:
>> > > On 18 June 2013 23:29, Kukjin Kim <kgene.kim@...sung.com> wrote:
>> > > > On 06/19/13 02:45, Tomasz Figa wrote:
>> > > >> Ccing Arnd and Olof, because I forgot to add them to git
>> > > >> send-email...
>> > > >>
>> > > >> Sorry for the noise.
>> > > >>
>> > > >> On Tuesday 18 of June 2013 17:26:31 Tomasz Figa wrote:
>> > > >>> S5P_ARM_CORE1_* registers affect only core 1. To control further
>> > > >>> cores
>> > > >>> properly another registers must be used.
>> > > >>>
>> > > >>> This patch replaces S5P_ARM_CORE1_* register definitions with
>> > > >>> S5P_ARM_CORE_*(x) macro which return addresses of registers for
>> > > >>> specified core.
>> > > >>>
>> > > >>> This fixes CPU hotplug on quad core Exynos SoCs on which
>> > > >>> currently
>> > > >>> offlining CPUs 2 or 3 caused CPU 1 to be turned off.
>> > > >>
>> > > >> Obviously this doesn't happen currently because of the if (cpu ==
>> > > >> 1),
>> > > >> but>
>> > > >
>> > > > Yes, not happened...and just note exynos5440 doesn't support
>> > > > hotplug :)
>> > > > so this is available on exynos4412 and added 5420.
>> > > >
>> > > >> if logical cpu1 turned out not to be physical cpu1, then it would
>> > > >> crash.
>> > > >>
>> > > >> Best regards,
>> > > >> Tomasz
>> > > >>
>> > > >>> In addition,
>> > > >>> bring-up of CPU 2 and 3 is fixed on boards where bootloader
>> > > >>> powers
>> > > >>> off
>> > > >>> secondary cores by default.
>> > > >
>> > > > I need to test on board about above...
>> > > >
>> > > >>> Cc: stable@...r.kernel.org
>> > > >>> Signed-off-by: Tomasz Figa<t.figa@...sung.com>
>> > > >>> Signed-off-by: Kyungmin Park<kyungmin.park@...sung.com>
>> > > >>> ---
>> > > >>>
>> > > >>> arch/arm/mach-exynos/hotplug.c | 9 +++++----
>> > > >>> arch/arm/mach-exynos/include/mach/regs-pmu.h | 10 +++++++---
>> > > >>> arch/arm/mach-exynos/platsmp.c | 9 +++++----
>> > > >>> 3 files changed, 17 insertions(+), 11 deletions(-)
>> > > >>>
>> > > >>> diff --git a/arch/arm/mach-exynos/hotplug.c
>> > > >>> b/arch/arm/mach-exynos/hotplug.c index af90cfa..c089943 100644
>> > > >>> --- a/arch/arm/mach-exynos/hotplug.c
>> > > >>> +++ b/arch/arm/mach-exynos/hotplug.c
>> > > >>> @@ -93,10 +93,11 @@ static inline void cpu_leave_lowpower(void)
>> > > >>>
>> > > >>> static inline void platform_do_lowpower(unsigned int cpu, int
>> > > >>>
>> > > >>> *spurious) {
>> > > >>>
>> > > >>> for (;;) {
>> > > >>>
>> > > >>> + void __iomem *reg_base;
>> > > >>> + unsigned int phys_cpu = cpu_logical_map(cpu);
>> > > >>>
>> > > >>> - /* make cpu1 to be turned off at next WFI command
>> > > >>> */
>> > > >>> - if (cpu == 1)
>> > > >>> - __raw_writel(0,
>> > > >>> S5P_ARM_CORE1_CONFIGURATION);
>> > > >>> + reg_base = S5P_ARM_CORE_CONFIGURATION(phys_cpu);
>> > >
>> > > Tomasz,
>> > > This will break for non-zero, MPIDR value. Say if MPIDR is 1 then
>> > > for
>> > > cpu0 phys_cpu value will be 0x100,
>> > > and address calculation will be (S5P_ARM_CORE0_CONFIGURATION +
>> > > ((0x101) * 0x80)), which is wrong.
>>
>> Honestly, I did not understand the reasoning above, please clarify.
>>
>> > Hmm, according to the code initializing __cpu_logical_map[] array this
>> > is not true.
>> >
>> > Here's the code:
>> >
>> > https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/tree/a
>> > rch/arm/kernel/setup.c?id=refs/tags/next-20130619#n468
>> >
>> > and for used macros and bitmasks:
>> >
>> > https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/tree/a
>> > rch/arm/include/asm/cputype.h?id=refs/tags/next-20130619#n45
>> >
>> > Now the structure of the MPIDR register:
>> >
>> > http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0388e/CI
>> > HEBGFG.html
>> >
>> > As you can see, the value read from the register in
>> > smp_setup_processor_id() is only the physical CPU ID, so I don't see
>> > any
>> > problem here.
>>
>> Define "physical CPU ID" :-)
>>
>> There is a problem here: the MPIDR is not an index, and the
>> cpu_logical_map is populated in arm_dt_init_cpu_maps in:
>>
>> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/arch
>> /arm/kernel/devtree.c?id=refs/tags/v3.10-rc6
>>
>> with all affinity levels.
>
> OK. This is what I was missing. Thanks.
>
>>
>> You need to perform a mapping between logical cpus and registers offset,
>> you can't use the cpu_logical_map directly for that.
>
> Hmm, can't I just extract cluster ID and CPU ID from the MPIDR value and
> use them appropriately to calculate register offsets?
That will create problem for multi-cluster systems. Say we have two
clusters then with clusterID 0 and 1. So phys-cpu will be 0x0/0x100,
0x1/0x101 ans so on.
>
> Best regards,
> Tomasz
>
>> Next accident waiting to happen is GIC code (CONFIG_GIC_NON_BANKED),
>> where cpu_logical_map is used erroneously as an index.
>>
>> Lorenzo
--
with warm regards,
Chander Kashyap
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