From: Tomasz Figa <t.figa@samsung.com>
To: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Chander Kashyap <chander.kashyap@linaro.org>,
        Kukjin Kim <kgene.kim@samsung.com>,
        Tomasz Figa <tomasz.figa@gmail.com>,
        "linux-samsung-soc@vger.kernel.org" 
	<linux-samsung-soc@vger.kernel.org>,
        "linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
        Russell King - ARM Linux <linux@arm.linux.org.uk>,
        Jingoo Han <jg1.han@samsung.com>,
        Jonghwan Choi <jhbird.choi@samsung.com>,
        Abhilash Kesavan <a.kesavan@samsung.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "stable@vger.kernel.org" <stable@vger.kernel.org>,
        Kyungmin Park <kyungmin.park@samsung.com>,
        Arnd Bergmann <arnd@arndb.de>, Olof Johansson <olof@lixom.net>,
        Nicolas Pitre <nico@linaro.org>, Will Deacon <Will.Deacon@arm.com>,
        Stephen Boyd <sboyd@codeaurora.org>
Subject: Re: [PATCH] ARM: EXYNOS: Fix incorrect usage of S5P_ARM_CORE1_*
 registers
Date: Wed, 19 Jun 2013 15:49:43 +0200
Message-id: <2791500.rs0iL4EgjJ@amdc1227>
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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@samsung.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@vger.kernel.org
> > > >>> Signed-off-by: Tomasz Figa<t.figa@samsung.com>
> > > >>> Signed-off-by: Kyungmin Park<kyungmin.park@samsung.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?

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
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