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Message-ID: <20130619132417.GB5276@e102568-lin.cambridge.arm.com>
Date: Wed, 19 Jun 2013 14:24:17 +0100
From: Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To: Tomasz Figa <t.figa@...sung.com>
Cc: Chander Kashyap <chander.kashyap@...aro.org>,
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 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/arch/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/arch/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/CIHEBGFG.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.
You need to perform a mapping between logical cpus and registers offset,
you can't use the cpu_logical_map directly for that.
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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