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    SubjectRe: [PATCH AUTOSEL 4.19 080/106] mips: Add udelay lpj numbers adjustment
    On 2020-06-08 19:22, Sasha Levin wrote:
    > From: Serge Semin <Sergey.Semin@baikalelectronics.ru>
    >
    > [ Upstream commit ed26aacfb5f71eecb20a51c4467da440cb719d66 ]
    >
    > Loops-per-jiffies is a special number which represents a number of
    > noop-loop cycles per CPU-scheduler quantum - jiffies. As you
    > understand aside from CPU-specific implementation it depends on
    > the CPU frequency. So when a platform has the CPU frequency fixed,
    > we have no problem and the current udelay interface will work
    > just fine. But as soon as CPU-freq driver is enabled and the cores
    > frequency changes, we'll end up with distorted udelay's. In order
    > to fix this we have to accordinly adjust the per-CPU udelay_val
    > (the same as the global loops_per_jiffy) number. This can be done
    > in the CPU-freq transition event handler. We subscribe to that event
    > in the MIPS arch time-inititalization method.
    >
    > Co-developed-by: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>
    > Signed-off-by: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>
    > Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
    > Reviewed-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
    > Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
    > Cc: Paul Burton <paulburton@kernel.org>
    > Cc: Ralf Baechle <ralf@linux-mips.org>
    > Cc: Arnd Bergmann <arnd@arndb.de>
    > Cc: Rob Herring <robh+dt@kernel.org>
    > Cc: devicetree@vger.kernel.org
    > Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
    > Signed-off-by: Sasha Levin <sashal@kernel.org>
    > ---
    > arch/mips/kernel/time.c | 70 +++++++++++++++++++++++++++++++++++++++++
    > 1 file changed, 70 insertions(+)
    >
    > diff --git a/arch/mips/kernel/time.c b/arch/mips/kernel/time.c
    > index bfe02ded25d1..1e631a484ddf 100644
    > --- a/arch/mips/kernel/time.c
    > +++ b/arch/mips/kernel/time.c
    > @@ -22,12 +22,82 @@
    > #include <linux/smp.h>
    > #include <linux/spinlock.h>
    > #include <linux/export.h>
    > +#include <linux/cpufreq.h>
    > +#include <linux/delay.h>
    >
    > #include <asm/cpu-features.h>
    > #include <asm/cpu-type.h>
    > #include <asm/div64.h>
    > #include <asm/time.h>
    >
    > +#ifdef CONFIG_CPU_FREQ
    > +
    > +static DEFINE_PER_CPU(unsigned long, pcp_lpj_ref);
    > +static DEFINE_PER_CPU(unsigned long, pcp_lpj_ref_freq);
    > +static unsigned long glb_lpj_ref;
    > +static unsigned long glb_lpj_ref_freq;
    > +
    > +static int cpufreq_callback(struct notifier_block *nb,
    > + unsigned long val, void *data)
    > +{
    > + struct cpufreq_freqs *freq = data;
    > + struct cpumask *cpus = freq->policy->cpus;
    ^^^^^^

    The policy member has been added in kernel 5.2, so kernel 4.19.129 and
    later do not build anymore when CONFIG_CPU_FREQ=y.

    --
    Aurelien Jarno GPG: 4096R/1DDD8C9B
    aurelien@aurel32.net http://www.aurel32.net

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