From: Serge Semin <redacted>

[ 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 <redacted>
Signed-off-by: Alexey Malahov <redacted>
Signed-off-by: Serge Semin <redacted>
Reviewed-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Paul Burton <paulburton@kernel.org>
Cc: Ralf Baechle <redacted>
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;