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.