Re: [PATCH v2 17/20] mips: Add udelay lpj numbers adjustment

[Jiaxun Yang]

On Wed, 6 May 2020 20:42:35 +0300
<Sergey.Semin@xxxxxxxxxxxxxxxxxxxx> wrote:

> From: Serge Semin <Sergey.Semin@xxxxxxxxxxxxxxxxxxxx>
> 
> 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@xxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Alexey Malahov <Alexey.Malahov@xxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Serge Semin <Sergey.Semin@xxxxxxxxxxxxxxxxxxxx>
> Cc: Thomas Bogendoerfer <tsbogend@xxxxxxxxxxxxxxxx>
> Cc: Paul Burton <paulburton@xxxxxxxxxx>
> Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
> Cc: Arnd Bergmann <arnd@xxxxxxxx>
> Cc: Rob Herring <robh+dt@xxxxxxxxxx>
> Cc: linux-pm@xxxxxxxxxxxxxxx
> Cc: devicetree@xxxxxxxxxxxxxxx

Reviewed-by: Jiaxun Yang <jiaxun.yang@xxxxxxxxxxx>

That have been absent in MIPS kernel so long!

Thanks.
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Jiaxun Yang