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6c0246a458
In order to support short clock counters, provide an ABI extension.
As a whole:
u64 time, delta, cyc = read_cycle_counter();
+ if (cap_user_time_short)
+ cyc = time_cycle + ((cyc - time_cycle) & time_mask);
delta = mul_u64_u32_shr(cyc, time_mult, time_shift);
if (cap_user_time_zero)
time = time_zero + delta;
delta += time_offset;
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Leo Yan <leo.yan@linaro.org>
Link: https://lore.kernel.org/r/20200716051130.4359-6-leo.yan@linaro.org
Signed-off-by: Will Deacon <will@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.