At first, we prefer to use mips clockevent device, so we decrease the
rating of hpet clockevent device.
For hpet, if HPET_MIN_PROG_DELTA (minimum delta of hpet programming) is
too small and HPET_MIN_CYCLES (threshold of -ETIME checking) is too
large, then hpet_next_event() can easily return -ETIME. After commit
c6eb3f70d4 ("hrtimer: Get rid of hrtimer softirq") this will cause
a RCU stall.
So, HPET_MIN_PROG_DELTA must be sufficient that we don't re-trip the
-ETIME check -- if we do, we will return -ETIME, forward the next event
time, try to set it, return -ETIME again, and basically lock the system
up. Meanwhile, HPET_MIN_CYCLES doesn't need to be too large, 16 cycles
is enough.
This solution is similar to commit f9eccf2461 ("clocksource/drivers
/vt8500: Increase the minimum delta").
By the way, this patch ensures hpet count/compare to be 32-bit long.
Signed-off-by: Huacai Chen <chenhc@lemote.com>
Cc: John Crispin <john@phrozen.org>
Cc: Steven J . Hill <Steven.Hill@imgtec.com>
Cc: Fuxin Zhang <zhangfx@lemote.com>
Cc: Zhangjin Wu <wuzhangjin@gmail.com>
Cc: linux-mips@linux-mips.org
Cc: stable@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/13819/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This patch is borrowed from x86 hpet driver and explaind below:
Due to the overly intelligent design of HPETs, we need to workaround
the problem that the compare value which we write is already behind
the actual counter value at the point where the value hits the real
compare register. This happens for two reasons:
1) We read out the counter, add the delta and write the result to the
compare register. When a NMI hits between the read out and the write
then the counter can be ahead of the event already.
2) The write to the compare register is delayed by up to two HPET
cycles in AMD chipsets.
We can work around this by reading back the compare register to make
sure that the written value has hit the hardware. But that is bad
performance wise for the normal case where the event is far enough in
the future.
As we already know that the write can be delayed by up to two cycles
we can avoid the read back of the compare register completely if we
make the decision whether the delta has elapsed already or not based
on the following calculation:
cmp = event - actual_count;
If cmp is less than 64 HPET clock cycles, then we decide that the event
has happened already and return -ETIME. That covers the above #1 and #2
problems which would cause a wait for HPET wraparound (~306 seconds).
Signed-off-by: Huacai Chen <chenhc@lemote.com>
Cc: Aurelien Jarno <aurelien@aurel32.net>
Cc: Steven J. Hill <Steven.Hill@imgtec.com>
Cc: Fuxin Zhang <zhangfx@lemote.com>
Cc: Zhangjin Wu <wuzhangjin@gmail.com>
Cc: Huacai Chen <chenhc@lemote.com>
Cc: linux-mips@linux-mips.org
Cc: stable@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/12162/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Migrate loongson driver to the new 'set-state' interface provided by
clockevents core, the earlier 'set-mode' interface is marked obsolete
now.
This also enables us to implement callbacks for new states of clockevent
devices, for example: ONESHOT_STOPPED.
[ralf@linux-mips.org: Folded in Viresh's followon fix.]
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Huacai Chen <chenhc@lemote.com>
Cc: Michael Opdenacker <michael.opdenacker@free-electrons.com>
Cc: Hongliang Tao <taohl@lemote.com>
Cc: Valentin Rothberg <valentinrothberg@gmail.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: linux-mips@linux-mips.org
Cc: linaro-kernel@lists.linaro.org
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Patchwork: https://patchwork.linux-mips.org/patch/10608/
Patchwork: https://patchwork.linux-mips.org/patch/10883/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Currently, code of Loongson-2/3 is under loongson directory and code of
Loongson-1 is under loongson1 directory. Besides, there are Kconfig
options such as MACH_LOONGSON and MACH_LOONGSON1. This naming style is
very ugly and confusing. Since Loongson-2/3 are both 64-bit general-
purpose CPU while Loongson-1 is 32-bit SoC, we rename both file names
and Kconfig symbols from loongson/loongson1 to loongson64/loongson32.
[ralf@linux-mips.org: Resolve a number of simple conflicts.]
Signed-off-by: Huacai Chen <chenhc@lemote.com>
Cc: Steven J. Hill <Steven.Hill@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: Fuxin Zhang <zhangfx@lemote.com>
Cc: Zhangjin Wu <wuzhangjin@gmail.com>
Cc: Kelvin Cheung <keguang.zhang@gmail.com>
Patchwork: https://patchwork.linux-mips.org/patch/9790/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
