[PATCH 0/4] clocksource: Fix MIPS GIC and DW APB Timer for Baikal-T1 SoC support

[<Sergey.Semin@baikalelectronics.ru>]

From: Serge Semin <fancer.lancer@gmail.com>

Aside from MIPS-specific r4k timer Baikal-T1 chip also provides a functionality
of two another timers: embedded into the MIPS GIC timer and three external DW
timers available over APB bus. But we can't use them before the corresponding
drivers are properly fixed. First of all DW APB Timer shouldn't be bound to a
single CPU, since as being accessible over APB they are external with respect
to all possible CPUs. Secondly there might be more than just two DW APB Timers
in the system (Baikal-T1 has three of them), so permit the driver to use one of
them as a clocksource and the rest - for clockevents. Thirdly it's possible to
use MIPS GIC timer as a clocksource so register it in the corresponding
subsystem (the patch has been found in the Paul Burton MIPS repo so I left the
original Signed-off-by attribute). Finally in the same way as r4k timer the
MIPS GIC timer should be used with care when CPUFREQ config is enabled since in
case of CM2 the timer counting depends on the CPU reference clock frequency
while the clocksource subsystem currently doesn't support the timers with
non-stable clock.

This patchset is rebased and tested on the mainline Linux kernel 5.6-rc4:
commit 98d54f81e36b ("Linux 5.6-rc4").

Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Signed-off-by: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>
Cc: Maxim Kaurkin <Maxim.Kaurkin@baikalelectronics.ru>
Cc: Pavel Parkhomenko <Pavel.Parkhomenko@baikalelectronics.ru>
Cc: Ramil Zaripov <Ramil.Zaripov@baikalelectronics.ru>
Cc: Ekaterina Skachko <Ekaterina.Skachko@baikalelectronics.ru>
Cc: Vadim Vlasov <V.Vlasov@baikalelectronics.ru>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Paul Burton <paul.burton@imgtec.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org

Paul Burton (1):
  clocksource: mips-gic-timer: Register as sched_clock

Serge Semin (3):
  clocksource: dw_apb_timer: Set clockevent any-possible-CPU mask
  clocksource: dw_apb_timer_of: Fix missing clockevent timers
  clocksource: mips-gic-timer: Set limitations on
    clocksource/sched-clocks usage

 drivers/clocksource/dw_apb_timer.c    | 18 +++++++---------
 drivers/clocksource/dw_apb_timer_of.c |  9 +++-----
 drivers/clocksource/mips-gic-timer.c  | 30 ++++++++++++++++++++++-----
 include/linux/dw_apb_timer.h          |  2 +-
 4 files changed, 36 insertions(+), 23 deletions(-)

-- 
2.25.1