RISC-V: Resurrect the MMIO timer implementation for M-mode systems

The K210 doesn't implement rdtime in M-mode, and since that's where Linux runs
in the NOMMU systems that means we can't use rdtime. The K210 is the only
system that anyone is currently running NOMMU or M-mode on, so here we're just
inlining the timer read directly.

This also adds the CLINT driver as an !MMU dependency, as it's currently the
only timer driver availiable for these systems and without it we get a build
failure for some configurations.

Tested-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

RISC-V: Remove CLINT related code from timer and arch

Right now the RISC-V timer driver is convoluted to support:
1. Linux RISC-V S-mode (with MMU) where it will use TIME CSR for
clocksource and SBI timer calls for clockevent device.
2. Linux RISC-V M-mode (without MMU) where it will use CLINT MMIO
counter register for clocksource and CLINT MMIO compare register
for clockevent device.

We now have a separate CLINT timer driver which also provide CLINT
based IPI operations so let's remove CLINT MMIO related code from
arch/riscv directory and RISC-V timer driver.

Signed-off-by: Anup Patel <anup.patel@wdc.com>
Tested-by: Emil Renner Berhing <kernel@esmil.dk>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Reviewed-by: Atish Patra <atish.patra@wdc.com>
Reviewed-by: Palmer Dabbelt <palmerdabbelt@google.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

RISC-V: Add mechanism to provide custom IPI operations

We add mechanism to set custom IPI operations so that CLINT driver
from drivers directory can provide custom IPI operations.

Signed-off-by: Anup Patel <anup.patel@wdc.com>
Tested-by: Emil Renner Berhing <kernel@esmil.dk>
Reviewed-by: Atish Patra <atish.patra@wdc.com>
Reviewed-by: Palmer Dabbelt <palmerdabbelt@google.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

riscv: fix the IPI missing issue in nommu mode

This patch fixes the IPI(inner processor interrupt) missing issue. It
failed because it used hartid_mask to iterate for_each_cpu(), however the
cpu_mask and hartid_mask may not be always the same. It will never send the
IPI to hartid 4 because it will be skipped in for_each_cpu loop in my case.

We can reproduce this case in Qemu sifive_u machine by this command.
qemu-system-riscv64 -nographic -smp 5 -m 1G -M sifive_u -kernel \
arch/riscv/boot/loader

It will hang in csd_lock_wait(csd) because the csd_unlock(csd) is not
called. It is not called because hartid 4 doesn't receive the IPI to
release this lock. The caller hart doesn't send the IPI to hartid 4 is
because of hartid 4 is skipped in for_each_cpu(). It will be skipped is
because "(cpu) < nr_cpu_ids" is not true. The hartid is 4 and nr_cpu_ids
is 4. Therefore it should use cpumask in for_each_cpu() instead of
hartid_mask.

/* Send a message to all CPUs in the map */
arch_send_call_function_ipi_mask(cfd->cpumask_ipi);

if (wait) {
for_each_cpu(cpu, cfd->cpumask) {
call_single_data_t *csd;
csd = per_cpu_ptr(cfd->csd, cpu);
csd_lock_wait(csd);
}
}

for ((cpu) = -1; \
(cpu) = cpumask_next((cpu), (mask)), \
(cpu) < nr_cpu_ids;)

It could boot to login console after this patch applied.

Fixes: b2d36b5668f6 ("riscv: provide native clint access for M-mode")
Signed-off-by: Greentime Hu <greentime.hu@sifive.com>
Reviewed-by: Palmer Dabbelt <palmerdabbelt@google.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

riscv: provide native clint access for M-mode

RISC-V has the concept of a cpu level interrupt controller. The
interface for it is split between a standardized part that is exposed
as bits in the mstatus/sstatus register and the mie/mip/sie/sip
CRS. But the bit to actually trigger IPIs is not standardized and
just mentioned as implementable using MMIO.

Add support for IPIs using MMIO using the SiFive clint layout (which
is also shared by Ariane, Kendryte and the Qemu virt platform).
Additionally the MMIO block also supports the time value and timer
compare registers, so they are also set up using the same OF node.
Support for other layouts should also be relatively easy to add in the
future.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Anup Patel <anup@brainfault.org>
[paul.walmsley@sifive.com: update include guard format; fix checkpatch
issues; minor commit message cleanup]
Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>