Currently on SMP host, all CPUs take external interrupts routed via
PLIC. All CPUs will try to claim a given external interrupt but only
one of them will succeed while other CPUs would simply resume whatever
they were doing before. This means if we have N CPUs then for every
external interrupt N-1 CPUs will always fail to claim it and waste
their CPU time.
Instead of above, external interrupts should be taken by only one CPU
and we should have provision to explicitly specify IRQ affinity from
kernel-space or user-space.
This patch provides irq_set_affinity() implementation for PLIC driver.
It also updates irq_enable() such that PLIC interrupts are only enabled
for one of CPUs specified in IRQ affinity mask.
With this patch in-place, we can change IRQ affinity at any-time from
user-space using procfs.
Example:
/ # cat /proc/interrupts
CPU0 CPU1 CPU2 CPU3
8: 44 0 0 0 SiFive PLIC 8 virtio0
10: 48 0 0 0 SiFive PLIC 10 ttyS0
IPI0: 55 663 58 363 Rescheduling interrupts
IPI1: 0 1 3 16 Function call interrupts
/ #
/ #
/ # echo 4 > /proc/irq/10/smp_affinity
/ #
/ # cat /proc/interrupts
CPU0 CPU1 CPU2 CPU3
8: 45 0 0 0 SiFive PLIC 8 virtio0
10: 160 0 17 0 SiFive PLIC 10 ttyS0
IPI0: 68 693 77 410 Rescheduling interrupts
IPI1: 0 2 3 16 Function call interrupts
Signed-off-by: Anup Patel <anup@brainfault.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
We explicitly differentiate between PLIC handler and context because
PLIC context is for given mode of HART whereas PLIC handler is per-CPU
software construct meant for handling interrupts from a particular
PLIC context.
To achieve this differentiation, we rename "nr_handlers" to "nr_contexts"
and "nr_mapped" to "nr_handlers" in plic_init().
Signed-off-by: Anup Patel <anup@brainfault.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
We have two enteries (one for M-mode and another for S-mode) in the
interrupts-extended DT property of PLIC DT node for each HART. It is
expected that firmware/bootloader will set M-mode HWIRQ line of each
HART to 0xffffffff (i.e. -1) in interrupts-extended DT property
because Linux runs in S-mode only.
If firmware/bootloader is buggy then it will not correctly update
interrupts-extended DT property which might result in a plic_handler
configured twice. This patch adds a warning in plic_init() if a
plic_handler is already marked present. This warning provides us
a hint about incorrectly updated interrupts-extended DT property.
Signed-off-by: Anup Patel <anup@brainfault.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
This patch does following optimizations:
1. Pre-compute hart base for each context handler
2. Pre-compute enable base for each context handler
3. Have enable lock for each context handler instead
of global plic_toggle_lock
Signed-off-by: Anup Patel <anup@brainfault.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
riscv_hartid_to_cpuid can return invalid cpuid for a hart that is
present in DT but was never brought up.
Print the appropriate warning message and continue.
Signed-off-by: Atish Patra <atish.patra@wdc.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Setup the cpu_logical_map during boot. Moreover, every SBI call
and PLIC context are based on the physical hartid. Use the logical
CPU to hartid mapping to pass correct hartid to respective functions.
Signed-off-by: Atish Patra <atish.patra@wdc.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>
It's a bit confusing exactly what this function does: it actually
returns the hartid of an OF processor node, failing with -1 on invalid
nodes. I've changed the name to _hartid() in order to make that a bit
more clear, as well as adding a comment.
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>
[Atish: code comment formatting update]
Signed-off-by: Atish Patra <atish.patra@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>
Add a driver for the SiFive implementation of the RISC-V Platform Level
Interrupt Controller (PLIC). The PLIC connects global interrupt sources
to the local interrupt controller on each hart.
This driver is based on the driver in the RISC-V tree from Palmer Dabbelt,
but has been almost entirely rewritten since, and includes many fixes
from Atish Patra.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Atish Patra <atish.patra@wdc.com>
[Binding update by Palmer]
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>
