[PATCH V6] irqchip/sifive-plic: Fixup EOI failed when masked

[guoren@kernel.org]

From: Guo Ren <guoren@linux.alibaba.com>

When using "devm_request_threaded_irq(,,,,IRQF_ONESHOT,,)" in the driver,
only the first interrupt could be handled, and continue irq is blocked by
hw. Because the riscv plic couldn't complete masked irq source which has
been disabled in enable register. The bug was firstly reported in [1].

Here is the description of Interrupt Completion in PLIC spec [2]:

The PLIC signals it has completed executing an interrupt handler by
writing the interrupt ID it received from the claim to the claim/complete
register. The PLIC does not check whether the completion ID is the same
as the last claim ID for that target. If the completion ID does not match
an interrupt source that is currently enabled for the target, the
                         ^^ ^^^^^^^^^ ^^^^^^^
completion is silently ignored.

[1] http://lists.infradead.org/pipermail/linux-riscv/2021-July/007441.html
[2] https://github.com/riscv/riscv-plic-spec/blob/8bc15a35d07c9edf7b5d23fec9728302595ffc4d/riscv-plic.adoc

Reported-by: Vincent Pelletier <plr.vincent@gmail.com>
Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Cc: Anup Patel <anup@brainfault.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Atish Patra <atish.patra@wdc.com>
Cc: Nikita Shubin <nikita.shubin@maquefel.me>
Cc: incent Pelletier <plr.vincent@gmail.com>

---

Changes since V6:
 - Propagate to plic_irq_eoi for all riscv,plic by Nikita Shubin
 - Remove thead related codes

Changes since V5:
 - Move back to mask/unmask
 - Fixup the problem in eoi callback
 - Remove allwinner,sun20i-d1 IRQCHIP_DECLARE
 - Rewrite comment log

Changes since V4:
 - Update comment by Anup

Changes since V3:
 - Rename "c9xx" to "c900"
 - Add sifive_plic_chip and thead_plic_chip for difference

Changes since V2:
 - Add a separate compatible string "thead,c9xx-plic"
 - set irq_mask/unmask of "plic_chip" to NULL and point
   irq_enable/disable of "plic_chip" to plic_irq_mask/unmask
 - Add a detailed comment block in plic_init() about the
   differences in Claim/Completion process of RISC-V PLIC and C9xx
   PLIC.
---
 drivers/irqchip/irq-sifive-plic.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c
index cf74cfa82045..259065d271ef 100644
--- a/drivers/irqchip/irq-sifive-plic.c
+++ b/drivers/irqchip/irq-sifive-plic.c
@@ -163,7 +163,13 @@ static void plic_irq_eoi(struct irq_data *d)
 {
 	struct plic_handler *handler = this_cpu_ptr(&plic_handlers);
 
-	writel(d->hwirq, handler->hart_base + CONTEXT_CLAIM);
+	if (irqd_irq_masked(d)) {
+		plic_irq_unmask(d);
+		writel(d->hwirq, handler->hart_base + CONTEXT_CLAIM);
+		plic_irq_mask(d);
+	} else {
+		writel(d->hwirq, handler->hart_base + CONTEXT_CLAIM);
+	}
 }
 
 static struct irq_chip plic_chip = {
-- 
2.25.1