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[PATCH v2 2/2] hw/intc: sifive_plic: change interrupt priority register
From: |
Jim Shu |
Subject: |
[PATCH v2 2/2] hw/intc: sifive_plic: change interrupt priority register to WARL field |
Date: |
Fri, 30 Sep 2022 12:32:39 +0000 |
PLIC spec [1] requires interrupt source priority registers are WARL
field and the number of supported priority is power-of-2 to simplify SW
discovery.
Existing QEMU RISC-V machine (e.g. shakti_c) don't strictly follow PLIC
spec, whose number of supported priority is not power-of-2. Just change
each bit of interrupt priority register to WARL field when the number of
supported priority is power-of-2.
[1]
https://github.com/riscv/riscv-plic-spec/blob/master/riscv-plic.adoc#interrupt-priorities
Signed-off-by: Jim Shu <jim.shu@sifive.com>
---
hw/intc/sifive_plic.c | 21 +++++++++++++++++++--
1 file changed, 19 insertions(+), 2 deletions(-)
diff --git a/hw/intc/sifive_plic.c b/hw/intc/sifive_plic.c
index f864efa761..218ccff8bd 100644
--- a/hw/intc/sifive_plic.c
+++ b/hw/intc/sifive_plic.c
@@ -180,7 +180,15 @@ static void sifive_plic_write(void *opaque, hwaddr addr,
uint64_t value,
if (addr_between(addr, plic->priority_base, plic->num_sources << 2)) {
uint32_t irq = ((addr - plic->priority_base) >> 2) + 1;
- if (value <= plic->num_priorities) {
+ if ((plic->num_priorities + 1) & (plic->num_priorities)) {
+ /*
+ * if "num_priorities + 1" is power-of-2, make each register bit of
+ * interrupt priority WARL (Write-Any-Read-Legal). Just filter
+ * out the access to unsupported priority bits.
+ */
+ plic->source_priority[irq] = value % (plic->num_priorities + 1);
+ sifive_plic_update(plic);
+ } else if (value <= plic->num_priorities) {
plic->source_priority[irq] = value;
sifive_plic_update(plic);
}
@@ -207,7 +215,16 @@ static void sifive_plic_write(void *opaque, hwaddr addr,
uint64_t value,
uint32_t contextid = (addr & (plic->context_stride - 1));
if (contextid == 0) {
- if (value <= plic->num_priorities) {
+ if ((plic->num_priorities + 1) & (plic->num_priorities)) {
+ /*
+ * if "num_priorities + 1" is power-of-2, each register bit of
+ * interrupt priority is WARL (Write-Any-Read-Legal). Just
+ * filter out the access to unsupported priority bits.
+ */
+ plic->target_priority[addrid] = value %
+ (plic->num_priorities + 1);
+ sifive_plic_update(plic);
+ } else if (value <= plic->num_priorities) {
plic->target_priority[addrid] = value;
sifive_plic_update(plic);
}
--
2.17.1