[PATCH v3 14/16] hw/intc: sifive_plic: Change "priority-base" to start from interrupt source 0

[Bin Meng]

At present the SiFive PLIC model "priority-base" expects interrupt
priority register base starting from source 1 instead source 0,
that's why on most platforms "priority-base" is set to 0x04 except
'opentitan' machine. 'opentitan' should have set "priority-base"
to 0x04 too.

Note the irq number calculation in sifive_plic_{read,write} is
correct as the codes make up for the irq number by adding 1.

Let's simply update "priority-base" to start from interrupt source
0 and add a comment to make it crystal clear.

Signed-off-by: Bin Meng <bmeng@tinylab.org>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Wilfred Mallawa <wilfred.mallawa@wdc.com>
---

(no changes since v1)

 include/hw/riscv/microchip_pfsoc.h | 2 +-
 include/hw/riscv/shakti_c.h        | 2 +-
 include/hw/riscv/sifive_e.h        | 2 +-
 include/hw/riscv/sifive_u.h        | 2 +-
 include/hw/riscv/virt.h            | 2 +-
 hw/intc/sifive_plic.c              | 5 +++--
 6 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/include/hw/riscv/microchip_pfsoc.h 
b/include/hw/riscv/microchip_pfsoc.h
index 577efad0c4..e65ffeb02d 100644
--- a/include/hw/riscv/microchip_pfsoc.h
+++ b/include/hw/riscv/microchip_pfsoc.h
@@ -155,7 +155,7 @@ enum {
 
 #define MICROCHIP_PFSOC_PLIC_NUM_SOURCES        187
 #define MICROCHIP_PFSOC_PLIC_NUM_PRIORITIES     7
-#define MICROCHIP_PFSOC_PLIC_PRIORITY_BASE      0x04
+#define MICROCHIP_PFSOC_PLIC_PRIORITY_BASE      0x00
 #define MICROCHIP_PFSOC_PLIC_PENDING_BASE       0x1000
 #define MICROCHIP_PFSOC_PLIC_ENABLE_BASE        0x2000
 #define MICROCHIP_PFSOC_PLIC_ENABLE_STRIDE      0x80
diff --git a/include/hw/riscv/shakti_c.h b/include/hw/riscv/shakti_c.h
index daf0aae13f..539fe1156d 100644
--- a/include/hw/riscv/shakti_c.h
+++ b/include/hw/riscv/shakti_c.h
@@ -65,7 +65,7 @@ enum {
 #define SHAKTI_C_PLIC_NUM_SOURCES 28
 /* Excluding Priority 0 */
 #define SHAKTI_C_PLIC_NUM_PRIORITIES 2
-#define SHAKTI_C_PLIC_PRIORITY_BASE 0x04
+#define SHAKTI_C_PLIC_PRIORITY_BASE 0x00
 #define SHAKTI_C_PLIC_PENDING_BASE 0x1000
 #define SHAKTI_C_PLIC_ENABLE_BASE 0x2000
 #define SHAKTI_C_PLIC_ENABLE_STRIDE 0x80
diff --git a/include/hw/riscv/sifive_e.h b/include/hw/riscv/sifive_e.h
index 9e58247fd8..b824a79e2d 100644
--- a/include/hw/riscv/sifive_e.h
+++ b/include/hw/riscv/sifive_e.h
@@ -89,7 +89,7 @@ enum {
  */
 #define SIFIVE_E_PLIC_NUM_SOURCES 53
 #define SIFIVE_E_PLIC_NUM_PRIORITIES 7
-#define SIFIVE_E_PLIC_PRIORITY_BASE 0x04
+#define SIFIVE_E_PLIC_PRIORITY_BASE 0x00
 #define SIFIVE_E_PLIC_PENDING_BASE 0x1000
 #define SIFIVE_E_PLIC_ENABLE_BASE 0x2000
 #define SIFIVE_E_PLIC_ENABLE_STRIDE 0x80
diff --git a/include/hw/riscv/sifive_u.h b/include/hw/riscv/sifive_u.h
index 8f63a183c4..e680d61ece 100644
--- a/include/hw/riscv/sifive_u.h
+++ b/include/hw/riscv/sifive_u.h
@@ -158,7 +158,7 @@ enum {
 
 #define SIFIVE_U_PLIC_NUM_SOURCES 54
 #define SIFIVE_U_PLIC_NUM_PRIORITIES 7
-#define SIFIVE_U_PLIC_PRIORITY_BASE 0x04
+#define SIFIVE_U_PLIC_PRIORITY_BASE 0x00
 #define SIFIVE_U_PLIC_PENDING_BASE 0x1000
 #define SIFIVE_U_PLIC_ENABLE_BASE 0x2000
 #define SIFIVE_U_PLIC_ENABLE_STRIDE 0x80
diff --git a/include/hw/riscv/virt.h b/include/hw/riscv/virt.h
index e1ce0048af..3407c9e8dd 100644
--- a/include/hw/riscv/virt.h
+++ b/include/hw/riscv/virt.h
@@ -98,7 +98,7 @@ enum {
 #define VIRT_IRQCHIP_MAX_GUESTS_BITS 3
 #define VIRT_IRQCHIP_MAX_GUESTS ((1U << VIRT_IRQCHIP_MAX_GUESTS_BITS) - 1U)
 
-#define VIRT_PLIC_PRIORITY_BASE 0x04
+#define VIRT_PLIC_PRIORITY_BASE 0x00
 #define VIRT_PLIC_PENDING_BASE 0x1000
 #define VIRT_PLIC_ENABLE_BASE 0x2000
 #define VIRT_PLIC_ENABLE_STRIDE 0x80
diff --git a/hw/intc/sifive_plic.c b/hw/intc/sifive_plic.c
index 1edeb1e1ed..1a792cc3f5 100644
--- a/hw/intc/sifive_plic.c
+++ b/hw/intc/sifive_plic.c
@@ -140,7 +140,7 @@ static uint64_t sifive_plic_read(void *opaque, hwaddr addr, 
unsigned size)
     SiFivePLICState *plic = opaque;
 
     if (addr_between(addr, plic->priority_base, plic->num_sources << 2)) {
-        uint32_t irq = ((addr - plic->priority_base) >> 2) + 1;
+        uint32_t irq = (addr - plic->priority_base) >> 2;
 
         return plic->source_priority[irq];
     } else if (addr_between(addr, plic->pending_base, plic->num_sources >> 3)) 
{
@@ -187,7 +187,7 @@ static void sifive_plic_write(void *opaque, hwaddr addr, 
uint64_t value,
     SiFivePLICState *plic = opaque;
 
     if (addr_between(addr, plic->priority_base, plic->num_sources << 2)) {
-        uint32_t irq = ((addr - plic->priority_base) >> 2) + 1;
+        uint32_t irq = (addr - plic->priority_base) >> 2;
 
         if (((plic->num_priorities + 1) & plic->num_priorities) == 0) {
             /*
@@ -428,6 +428,7 @@ static Property sifive_plic_properties[] = {
     /* number of interrupt sources including interrupt source 0 */
     DEFINE_PROP_UINT32("num-sources", SiFivePLICState, num_sources, 1),
     DEFINE_PROP_UINT32("num-priorities", SiFivePLICState, num_priorities, 0),
+    /* interrupt priority register base starting from source 0 */
     DEFINE_PROP_UINT32("priority-base", SiFivePLICState, priority_base, 0),
     DEFINE_PROP_UINT32("pending-base", SiFivePLICState, pending_base, 0),
     DEFINE_PROP_UINT32("enable-base", SiFivePLICState, enable_base, 0),
-- 
2.34.1