sb,soc/intel: Set IOAPIC redirection entry count
The number of redirection table entries (aka interrupt vectors) inside
an I/O APIC may depend of the SKU, with the related register being of
type read/write-once. Provide support utilities to either lock or set
this registers value.
Change-Id: I8da869ba390dd821b43032e4ccbc9291c39e6bab
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/55289
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
diff --git a/src/arch/x86/ioapic.c b/src/arch/x86/ioapic.c
index 1d30baa..22d979d 100644
--- a/src/arch/x86/ioapic.c
+++ b/src/arch/x86/ioapic.c
@@ -27,18 +27,44 @@
vector, high, low);
}
-static int ioapic_interrupt_count(void *ioapic_base)
+/* Bits 23-16 of register 0x01 specify the maximum redirection entry, which
+ * is the number of interrupts minus 1. */
+unsigned int ioapic_get_max_vectors(void *ioapic_base)
{
- /* Read the available number of interrupts. */
- int ioapic_interrupts = (io_apic_read(ioapic_base, 0x01) >> 16) & 0xff;
- if (!ioapic_interrupts || ioapic_interrupts == 0xff)
- ioapic_interrupts = 23;
- ioapic_interrupts += 1; /* Bits 23-16 specify the maximum redirection
- entry, which is the number of interrupts
- minus 1. */
- printk(BIOS_DEBUG, "IOAPIC: %d interrupts\n", ioapic_interrupts);
+ u32 reg;
+ u8 count;
- return ioapic_interrupts;
+ reg = io_apic_read(ioapic_base, 0x01);
+ count = reg >> 16;
+
+ if (!count || count == 0xff)
+ count = 23;
+ count++;
+
+ printk(BIOS_DEBUG, "IOAPIC: %d interrupts\n", count);
+ return count;
+}
+
+/* Set maximum number of redirection entries (MRE). It is write-once register
+ * for some chipsets, and a negative mre_count will lock it to the number
+ * of vectors read from the register. */
+void ioapic_set_max_vectors(void *ioapic_base, int mre_count)
+{
+ u32 reg;
+ u8 count;
+
+ reg = io_apic_read(ioapic_base, 0x01);
+ count = reg >> 16;
+ if (mre_count > 0)
+ count = mre_count - 1;
+ reg &= ~(0xff << 16);
+ reg |= count << 16;
+ io_apic_write(ioapic_base, 0x01, count);
+}
+
+void ioapic_lock_max_vectors(void *ioapic_base)
+{
+ ioapic_set_max_vectors(ioapic_base, -1);
}
static void clear_vectors(void *ioapic_base, u8 first, u8 last)
@@ -134,6 +160,6 @@
void setup_ioapic(void *ioapic_base, u8 ioapic_id)
{
set_ioapic_id(ioapic_base, ioapic_id);
- clear_vectors(ioapic_base, 0, ioapic_interrupt_count(ioapic_base) - 1);
+ clear_vectors(ioapic_base, 0, ioapic_get_max_vectors(ioapic_base) - 1);
route_i8259_irq0(ioapic_base);
}