.. SPDX-License-Identifier: GPL-2.0
=======================================
IRQ chip model (hierarchy) of LoongArch
=======================================
Currently, LoongArch based processors (e.g. Loongson-3A5000) can only work together
with LS7A chipsets. The irq chips in LoongArch computers include CPUINTC (CPU Core
Interrupt Controller), LIOINTC (Legacy I/O Interrupt Controller), EIOINTC (Extended
I/O Interrupt Controller), HTVECINTC (Hyper-Transport Vector Interrupt Controller),
PCH-PIC (Main Interrupt Controller in LS7A chipset), PCH-LPC (LPC Interrupt Controller
in LS7A chipset) and PCH-MSI (MSI Interrupt Controller).
CPUINTC is a per-core controller (in CPU), LIOINTC/EIOINTC/HTVECINTC are per-package
controllers (in CPU), while PCH-PIC/PCH-LPC/PCH-MSI are controllers out of CPU (i.e.,
in chipsets). These controllers (in other words, irqchips) are linked in a hierarchy,
and there are two models of hierarchy (legacy model and extended model).
Legacy IRQ model
================
In this model, IPI (Inter-Processor Interrupt) and CPU Local Timer interrupt go
to CPUINTC directly, CPU UARTS interrupts go to LIOINTC, while all other devices
interrupts go to PCH-PIC/PCH-LPC/PCH-MSI and gathered by HTVECINTC, and then go
to LIOINTC, and then CPUINTC::
+-----+ +---------+ +-------+
| IPI | --> | CPUINTC | <-- | Timer |
+-----+ +---------+ +-------+
^
|
+---------+ +-------+
| LIOINTC | <-- | UARTs |
+---------+ +-------+
^
|
+-----------+
| HTVECINTC |
+-----------+
^ ^
| |
+---------+ +---------+
| PCH-PIC | | PCH-MSI |
+---------+ +---------+
^ ^ ^
| | |
+---------+ +---------+ +---------+
| PCH-LPC | | Devices | | Devices |
+---------+ +---------+ +---------+
^
|
+---------+
| Devices |
+---------+
Extended IRQ model
==================
In this model, IPI (Inter-Processor Interrupt) and CPU Local Timer interrupt go
to CPUINTC directly, CPU UARTS interrupts go to LIOINTC, while all other devices
interrupts go to PCH-PIC/PCH-LPC/PCH-MSI and gathered by EIOINTC, and then go to
to CPUINTC directly::
+-----+ +---------+ +-------+
| IPI | --> | CPUINTC | <-- | Timer |
+-----+ +---------+ +-------+
^ ^
| |
+---------+ +---------+ +-------+
| EIOINTC | | LIOINTC | <-- | UARTs |
+---------+ +---------+ +-------+
^ ^
| |
+---------+ +---------+
| PCH-PIC | | PCH-MSI |
+---------+ +---------+
^ ^ ^
| | |
+---------+ +---------+ +---------+
| PCH-LPC | | Devices | | Devices |
+---------+ +---------+ +---------+
^
|
+---------+
| Devices |
+---------+
Advanced Extended IRQ model
===========================
In this model, IPI (Inter-Processor Interrupt) and CPU Local Timer interrupt go
to CPUINTC directly, CPU UARTS interrupts go to LIOINTC, PCH-MSI interrupts go
to AVECINTC, and then go to CPUINTC directly, while all other devices interrupts
go to PCH-PIC/PCH-LPC and gathered by EIOINTC, and then go to CPUINTC directly::
+-----+ +-----------------------+ +-------+
| IPI | --> | CPUINTC | <-- | Timer |
+-----+ +-----------------------+ +-------+
^ ^ ^
| | |
+---------+ +----------+ +---------+ +-------+
| EIOINTC | | AVECINTC | | LIOINTC | <-- | UARTs |
+---------+ +----------+ +---------+ +-------+
^ ^
| |
+---------+ +---------+
| PCH-PIC | | PCH-MSI |
+---------+ +---------+
^ ^ ^
| | |
+---------+ +---------+ +---------+
| Devices | | PCH-LPC | | Devices |
+---------+ +---------+ +---------+
^
|
+---------+
| Devices |
+---------+
ACPI-related definitions
========================
CPUINTC::
ACPI_MADT_TYPE_CORE_PIC;
struct acpi_madt_core_pic;
enum acpi_madt_core_pic_version;
LIOINTC::
ACPI_MADT_TYPE_LIO_PIC;
struct acpi_madt_lio_pic;
enum acpi_madt_lio_pic_version;
EIOINTC::
ACPI_MADT_TYPE_EIO_PIC;
struct acpi_madt_eio_pic;
enum acpi_madt_eio_pic_version;
HTVECINTC::
ACPI_MADT_TYPE_HT_PIC;
struct acpi_madt_ht_pic;
enum acpi_madt_ht_pic_version;
PCH-PIC::
ACPI_MADT_TYPE_BIO_PIC;
struct acpi_madt_bio_pic;
enum acpi_madt_bio_pic_version;
PCH-MSI::
ACPI_MADT_TYPE_MSI_PIC;
struct acpi_madt_msi_pic;
enum acpi_madt_msi_pic_version;
PCH-LPC::
ACPI_MADT_TYPE_LPC_PIC;
struct acpi_madt_lpc_pic;
enum acpi_madt_lpc_pic_version;
References
==========
Documentation of Loongson-3A5000:
https://github.com/loongson/LoongArch-Documentation/releases/latest/download/Loongson-3A5000-usermanual-1.02-CN.pdf (in Chinese)
https://github.com/loongson/LoongArch-Documentation/releases/latest/download/Loongson-3A5000-usermanual-1.02-EN.pdf (in English)
Documentation of Loongson's LS7A chipset:
https://github.com/loongson/LoongArch-Documentation/releases/latest/download/Loongson-7A1000-usermanual-2.00-CN.pdf (in Chinese)
https://github.com/loongson/LoongArch-Documentation/releases/latest/download/Loongson-7A1000-usermanual-2.00-EN.pdf (in English)
.. Note::
- CPUINTC is CSR.ECFG/CSR.ESTAT and its interrupt controller described
in Section 7.4 of "LoongArch Reference Manual, Vol 1";
- LIOINTC is "Legacy I/OInterrupts" described in Section 11.1 of
"Loongson 3A5000 Processor Reference Manual";
- EIOINTC is "Extended I/O Interrupts" described in Section 11.2 of
"Loongson 3A5000 Processor Reference Manual";
- HTVECINTC is "HyperTransport Interrupts" described in Section 14.3 of
"Loongson 3A5000 Processor Reference Manual";
- PCH-PIC/PCH-MSI is "Interrupt Controller" described in Section 5 of
"Loongson 7A1000 Bridge User Manual";
- PCH-LPC is "LPC Interrupts" described in Section 24.3 of
"Loongson 7A1000 Bridge User Manual".
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