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diff --git a/Documentation/arch/loongarch/irq-chip-model.rst b/Documentation/arch/loongarch/irq-chip-model.rst new file mode 100644 index 000000000000..8f5c3345109e --- /dev/null +++ b/Documentation/arch/loongarch/irq-chip-model.rst @@ -0,0 +1,256 @@ +.. 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 | + +---------+ + +Virtual Extended IRQ model +========================== + +In this model, IPI (Inter-Processor Interrupt) and CPU Local Timer interrupt +go to CPUINTC directly, CPU UARTS interrupts go to PCH-PIC, while all other +devices interrupts go to PCH-PIC/PCH-MSI and gathered by V-EIOINTC (Virtual +Extended I/O Interrupt Controller), and then go to CPUINTC directly:: + + +-----+ +-------------------+ +-------+ + | IPI |--> | CPUINTC(0-255vcpu)| <-- | Timer | + +-----+ +-------------------+ +-------+ + ^ + | + +-----------+ + | V-EIOINTC | + +-----------+ + ^ ^ + | | + +---------+ +---------+ + | PCH-PIC | | PCH-MSI | + +---------+ +---------+ + ^ ^ ^ + | | | + +--------+ +---------+ +---------+ + | UARTs | | Devices | | Devices | + +--------+ +---------+ +---------+ + + +Description +----------- +V-EIOINTC (Virtual Extended I/O Interrupt Controller) is an extension of +EIOINTC, it only works in VM mode which runs in KVM hypervisor. Interrupts can +be routed to up to four vCPUs via standard EIOINTC, however with V-EIOINTC +interrupts can be routed to up to 256 virtual cpus. + +With standard EIOINTC, interrupt routing setting includes two parts: eight +bits for CPU selection and four bits for CPU IP (Interrupt Pin) selection. +For CPU selection there is four bits for EIOINTC node selection, four bits +for EIOINTC CPU selection. Bitmap method is used for CPU selection and +CPU IP selection, so interrupt can only route to CPU0 - CPU3 and IP0-IP3 in +one EIOINTC node. + +With V-EIOINTC it supports to route more CPUs and CPU IP (Interrupt Pin), +there are two newly added registers with V-EIOINTC. + +EXTIOI_VIRT_FEATURES +-------------------- +This register is read-only register, which indicates supported features with +V-EIOINTC. Feature EXTIOI_HAS_INT_ENCODE and EXTIOI_HAS_CPU_ENCODE is added. + +Feature EXTIOI_HAS_INT_ENCODE is part of standard EIOINTC. If it is 1, it +indicates that CPU Interrupt Pin selection can be normal method rather than +bitmap method, so interrupt can be routed to IP0 - IP15. + +Feature EXTIOI_HAS_CPU_ENCODE is extension of V-EIOINTC. If it is 1, it +indicates that CPU selection can be normal method rather than bitmap method, +so interrupt can be routed to CPU0 - CPU255. + +EXTIOI_VIRT_CONFIG +------------------ +This register is read-write register, for compatibility interrupt routed uses +the default method which is the same with standard EIOINTC. If the bit is set +with 1, it indicated HW to use normal method rather than bitmap method. + +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". |