Documentation/IRQ.txt


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===============
What is an IRQ?
===============

An IRQ is an interrupt request from a device.
Currently they can come in over a pin, or over a packet.
Several devices may be connected to the same pin thus
sharing an IRQ.

An IRQ number is a kernel identifier used to talk about a hardware
interrupt source.  Typically this is an index into the global irq_desc
array, but except for what linux/interrupt.h implements the details
are architecture specific.

An IRQ number is an enumeration of the possible interrupt sources on a
machine.  Typically what is enumerated is the number of input pins on
all of the interrupt controller in the system.  In the case of ISA
what is enumerated are the 16 input pins on the two i8259 interrupt
controllers.

Architectures can assign additional meaning to the IRQ numbers, and
are encouraged to in the case  where there is any manual configuration
of the hardware involved.  The ISA IRQs are a classic example of
assigning this kind of additional meaning.
// SPDX-License-Identifier: GPL-2.0
/*
 * FDT related Helper functions used by the EFI stub on multiple
 * architectures. This should be #included by the EFI stub
 * implementation files.
 *
 * Copyright 2013 Linaro Limited; author Roy Franz
 */

#include <linux/efi.h>
#include <linux/libfdt.h>
#include <asm/efi.h>

#include "efistub.h"

#define EFI_DT_ADDR_CELLS_DEFAULT 2
#define EFI_DT_SIZE_CELLS_DEFAULT 2

static void fdt_update_cell_size(efi_system_table_t *sys_table, void *fdt)
{
	int offset;

	offset = fdt_path_offset(fdt, "/");
	/* Set the #address-cells and #size-cells values for an empty tree */

	fdt_setprop_u32(fdt, offset, "#address-cells", EFI_DT_ADDR_CELLS_DEFAULT);
	fdt_setprop_u32(fdt, offset, "#size-cells",    EFI_DT_SIZE_CELLS_DEFAULT);
}

static efi_status_t update_fdt(efi_system_table_t *sys_table, void *orig_fdt,
			       unsigned long orig_fdt_size,
			       void *fdt, int new_fdt_size, char *cmdline_ptr,
			       u64 initrd_addr, u64 initrd_size)
{
	int node, num_rsv;
	int status;
	u32 fdt_val32;
	u64 fdt_val64;

	/* Do some checks on provided FDT, if it exists: */
	if (orig_fdt) {
		if (fdt_check_header(orig_fdt)) {
			pr_efi_err(sys_table, "Device Tree header not valid!\n");
			return EFI_LOAD_ERROR;
		}
		/*
		 * We don't get the size of the FDT if we get if from a
		 * configuration table:
		 */
		if (orig_fdt_size && fdt_totalsize(orig_fdt) > orig_fdt_size) {
			pr_efi_err(sys_table, "Truncated device tree! foo!\n");
			return EFI_LOAD_ERROR;
		}
	}

	if (orig_fdt) {
		status = fdt_open_into(orig_fdt, fdt, new_fdt_size);
	} else {
		status = fdt_create_empty_tree(fdt, new_fdt_size);
		if (status == 0) {
			/*
			 * Any failure from the following function is
			 * non-critical:
			 */
			fdt_update_cell_size(sys_table, fdt);
		}
	}

	if (status != 0)
		goto fdt_set_fail;

	/*
	 * Delete all memory reserve map entries. When booting via UEFI,
	 * kernel will use the UEFI memory map to find reserved regions.
	 */
	num_rsv = fdt_num_mem_rsv(fdt);
	while (num_rsv-- > 0)
		fdt_del_mem_rsv(fdt, num_rsv);

	node = fdt_subnode_offset(fdt, 0, "chosen");
	if (node < 0) {
		node = fdt_add_subnode(fdt, 0, "chosen");
		if (node < 0) {
			/* 'node' is an error code when negative: */
			status = node;
			goto fdt_set_fail;
		}
	}

	if (cmdline_ptr != NULL && strlen(cmdline_ptr) > 0) {
		status = fdt_setprop(fdt, node, "bootargs", cmdline_ptr,
				     strlen(cmdline_ptr) + 1);
		if (status)
			goto fdt_set_fail;
	}

	/* Set initrd address/end in device tree, if present */
	if (initrd_size != 0) {
		u64 initrd_image_end;
		u64 initrd_image_start = cpu_to_fdt64(initrd_addr);

		status = fdt_setprop_var(fdt, node, "linux,initrd-start", initrd_image_start);
		if (status)
			goto fdt_set_fail;

		initrd_image_end = cpu_to_fdt64(initrd_addr + initrd_size);
		status = fdt_setprop_var(fdt, node, "linux,initrd-end", initrd_image_end);
		if (status)
			goto fdt_set_fail;
	}

	/* Add FDT entries for EFI runtime services in chosen node. */
	node = fdt_subnode_offset(fdt, 0, "chosen");
	fdt_val64 = cpu_to_fdt64((u64)(unsigned long)sys_table);

	status = fdt_setprop_var(fdt, node, "linux,uefi-system-table", fdt_val64);
	if (status)
		goto fdt_set_fail;

	fdt_val64 = U64_MAX; /* placeholder */

	status = fdt_setprop_var(fdt, node, "linux,uefi-mmap-start", fdt_val64);
	if (status)
		goto fdt_set_fail;

	fdt_val32 = U32_MAX; /* placeholder */

	status = fdt_setprop_var(fdt, node, "linux,uefi-mmap-size", fdt_val32);
	if (status)
		goto fdt_set_fail;

	status = fdt_setprop_var(fdt, node, "linux,uefi-mmap-desc-size", fdt_val32);
	if (status)
		goto fdt_set_fail;

	status = fdt_setprop_var(fdt, node, "linux,uefi-mmap-desc-ver", fdt_val32);
	if (status)
		goto fdt_set_fail;

	if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) {
		efi_status_t efi_status;

		efi_status = efi_get_random_bytes(sys_table, sizeof(fdt_val64),
						  (u8 *)&fdt_val64);
		if (efi_status == EFI_SUCCESS) {
			status = fdt_setprop_var(fdt, node, "kaslr-seed", fdt_val64);
			if (status)
				goto fdt_set_fail;
		} else if (efi_status != EFI_NOT_FOUND) {
			return efi_status;
		}
	}

	/* Shrink the FDT back to its minimum size: */
	fdt_pack(fdt);

	return EFI_SUCCESS;

fdt_set_fail:
	if (status == -FDT_ERR_NOSPACE)
		return EFI_BUFFER_TOO_SMALL;

	return EFI_LOAD_ERROR;
}

static efi_status_t update_fdt_memmap(void *fdt, struct efi_boot_memmap *map)
{
	int node = fdt_path_offset(fdt, "/chosen");
	u64 fdt_val64;
	u32 fdt_val32;
	int err;

	if (node < 0)
		return EFI_LOAD_ERROR;

	fdt_val64 = cpu_to_fdt64((unsigned long)*map->map);

	err = fdt_setprop_inplace_var(fdt, node, "linux,uefi-mmap-start", fdt_val64);
	if (err)
		return EFI_LOAD_ERROR;

	fdt_val32 = cpu_to_fdt32(*map->map_size);

	err = fdt_setprop_inplace_var(fdt, node, "linux,uefi-mmap-size", fdt_val32);
	if (err)
		return EFI_LOAD_ERROR;

	fdt_val32 = cpu_to_fdt32(*map->desc_size);

	err = fdt_setprop_inplace_var(fdt, node, "linux,uefi-mmap-desc-size", fdt_val32);
	if (err)
		return EFI_LOAD_ERROR;

	fdt_val32 = cpu_to_fdt32(*map->desc_ver);

	err = fdt_setprop_inplace_var(fdt, node, "linux,uefi-mmap-desc-ver", fdt_val32);
	if (err)
		return EFI_LOAD_ERROR;

	return EFI_SUCCESS;
}

#ifndef EFI_FDT_ALIGN
# define EFI_FDT_ALIGN EFI_PAGE_SIZE
#endif

struct exit_boot_struct {
	efi_memory_desc_t	*runtime_map;
	int			*runtime_entry_count;
	void			*new_fdt_addr;
};

static efi_status_t exit_boot_func(efi_system_table_t *sys_table_arg,
				   struct efi_boot_memmap *map,
				   void *priv)
{
	struct exit_boot_struct *p = priv;
	/*
	 * Update the memory map with virtual addresses. The function will also
	 * populate @runtime_map with copies of just the EFI_MEMORY_RUNTIME
	 * entries so that we can pass it straight to SetVirtualAddressMap()
	 */
	efi_get_virtmap(*map->map, *map->map_size, *map->desc_size,
			p->runtime_map, p->runtime_entry_count);

	return update_fdt_memmap(p->new_fdt_addr, map);
}

#ifndef MAX_FDT_SIZE
# define MAX_FDT_SIZE SZ_2M
#endif

/*
 * Allocate memory for a new FDT, then add EFI, commandline, and
 * initrd related fields to the FDT.  This routine increases the
 * FDT allocation size until the allocated memory is large
 * enough.  EFI allocations are in EFI_PAGE_SIZE granules,
 * which are fixed at 4K bytes, so in most cases the first
 * allocation should succeed.
 * EFI boot services are exited at the end of this function.
 * There must be no allocations between the get_memory_map()
 * call and the exit_boot_services() call, so the exiting of
 * boot services is very tightly tied to the creation of the FDT
 * with the final memory map in it.
 */

efi_status_t allocate_new_fdt_and_exit_boot(efi_system_table_t *sys_table,
					    void *handle,
					    unsigned long *new_fdt_addr,
					    unsigned long max_addr,
					    u64 initrd_addr, u64 initrd_size,
					    char *cmdline_ptr,
					    unsigned long fdt_addr,
					    unsigned long fdt_size)
{
	unsigned long map_size, desc_size, buff_size;
	u32 desc_ver;
	unsigned long mmap_key;
	efi_memory_desc_t *memory_map, *runtime_map;
	efi_status_t status;
	int runtime_entry_count;
	struct efi_boot_memmap map;
	struct exit_boot_struct priv;

	map.map		= &runtime_map;
	map.map_size	= &map_size;
	map.desc_size	= &desc_size;
	map.desc_ver	= &desc_ver;
	map.key_ptr	= &mmap_key;
	map.buff_size	= &buff_size;

	/*
	 * Get a copy of the current memory map that we will use to prepare
	 * the input for SetVirtualAddressMap(). We don't have to worry about
	 * subsequent allocations adding entries, since they could not affect
	 * the number of EFI_MEMORY_RUNTIME regions.
	 */
	status = efi_get_memory_map(sys_table, &map);
	if (status != EFI_SUCCESS) {
		pr_efi_err(sys_table, "Unable to retrieve UEFI memory map.\n");
		return status;
	}

	pr_efi(sys_table, "Exiting boot services and installing virtual address map...\n");

	m