1/* SPDX-License-Identifier: GPL-2.0-only */
2#ifndef _ASM_POWERPC_RTAS_WORK_AREA_H
3#define _ASM_POWERPC_RTAS_WORK_AREA_H
4
5#include <linux/build_bug.h>
6#include <linux/sizes.h>
7#include <linux/types.h>
8
9#include <asm/page.h>
10
11/**
12 * struct rtas_work_area - RTAS work area descriptor.
13 *
14 * Descriptor for a "work area" in PAPR terminology that satisfies
15 * RTAS addressing requirements.
16 */
17struct rtas_work_area {
18	/* private: Use the APIs provided below. */
19	char *buf;
20	size_t size;
21};
22
23enum {
24	/* Maximum allocation size, enforced at build time. */
25	RTAS_WORK_AREA_MAX_ALLOC_SZ = SZ_128K,
26};
27
28/**
29 * rtas_work_area_alloc() - Acquire a work area of the requested size.
30 * @size_: Allocation size. Must be compile-time constant and not more
31 *         than %RTAS_WORK_AREA_MAX_ALLOC_SZ.
32 *
33 * Allocate a buffer suitable for passing to RTAS functions that have
34 * a memory address parameter, often (but not always) referred to as a
35 * "work area" in PAPR. Although callers are allowed to block while
36 * holding a work area, the amount of memory reserved for this purpose
37 * is limited, and allocations should be short-lived. A good guideline
38 * is to release any allocated work area before returning from a
39 * system call.
40 *
41 * This function does not fail. It blocks until the allocation
42 * succeeds. To prevent deadlocks, callers are discouraged from
43 * allocating more than one work area simultaneously in a single task
44 * context.
45 *
46 * Context: This function may sleep.
47 * Return: A &struct rtas_work_area descriptor for the allocated work area.
48 */
49#define rtas_work_area_alloc(size_) ({				\
50	static_assert(__builtin_constant_p(size_));		\
51	static_assert((size_) > 0);				\
52	static_assert((size_) <= RTAS_WORK_AREA_MAX_ALLOC_SZ);	\
53	__rtas_work_area_alloc(size_);				\
54})
55
56/*
57 * Do not call __rtas_work_area_alloc() directly. Use
58 * rtas_work_area_alloc().
59 */
60struct rtas_work_area *__rtas_work_area_alloc(size_t size);
61
62/**
63 * rtas_work_area_free() - Release a work area.
64 * @area: Work area descriptor as returned from rtas_work_area_alloc().
65 *
66 * Return a work area buffer to the pool.
67 */
68void rtas_work_area_free(struct rtas_work_area *area);
69
70static inline char *rtas_work_area_raw_buf(const struct rtas_work_area *area)
71{
72	return area->buf;
73}
74
75static inline size_t rtas_work_area_size(const struct rtas_work_area *area)
76{
77	return area->size;
78}
79
80static inline phys_addr_t rtas_work_area_phys(const struct rtas_work_area *area)
81{
82	return __pa(area->buf);
83}
84
85/*
86 * Early setup for the work area allocator. Call from
87 * rtas_initialize() only.
88 */
89
90#ifdef CONFIG_PPC_PSERIES
91void rtas_work_area_reserve_arena(phys_addr_t limit);
92#else /* CONFIG_PPC_PSERIES */
93static inline void rtas_work_area_reserve_arena(phys_addr_t limit) {}
94#endif /* CONFIG_PPC_PSERIES */
95
96#endif /* _ASM_POWERPC_RTAS_WORK_AREA_H */
97