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  */
17 struct rtas_work_area {
18 	/* private: Use the APIs provided below. */
19 	char *buf;
20 	size_t size;
21 };
22 
23 enum {
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  */
60 struct 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  */
68 void rtas_work_area_free(struct rtas_work_area *area);
69 
70 static inline char *rtas_work_area_raw_buf(const struct rtas_work_area *area)
71 {
72 	return area->buf;
73 }
74 
75 static inline size_t rtas_work_area_size(const struct rtas_work_area *area)
76 {
77 	return area->size;
78 }
79 
80 static 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
91 void rtas_work_area_reserve_arena(phys_addr_t limit);
92 #else /* CONFIG_PPC_PSERIES */
93 static 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