arch/powerpc/include/asm/rtas-work-area.h

   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 */