1 files changed, 96 insertions, 0 deletions
diff --git a/arch/powerpc/include/asm/rtas-work-area.h b/arch/powerpc/include/asm/rtas-work-area.h
new file mode 100644
index 000000000000..251a395dbd2e
--- /dev/null
+++ b/arch/powerpc/include/asm/rtas-work-area.h
@@ -0,0 +1,96 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef _ASM_POWERPC_RTAS_WORK_AREA_H
+#define _ASM_POWERPC_RTAS_WORK_AREA_H
+
+#include <linux/build_bug.h>
+#include <linux/sizes.h>
+#include <linux/types.h>
+
+#include <asm/page.h>
+
+/**
+ * struct rtas_work_area - RTAS work area descriptor.
+ *
+ * Descriptor for a "work area" in PAPR terminology that satisfies
+ * RTAS addressing requirements.
+ */
+struct rtas_work_area {
+	/* private: Use the APIs provided below. */
+	char *buf;
+	size_t size;
+};
+
+enum {
+	/* Maximum allocation size, enforced at build time. */
+	RTAS_WORK_AREA_MAX_ALLOC_SZ = SZ_128K,
+};
+
+/**
+ * rtas_work_area_alloc() - Acquire a work area of the requested size.
+ * @size_: Allocation size. Must be compile-time constant and not more
+ *         than %RTAS_WORK_AREA_MAX_ALLOC_SZ.
+ *
+ * Allocate a buffer suitable for passing to RTAS functions that have
+ * a memory address parameter, often (but not always) referred to as a
+ * "work area" in PAPR. Although callers are allowed to block while
+ * holding a work area, the amount of memory reserved for this purpose
+ * is limited, and allocations should be short-lived. A good guideline
+ * is to release any allocated work area before returning from a
+ * system call.
+ *
+ * This function does not fail. It blocks until the allocation
+ * succeeds. To prevent deadlocks, callers are discouraged from
+ * allocating more than one work area simultaneously in a single task
+ * context.
+ *
+ * Context: This function may sleep.
+ * Return: A &struct rtas_work_area descriptor for the allocated work area.
+ */
+#define rtas_work_area_alloc(size_) ({				\
+	static_assert(__builtin_constant_p(size_));		\
+	static_assert((size_) > 0);				\
+	static_assert((size_) <= RTAS_WORK_AREA_MAX_ALLOC_SZ);	\
+	__rtas_work_area_alloc(size_);				\
+})
+
+/*
+ * Do not call __rtas_work_area_alloc() directly. Use
+ * rtas_work_area_alloc().
+ */
+struct rtas_work_area *__rtas_work_area_alloc(size_t size);
+
+/**
+ * rtas_work_area_free() - Release a work area.
+ * @area: Work area descriptor as returned from rtas_work_area_alloc().
+ *
+ * Return a work area buffer to the pool.
+ */
+void rtas_work_area_free(struct rtas_work_area *area);
+
+static inline char *rtas_work_area_raw_buf(const struct rtas_work_area *area)
+{
+	return area->buf;
+}
+
+static inline size_t rtas_work_area_size(const struct rtas_work_area *area)
+{
+	return area->size;
+}
+
+static inline phys_addr_t rtas_work_area_phys(const struct rtas_work_area *area)
+{
+	return __pa(area->buf);
+}
+
+/*
+ * Early setup for the work area allocator. Call from
+ * rtas_initialize() only.
+ */
+
+#ifdef CONFIG_PPC_PSERIES
+void rtas_work_area_reserve_arena(phys_addr_t limit);
+#else /* CONFIG_PPC_PSERIES */
+static inline void rtas_work_area_reserve_arena(phys_addr_t limit) {}
+#endif /* CONFIG_PPC_PSERIES */
+
+#endif /* _ASM_POWERPC_RTAS_WORK_AREA_H */