drm/i915: Skip remap_io_mapping() for non-x86 platforms

Only hw that supports mappable aperture would hit this path
vm_fault_gtt/vm_fault_tmm, So we never hit this function
remap_io_mapping() in discrete, So skip this code for non-x86
architectures.

v2: use IS_ENABLED () instead of #if defined

v3: move function prototypes from i915_drv.h to i915_mm.h

v4: added kernel error message in stub function

v5: fixed compilation warnings

v6: checkpatch style

Signed-off-by: Siva Mullati <[e-mail]>
Reviewed-by: Lucas De Marchi <[e-mail]>
Signed-off-by: Lucas De Marchi <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/i915/gem/i915_gem_mman.c

···
 #include "i915_gem_ioctls.h"
 #include "i915_gem_object.h"
 #include "i915_gem_mman.h"
+#include "i915_mm.h"
 #include "i915_trace.h"
 #include "i915_user_extensions.h"
 #include "i915_gem_ttm.h"

drivers/gpu/drm/i915/i915_drv.h

···
 int i915_reg_read_ioctl(struct drm_device *dev, void *data,
 			struct drm_file *file);
 
-/* i915_mm.c */
-int remap_io_mapping(struct vm_area_struct *vma,
-		     unsigned long addr, unsigned long pfn, unsigned long size,
-		     struct io_mapping *iomap);
-int remap_io_sg(struct vm_area_struct *vma,
-		unsigned long addr, unsigned long size,
-		struct scatterlist *sgl, resource_size_t iobase);
-
 static inline int intel_hws_csb_write_index(struct drm_i915_private *i915)
 {
 	if (GRAPHICS_VER(i915) >= 11)

drivers/gpu/drm/i915/i915_mm.c

···
 
 
 #include "i915_drv.h"
+#include "i915_mm.h"
 
 struct remap_pfn {
 	struct mm_struct *mm;
···
 	struct sgt_iter sgt;
 	resource_size_t iobase;
 };
-
-static int remap_pfn(pte_t *pte, unsigned long addr, void *data)
-{
-	struct remap_pfn *r = data;
-
-	/* Special PTE are not associated with any struct page */
-	set_pte_at(r->mm, addr, pte, pte_mkspecial(pfn_pte(r->pfn, r->prot)));
-	r->pfn++;
-
-	return 0;
-}
 
 #define use_dma(io) ((io) != -1)
 
···
 	return 0;
 }
 
+#define EXPECTED_FLAGS (VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP)
+
+#if IS_ENABLED(CONFIG_X86)
+static int remap_pfn(pte_t *pte, unsigned long addr, void *data)
+{
+	struct remap_pfn *r = data;
+
+	/* Special PTE are not associated with any struct page */
+	set_pte_at(r->mm, addr, pte, pte_mkspecial(pfn_pte(r->pfn, r->prot)));
+	r->pfn++;
+
+	return 0;
+}
+
 /**
  * remap_io_mapping - remap an IO mapping to userspace
  * @vma: user vma to map to
···
 	struct remap_pfn r;
 	int err;
 
-#define EXPECTED_FLAGS (VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP)
 	GEM_BUG_ON((vma->vm_flags & EXPECTED_FLAGS) != EXPECTED_FLAGS);
 
 	/* We rely on prevalidation of the io-mapping to skip track_pfn(). */
···
 
 	return 0;
 }
+#endif
 
 /**
  * remap_io_sg - remap an IO mapping to userspace

drivers/gpu/drm/i915/i915_mm.h

···
+/* SPDX-License-Identifier: MIT */
+/*
+ * Copyright © 2021 Intel Corporation
+ */
+
+#ifndef __I915_MM_H__
+#define __I915_MM_H__
+
+#include <linux/types.h>
+
+struct vm_area_struct;
+struct io_mapping;
+struct scatterlist;
+
+#if IS_ENABLED(CONFIG_X86)
+int remap_io_mapping(struct vm_area_struct *vma,
+		     unsigned long addr, unsigned long pfn, unsigned long size,
+		     struct io_mapping *iomap);
+#else
+static inline
+int remap_io_mapping(struct vm_area_struct *vma,
+		     unsigned long addr, unsigned long pfn, unsigned long size,
+		     struct io_mapping *iomap)
+{
+	pr_err("Architecture has no %s() and shouldn't be calling this function\n", __func__);
+	WARN_ON_ONCE(1);
+	return 0;
+}
+#endif
+
+int remap_io_sg(struct vm_area_struct *vma,
+		unsigned long addr, unsigned long size,
+		struct scatterlist *sgl, resource_size_t iobase);
+
+#endif /* __I915_MM_H__ */