From 5fbc2c2bfa5c9daf885e51038e66645916e83966 Mon Sep 17 00:00:00 2001 From: Imre Deak Date: Wed, 20 Jan 2021 23:38:34 +0200 Subject: [PATCH] drm/i915/gem: Add a helper to read data from a GEM object page Add a simple helper to read data with the CPU from the page of a GEM object. Do the read either via a kmap if the object has struct pages or an iomap otherwise. This is needed by the next patch, reading a u64 value from the object (w/o requiring the obj to be mapped to the GPU). Suggested by Chris. v2 (Chris): - Sanitize the type and order of func params. - Avoid consts requiring too many casts. - Use BUG_ON instead of WARN_ON, simplify the conditions. - Fix __iomem sparse errors. - Leave locking/syncing/pinning up to the caller, require only that the caller has pinned the object pages. - Check for iomem backing store before reading via an iomap. v3: - Fix offset passed to io_mapping_map_wc() missing a mem.region.start delta. (Chris, Matthew) Cc: Chris Wilson Cc: Matthew Auld Signed-off-by: Imre Deak Reviewed-by: Chris Wilson Link: https://patchwork.freedesktop.org/patch/msgid/20210120213834.1435710-1-imre.deak@intel.com --- drivers/gpu/drm/i915/gem/i915_gem_object.c | 65 ++++++++++++++++++++++++++++++ drivers/gpu/drm/i915/gem/i915_gem_object.h | 8 ++++ 2 files changed, 73 insertions(+) diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.c b/drivers/gpu/drm/i915/gem/i915_gem_object.c index 00d24000b5e8..acae93199957 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_object.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_object.c @@ -32,6 +32,7 @@ #include "i915_gem_mman.h" #include "i915_gem_object.h" #include "i915_globals.h" +#include "i915_memcpy.h" #include "i915_trace.h" static struct i915_global_object { @@ -383,6 +384,70 @@ void __i915_gem_object_invalidate_frontbuffer(struct drm_i915_gem_object *obj, } } +static void +i915_gem_object_read_from_page_kmap(struct drm_i915_gem_object *obj, u64 offset, void *dst, int size) +{ + void *src_map; + void *src_ptr; + + src_map = kmap_atomic(i915_gem_object_get_page(obj, offset >> PAGE_SHIFT)); + + src_ptr = src_map + offset_in_page(offset); + if (!(obj->cache_coherent & I915_BO_CACHE_COHERENT_FOR_READ)) + drm_clflush_virt_range(src_ptr, size); + memcpy(dst, src_ptr, size); + + kunmap_atomic(src_map); +} + +static void +i915_gem_object_read_from_page_iomap(struct drm_i915_gem_object *obj, u64 offset, void *dst, int size) +{ + void __iomem *src_map; + void __iomem *src_ptr; + dma_addr_t dma = i915_gem_object_get_dma_address(obj, offset >> PAGE_SHIFT); + + src_map = io_mapping_map_wc(&obj->mm.region->iomap, + dma - obj->mm.region->region.start, + PAGE_SIZE); + + src_ptr = src_map + offset_in_page(offset); + if (!i915_memcpy_from_wc(dst, (void __force *)src_ptr, size)) + memcpy_fromio(dst, src_ptr, size); + + io_mapping_unmap(src_map); +} + +/** + * i915_gem_object_read_from_page - read data from the page of a GEM object + * @obj: GEM object to read from + * @offset: offset within the object + * @dst: buffer to store the read data + * @size: size to read + * + * Reads data from @obj at the specified offset. The requested region to read + * from can't cross a page boundary. The caller must ensure that @obj pages + * are pinned and that @obj is synced wrt. any related writes. + * + * Returns 0 on success or -ENODEV if the type of @obj's backing store is + * unsupported. + */ +int i915_gem_object_read_from_page(struct drm_i915_gem_object *obj, u64 offset, void *dst, int size) +{ + GEM_BUG_ON(offset >= obj->base.size); + GEM_BUG_ON(offset_in_page(offset) > PAGE_SIZE - size); + GEM_BUG_ON(!i915_gem_object_has_pinned_pages(obj)); + + if (i915_gem_object_has_struct_page(obj)) + i915_gem_object_read_from_page_kmap(obj, offset, dst, size); + else if (i915_gem_object_has_iomem(obj)) + i915_gem_object_read_from_page_iomap(obj, offset, dst, size); + else + return -ENODEV; + + return 0; +} + void i915_gem_init__objects(struct drm_i915_private *i915) { INIT_WORK(&i915->mm.free_work, __i915_gem_free_work); diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.h b/drivers/gpu/drm/i915/gem/i915_gem_object.h index be14486f63a7..ae83737f1d48 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_object.h +++ b/drivers/gpu/drm/i915/gem/i915_gem_object.h @@ -201,6 +201,12 @@ i915_gem_object_has_struct_page(const struct drm_i915_gem_object *obj) } static inline bool +i915_gem_object_has_iomem(const struct drm_i915_gem_object *obj) +{ + return i915_gem_object_type_has(obj, I915_GEM_OBJECT_HAS_IOMEM); +} + +static inline bool i915_gem_object_is_shrinkable(const struct drm_i915_gem_object *obj) { return i915_gem_object_type_has(obj, I915_GEM_OBJECT_IS_SHRINKABLE); @@ -540,4 +546,6 @@ i915_gem_object_invalidate_frontbuffer(struct drm_i915_gem_object *obj, __i915_gem_object_invalidate_frontbuffer(obj, origin); } +int i915_gem_object_read_from_page(struct drm_i915_gem_object *obj, u64 offset, void *dst, int size); + #endif -- 2.11.0