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Commit 24fbaca0 authored by Laurent Pinchart's avatar Laurent Pinchart Committed by Tomi Valkeinen
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drm: omapdrm: Fix incorrect usage of the term 'cache coherency' 



The is_cache_coherent() function currently returns true when the mapping
is not cache-coherent. This isn't a bug as such as the callers interpret
cache-coherent as meaning that the driver has to handle the coherency
manually, but it is nonetheless very confusing. Fix it and add a bit
more documentation to explain how cached buffers are handled.

Signed-off-by: default avatarLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: default avatarTomi Valkeinen <tomi.valkeinen@ti.com>
parent d61ce7da

drivers/gpu/drm/omapdrm/omap_gem.c

+15 −7
Original line number Diff line number Diff line
@@ -719,16 +719,21 @@ int omap_gem_roll(struct drm_gem_object *obj, uint32_t roll) 
 * Memory Management & DMA Sync

 */



/**

 * shmem buffers that are mapped cached can simulate coherency via using

 * page faulting to keep track of dirty pages

/*

 * shmem buffers that are mapped cached are not coherent.

 *

 * We keep track of dirty pages using page faulting to perform cache management.

 * When a page is mapped to the CPU in read/write mode the device can't access

 * it and omap_obj->dma_addrs[i] is NULL. When a page is mapped to the device

 * the omap_obj->dma_addrs[i] is set to the DMA address, and the page is

 * unmapped from the CPU.

 */

static inline bool is_cached_coherent(struct drm_gem_object *obj)

{

	struct omap_gem_object *omap_obj = to_omap_bo(obj);



	return (omap_obj->flags & OMAP_BO_MEM_SHMEM) &&

		((omap_obj->flags & OMAP_BO_CACHE_MASK) == OMAP_BO_CACHED);

	return !((omap_obj->flags & OMAP_BO_MEM_SHMEM) &&

		((omap_obj->flags & OMAP_BO_CACHE_MASK) == OMAP_BO_CACHED));

}



/* Sync the buffer for CPU access.. note pages should already be
@@ -739,7 +744,10 @@ void omap_gem_cpu_sync_page(struct drm_gem_object *obj, int pgoff) 
	struct drm_device *dev = obj->dev;

	struct omap_gem_object *omap_obj = to_omap_bo(obj);



	if (is_cached_coherent(obj) && omap_obj->dma_addrs[pgoff]) {

	if (is_cached_coherent(obj))

		return;



	if (omap_obj->dma_addrs[pgoff]) {

		dma_unmap_page(dev->dev, omap_obj->dma_addrs[pgoff],

				PAGE_SIZE, DMA_BIDIRECTIONAL);

		omap_obj->dma_addrs[pgoff] = 0;
@@ -756,7 +764,7 @@ void omap_gem_dma_sync_buffer(struct drm_gem_object *obj, 
	struct page **pages = omap_obj->pages;

	bool dirty = false;



	if (!is_cached_coherent(obj))

	if (is_cached_coherent(obj))

		return;



	for (i = 0; i < npages; i++) {