diff options
| author | Laurent Pinchart <laurent.pinchart@ideasonboard.com> | 2017-04-21 00:33:56 +0300 |
|---|---|---|
| committer | Tomi Valkeinen <tomi.valkeinen@ti.com> | 2017-06-02 10:57:07 +0300 |
| commit | 24fbaca0e20acebfcdf7468f03465d5b1966c314 (patch) | |
| tree | 3dc3b9a3a7ff8b6ca3a0b3559b15b711ceb7f811 | |
| parent | d61ce7da02a3c52317474f2a15dd610ec652d513 (diff) | |
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: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
| -rw-r--r-- | drivers/gpu/drm/omapdrm/omap_gem.c | 22 |
1 files changed, 15 insertions, 7 deletions
diff --git a/drivers/gpu/drm/omapdrm/omap_gem.c b/drivers/gpu/drm/omapdrm/omap_gem.c index 86567e591f4e..eb02a1399a10 100644 --- a/drivers/gpu/drm/omapdrm/omap_gem.c +++ b/drivers/gpu/drm/omapdrm/omap_gem.c @@ -719,16 +719,21 @@ fail: * 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++) { |