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Subject[PATCH v4 5/6] drm/nouveau: implement explicitly coherent BOs
Date
Allow nouveau_bo_new() to recognize the TTM_PL_FLAG_UNCACHED flag, which
means that we want the allocated BO to be perfectly coherent between the
CPU and GPU. This is useful on non-coherent architectures for which we
do not want to manually sync some rarely-accessed buffers: typically,
fences and pushbuffers.

A TTM BO allocated with the TTM_PL_FLAG_UNCACHED on a non-coherent
architecture will be populated using the DMA API, and accesses to it
performed using the coherent mapping performed by dma_alloc_coherent().

Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
---
drivers/gpu/drm/nouveau/nouveau_bo.c | 76 ++++++++++++++++++++++++++++++++----
drivers/gpu/drm/nouveau/nouveau_bo.h | 1 +
2 files changed, 69 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nouveau_bo.c b/drivers/gpu/drm/nouveau/nouveau_bo.c
index 47e4e8886769..23a29adfabf0 100644
--- a/drivers/gpu/drm/nouveau/nouveau_bo.c
+++ b/drivers/gpu/drm/nouveau/nouveau_bo.c
@@ -219,6 +219,9 @@ nouveau_bo_new(struct drm_device *dev, int size, int align,
nvbo->tile_flags = tile_flags;
nvbo->bo.bdev = &drm->ttm.bdev;

+ if (!nv_device_is_cpu_coherent(nouveau_dev(dev)))
+ nvbo->force_coherent = flags & TTM_PL_FLAG_UNCACHED;
+
nvbo->page_shift = 12;
if (drm->client.base.vm) {
if (!(flags & TTM_PL_FLAG_TT) && size > 256 * 1024)
@@ -289,8 +292,9 @@ void
nouveau_bo_placement_set(struct nouveau_bo *nvbo, uint32_t type, uint32_t busy)
{
struct ttm_placement *pl = &nvbo->placement;
- uint32_t flags = TTM_PL_MASK_CACHING |
- (nvbo->pin_refcnt ? TTM_PL_FLAG_NO_EVICT : 0);
+ uint32_t flags = (nvbo->force_coherent ? TTM_PL_FLAG_UNCACHED :
+ TTM_PL_MASK_CACHING) |
+ (nvbo->pin_refcnt ? TTM_PL_FLAG_NO_EVICT : 0);

pl->placement = nvbo->placements;
set_placement_list(nvbo->placements, &pl->num_placement,
@@ -390,7 +394,14 @@ nouveau_bo_map(struct nouveau_bo *nvbo)
if (ret)
return ret;

- ret = ttm_bo_kmap(&nvbo->bo, 0, nvbo->bo.mem.num_pages, &nvbo->kmap);
+ /*
+ * TTM buffers allocated using the DMA API already have a mapping, let's
+ * use it instead.
+ */
+ if (!nvbo->force_coherent)
+ ret = ttm_bo_kmap(&nvbo->bo, 0, nvbo->bo.mem.num_pages,
+ &nvbo->kmap);
+
ttm_bo_unreserve(&nvbo->bo);
return ret;
}
@@ -398,7 +409,14 @@ nouveau_bo_map(struct nouveau_bo *nvbo)
void
nouveau_bo_unmap(struct nouveau_bo *nvbo)
{
- if (nvbo)
+ if (!nvbo)
+ return;
+
+ /*
+ * TTM buffers allocated using the DMA API already had a coherent
+ * mapping which we used, no need to unmap.
+ */
+ if (!nvbo->force_coherent)
ttm_bo_kunmap(&nvbo->kmap);
}

@@ -482,12 +500,36 @@ nouveau_bo_validate(struct nouveau_bo *nvbo, bool interruptible,
return 0;
}

+static inline void *
+_nouveau_bo_mem_index(struct nouveau_bo *nvbo, unsigned index, void *mem, u8 sz)
+{
+ struct ttm_dma_tt *dma_tt;
+ u8 *m = mem;
+
+ index *= sz;
+
+ if (m) {
+ /* kmap'd address, return the corresponding offset */
+ m += index;
+ } else {
+ /* DMA-API mapping, lookup the right address */
+ dma_tt = (struct ttm_dma_tt *)nvbo->bo.ttm;
+ m = dma_tt->cpu_address[index / PAGE_SIZE];
+ m += index % PAGE_SIZE;
+ }
+
+ return m;
+}
+#define nouveau_bo_mem_index(o, i, m) _nouveau_bo_mem_index(o, i, m, sizeof(*m))
+
u16
nouveau_bo_rd16(struct nouveau_bo *nvbo, unsigned index)
{
bool is_iomem;
u16 *mem = ttm_kmap_obj_virtual(&nvbo->kmap, &is_iomem);
- mem = &mem[index];
+
+ mem = nouveau_bo_mem_index(nvbo, index, mem);
+
if (is_iomem)
return ioread16_native((void __force __iomem *)mem);
else
@@ -499,7 +541,9 @@ nouveau_bo_wr16(struct nouveau_bo *nvbo, unsigned index, u16 val)
{
bool is_iomem;
u16 *mem = ttm_kmap_obj_virtual(&nvbo->kmap, &is_iomem);
- mem = &mem[index];
+
+ mem = nouveau_bo_mem_index(nvbo, index, mem);
+
if (is_iomem)
iowrite16_native(val, (void __force __iomem *)mem);
else
@@ -511,7 +555,9 @@ nouveau_bo_rd32(struct nouveau_bo *nvbo, unsigned index)
{
bool is_iomem;
u32 *mem = ttm_kmap_obj_virtual(&nvbo->kmap, &is_iomem);
- mem = &mem[index];
+
+ mem = nouveau_bo_mem_index(nvbo, index, mem);
+
if (is_iomem)
return ioread32_native((void __force __iomem *)mem);
else
@@ -523,7 +569,9 @@ nouveau_bo_wr32(struct nouveau_bo *nvbo, unsigned index, u32 val)
{
bool is_iomem;
u32 *mem = ttm_kmap_obj_virtual(&nvbo->kmap, &is_iomem);
- mem = &mem[index];
+
+ mem = nouveau_bo_mem_index(nvbo, index, mem);
+
if (is_iomem)
iowrite32_native(val, (void __force __iomem *)mem);
else
@@ -1426,6 +1474,14 @@ nouveau_ttm_tt_populate(struct ttm_tt *ttm)
device = nv_device(drm->device);
dev = drm->dev;

+ /*
+ * Objects matching this condition have been marked as force_coherent,
+ * so use the DMA API for them.
+ */
+ if (!nv_device_is_cpu_coherent(device) &&
+ ttm->caching_state == tt_uncached)
+ return ttm_dma_populate(ttm_dma, dev->dev);
+
#if __OS_HAS_AGP
if (drm->agp.stat == ENABLED) {
return ttm_agp_tt_populate(ttm);
@@ -1476,6 +1532,10 @@ nouveau_ttm_tt_unpopulate(struct ttm_tt *ttm)
device = nv_device(drm->device);
dev = drm->dev;

+ if (!nv_device_is_cpu_coherent(device) &&
+ ttm->caching_state == tt_uncached)
+ ttm_dma_unpopulate(ttm_dma, dev->dev);
+
#if __OS_HAS_AGP
if (drm->agp.stat == ENABLED) {
ttm_agp_tt_unpopulate(ttm);
diff --git a/drivers/gpu/drm/nouveau/nouveau_bo.h b/drivers/gpu/drm/nouveau/nouveau_bo.h
index fa42298d2dca..9a111b92fb34 100644
--- a/drivers/gpu/drm/nouveau/nouveau_bo.h
+++ b/drivers/gpu/drm/nouveau/nouveau_bo.h
@@ -11,6 +11,7 @@ struct nouveau_bo {
u32 valid_domains;
u32 placements[3];
u32 busy_placements[3];
+ bool force_coherent;
struct ttm_bo_kmap_obj kmap;
struct list_head head;

--
2.0.0


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