Le 16/12/2018 à 18:19, Christoph Hellwig a écrit :
The unmap methods need to transfer memory ownership back from the device to the cpu by identical means as dma_sync_*_to_cpu. I'm not sure powerpc needs to do any work in this transfer direction, but given that it does invalidate the caches in dma_sync_*_to_cpu already we should make sure we also do so on unmapping.
Why do we have to do that on unmapping ? If we are unmapping it means we are retiring the area, so why would we need to use CPU for syncing an area than won't be used anymore ?
Christophe
Signed-off-by: Christoph Hellwig <h...@lst.de> --- arch/powerpc/kernel/dma.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/kernel/dma.c b/arch/powerpc/kernel/dma.c index dbfc7056d7df..d442d23e182b 100644 --- a/arch/powerpc/kernel/dma.c +++ b/arch/powerpc/kernel/dma.c @@ -210,10 +210,15 @@ static int dma_nommu_map_sg(struct device *dev, struct scatterlist *sgl, return nents; }-static void dma_nommu_unmap_sg(struct device *dev, struct scatterlist *sg,+static void dma_nommu_unmap_sg(struct device *dev, struct scatterlist *sgl, int nents, enum dma_data_direction direction, unsigned long attrs) { + struct scatterlist *sg; + int i; + + for_each_sg(sgl, sg, nents, i) + __dma_sync_page(sg_page(sg), sg->offset, sg->length, direction); }static u64 dma_nommu_get_required_mask(struct device *dev)@@ -247,6 +252,8 @@ static inline void dma_nommu_unmap_page(struct device *dev, enum dma_data_direction direction, unsigned long attrs) { + if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC)) + __dma_sync(bus_to_virt(dma_address), size, dir); }#ifdef CONFIG_NOT_COHERENT_CACHE
