Messages in this thread | | | Date | Tue, 8 Mar 2016 09:59:07 +0000 | From | Russell King - ARM Linux <> | Subject | Re: [PATCH] tty: amba-pl011: use sg_table instead of scatterlist |
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On Tue, Mar 08, 2016 at 11:43:36AM +0900, Chanho Min wrote: > The use of phys_to_page is wrong in commit cb06ff102e2d ("ARM: PL011: > Add support for Rx DMA buffer polling."), beacase DMA address is not > physical address. Also, phys_to_page is not declared in some architecture. > The use of virt_to_page is wrong as well because dma_alloc_coherent > implementaion are allowed to returned remapped memory. So I use sg_table > instead of scatterlist and change to dma_get_sgtable() implementaion.
dma_get_sgtable() is also broken.
> @@ -344,17 +344,23 @@ static int pl011_sgbuf_init(struct dma_chan *chan, struct pl011_sgbuf *sg, > enum dma_data_direction dir) > { > dma_addr_t dma_addr; > + int ret; > > sg->buf = dma_alloc_coherent(chan->device->dev, > PL011_DMA_BUFFER_SIZE, &dma_addr, GFP_KERNEL); > if (!sg->buf) > return -ENOMEM;
sg->buf can be a mapped address, which virt_to_page() will return invalid results:
int dma_common_get_sgtable(struct device *dev, struct sg_table *sgt, void *cpu_addr, dma_addr_t handle, size_t size) { struct page *page = virt_to_page(cpu_addr); int ret;
ret = sg_alloc_table(sgt, 1, GFP_KERNEL); if (unlikely(ret)) return ret;
sg_set_page(sgt->sgl, page, PAGE_ALIGN(size), 0); return 0; } EXPORT_SYMBOL(dma_common_get_sgtable);
I've no idea who is shoveling crap like this into the kernel, but it's _really_ far from good that such broken abstractions are being merged as generic code.
-- RMK's Patch system: http://www.arm.linux.org.uk/developer/patches/ FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net.
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