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SubjectRE: [PATCH] tty: amba-pl011: use sg_table instead of scatterlist
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> > @@ -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
> sg->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.

dma_get_sgtable goes to ops->get_sgtable first, which dma_to_pfn
will return valid address.
IMHO, Only If ops->alloc returns direct mapping address,
dma_common_get_sgtable can be used.

int arm_dma_get_sgtable(struct device *dev, struct sg_table *sgt,
void *cpu_addr, dma_addr_t handle, size_t size,
struct dma_attrs *attrs)
{
struct page *page = pfn_to_page(dma_to_pfn(dev, handle));
int ret;


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