On Thu, Feb 20, 2020 at 05:21:35PM +0000, Robin Murphy wrote:
>> @@ -196,10 +192,15 @@ void *dma_direct_alloc_pages(struct device *dev, size_t size,
>> memset(ret, 0, size);
>> - if (IS_ENABLED(CONFIG_ARCH_HAS_UNCACHED_SEGMENT) &&
>> - dma_alloc_need_uncached(dev, attrs)) {
>> + if (dma_alloc_need_uncached(dev, attrs)) {
>> arch_dma_prep_coherent(page, size);
>> - ret = uncached_kernel_address(ret);
>> +
>> + if (IS_ENABLED(CONFIG_ARCH_HAS_DMA_SET_UNCACHED)) {
>> + if (!arch_dma_set_uncached(ret, size))
>> + goto out_free_pages;
>> + } else if (IS_ENABLED(CONFIG_ARCH_HAS_UNCACHED_SEGMENT)) {
>> + ret = uncached_kernel_address(ret);
>
> Hmm, would we actually need to keep ARCH_HAS_UNCACHED_SEGMENT? If
> arch_dma_set_uncached() returned void*/ERR_PTR instead, then it could work
> for both cases (with arch_dma_clear_uncached() being a no-op for segments).
Yes, I think so. I was a little worried about what to do with
cached_kernel_address() in that scheme, but it turns out with the recent
round of dma-direct cleanup that is actually entirely unused now.
