On 11 November 2015 at 08:41, Andrew Morton <a...@linux-foundation.org> wrote:
> On Tue, 10 Nov 2015 14:10:47 +0900 Alexandre Courbot <acour...@nvidia.com>
> wrote:
>
>> dma_to_phys() is not guaranteed to be available on all platforms and
>> should not be used outside of arch/. Replace it with what it is expected
>> to do in our case: simply cast the DMA handle to a physical address.
>
> mainline i386 allmodconfig is now busted.
I'll push my hack to make things build into drm-fixes while we discuss
the subtlety.
Dave.
>
>> --- a/drivers/gpu/drm/nouveau/nvkm/subdev/instmem/gk20a.c
>> +++ b/drivers/gpu/drm/nouveau/nvkm/subdev/instmem/gk20a.c
>> @@ -134,13 +134,17 @@ static void __iomem *
>> gk20a_instobj_cpu_map_dma(struct nvkm_memory *memory)
>> {
>> struct gk20a_instobj_dma *node = gk20a_instobj_dma(memory);
>> - struct device *dev = node->base.imem->base.subdev.device->dev;
>> int npages = nvkm_memory_size(memory) >> 12;
>> struct page *pages[npages];
>> int i;
>>
>> - /* phys_to_page does not exist on all platforms... */
>> - pages[0] = pfn_to_page(dma_to_phys(dev, node->handle) >> PAGE_SHIFT);
>> + /*
>> + * Ideally we would have a function to translate a handle to a physical
>> + * address, but there is no portable way of doing this. However since
>> we
>> + * always use the DMA API without an IOMMU, we can assume that handles
>> + * are actual physical addresses.
>> + */
>> + pages[0] = pfn_to_page(((phys_addr_t)node->handle) >> PAGE_SHIFT);
>
> This looks ugly.
>
> What's actually going on here? Why is this driver doing something which
> no other driver appears to need to do?
>
> Is it the driver which is broken, or are the core kernel APIs inadequate?
>
> If the latter, what can we do to fix them up?
>
> IOW, how do we fix this properly?
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