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Date: Wed, 11 Nov 2015 12:29:18 +1000 From: Dave Airlie <airlied@...il.com> To: Andrew Morton <akpm@...ux-foundation.org> Cc: Alexandre Courbot <acourbot@...dia.com>, Dave Airlie <airlied@...ux.ie>, Ben Skeggs <bskeggs@...hat.com>, Guenter Roeck <linux@...ck-us.net>, Stephen Rothwell <sfr@...b.auug.org.au>, linux-next <linux-next@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>, Alexandre Courbot <gnurou@...il.com> Subject: Re: [PATCH] instmem/gk20a: do not use non-portable dma_to_phys() On 11 November 2015 at 08:41, Andrew Morton <akpm@...ux-foundation.org> wrote: > On Tue, 10 Nov 2015 14:10:47 +0900 Alexandre Courbot <acourbot@...dia.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? > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@...r.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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