Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751994AbbKKC3W (ORCPT ); Tue, 10 Nov 2015 21:29:22 -0500 Received: from mail-lf0-f44.google.com ([209.85.215.44]:33582 "EHLO mail-lf0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751621AbbKKC3U (ORCPT ); Tue, 10 Nov 2015 21:29:20 -0500 MIME-Version: 1.0 In-Reply-To: <20151110144144.39c2a4109c26e91f4f3fb47b@linux-foundation.org> References: <1447132247-9767-1-git-send-email-acourbot@nvidia.com> <20151110144144.39c2a4109c26e91f4f3fb47b@linux-foundation.org> Date: Wed, 11 Nov 2015 12:29:18 +1000 Message-ID: Subject: Re: [PATCH] instmem/gk20a: do not use non-portable dma_to_phys() From: Dave Airlie To: Andrew Morton Cc: Alexandre Courbot , Dave Airlie , Ben Skeggs , Guenter Roeck , Stephen Rothwell , linux-next , LKML , Alexandre Courbot Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2344 Lines: 55 On 11 November 2015 at 08:41, Andrew Morton wrote: > On Tue, 10 Nov 2015 14:10:47 +0900 Alexandre Courbot 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@vger.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@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/