Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754825Ab2KBVIR (ORCPT ); Fri, 2 Nov 2012 17:08:17 -0400 Received: from g6t0184.atlanta.hp.com ([15.193.32.61]:6186 "EHLO g6t0184.atlanta.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752502Ab2KBVIQ (ORCPT ); Fri, 2 Nov 2012 17:08:16 -0400 Message-ID: <1351890491.3161.23.camel@lorien2> Subject: Re: [PATCH RFT RESEND linux-next] c6x: dma-mapping: support debug_dma_mapping_error From: Shuah Khan Reply-To: shuah.khan@hp.com To: Mark Salter Cc: Andrew Morton , a-jacquiot@ti.com, linux-c6x-dev@linux-c6x.org, LKML , shuahkhan@gmail.com Date: Fri, 02 Nov 2012 15:08:11 -0600 In-Reply-To: <1351889957.15973.43.camel@deneb.redhat.com> References: <1351206082.6851.6.camel@lorien2> <1351266055.4013.1.camel@lorien2> <1351874655.2721.16.camel@lorien2> <1351883445.15973.24.camel@deneb.redhat.com> <1351885999.3161.11.camel@lorien2> <1351887326.15973.35.camel@deneb.redhat.com> <1351887967.3161.17.camel@lorien2> <1351889957.15973.43.camel@deneb.redhat.com> Organization: ISS-Linux Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.3-0ubuntu6 Content-Transfer-Encoding: 7bit Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4613 Lines: 104 On Fri, 2012-11-02 at 16:59 -0400, Mark Salter wrote: > On Fri, 2012-11-02 at 14:26 -0600, Shuah Khan wrote: > > On Fri, 2012-11-02 at 16:15 -0400, Mark Salter wrote: > > > On Fri, 2012-11-02 at 13:53 -0600, Shuah Khan wrote: > > > > On Fri, 2012-11-02 at 15:10 -0400, Mark Salter wrote: > > > > > On Fri, 2012-11-02 at 10:44 -0600, Shuah Khan wrote: > > > > > > On Fri, 2012-10-26 at 09:40 -0600, Shuah Khan wrote: > > > > > > > Add support for debug_dma_mapping_error() call to avoid warning from > > > > > > > debug_dma_unmap() interface when it checks for mapping error checked > > > > > > > status. Without this patch, device driver failed to check map error > > > > > > > warning is generated. > > > > > > > > > > > > > > Signed-off-by: Shuah Khan > > > > > > > --- > > > > > > > arch/c6x/include/asm/dma-mapping.h | 1 + > > > > > > > 1 file changed, 1 insertion(+) > > > > > > > > > > > Would you like to this patch go through c6x arch tree or linux-next? > > > > > > Please let me know your preference. > > > > > > > > > > I tried to test this but I get a build error with CONFIG_DMA_API_DEBUG: > > > > > > > > > > /linux-next/lib/dma-debug.c: In function 'has_mapping_error': > > > > > /linux-next/lib/dma-debug.c:863:15: error: implicit declaration of function 'get_dma_ops' [-Werror=implicit-function-declaration] > > > > > /linux-next/lib/dma-debug.c:863:34: warning: initialization makes pointer from integer without a cast [enabled by default] > > > > > > > > > > C6X (along with some other architectures) doesn't have a get_dma_ops() > > > > > function defined. > > > > > > > > That is a problem I didn't think about. I did a check and looks like c6x > > > > and frv are the only ones that don't have get_dma_ops() defined. frv is > > > > > > By my count, there are 14 architectures with get_dma_ops() and 14 > > > without. > > Right. I should have explained more. The following archs > > > > arch/avr32/include/asm/dma-mapping.h > > arch/blackfin/include/asm/dma-mapping.h > > arch/cris/include/asm/dma-mapping.h > > arch/mn10300/include/asm/dma-mapping.h > > arch/parisc/include/asm/dma-mapping.h > > arch/xtensa/include/asm/dma-mapping.h > > > > define dma_map_page() and dma_map_single() and not call > > debug_dma_map_page() interface. There is no risk of mis-matched debug > > and non-debug mapping and mapping error checks like in the case of other > > archs and c6x. > > Ah, okay. Not all architectures support HAVE_DMA_API_DEBUG. So, of those > that do, c6x seems to be the only one with dma_ops. > > > > > > > in a different category as it doesn't use dma_debug interfaces. IN the > > > > case c6x, now with my change to add debug_dma_mapping_error(), we will > > > > start seeing warnings since dma_map_page() and dma_map_single() are > > > > debugged with a call to debug_dma_map_page() and the corresponding > > > > dma_mapping_error() interface doesn't call debug_dma_mapping_error() > > > > interface > > > > > > > > - Does adding get_dma_ops() make sense? Doesn't look like c6x exports > > > > dma_ops? > > > > > > > > Any other ideas? > > > > > > I'm not sure. I don't know what get_dma_ops() does and it doesn't seem > > > to be documented anywhere. > > > > It returns pointer to dma_ops like the one on alpha: > > > > static inline struct dma_map_ops *get_dma_ops(struct device *dev) > > { > > return dma_ops; > > } > > Okay, so what is dma_ops used for? Looks like maybe supporting different > dma features/functionality on different busses/devices. > > > > > c6x doesn't define dma_ops looks like. Is that correct? Returning null > > from get_dma_ops() is not an option as get_dma_ops() return is assumed > > to be not null. > > As things stand, c6x DMA hw doesn't really need dma_ops and until this > patch, I could build in DMA debug support without dma_ops. So do we > really want to require dma_ops for dma debug support even for those > architectures which don't otherwise need it? I could add dma_ops, but > it seems silly to do so only for dma debug. I agree it doesn't make sense to add dma_ops when there is no need to. Until now dma-debug didn't depend on dma_ops. This dependency has been introduced with the debug_dma_mapping_error() interface I added :( Let me go back and see if I can come up with a way to not require dma_ops for debug-dma. Thanks, -- Shuah -- 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/