From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from lb3-smtp-cloud3.xs4all.net ([194.109.24.30]:35661 "EHLO lb3-smtp-cloud3.xs4all.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751103AbcD0MKn (ORCPT ); Wed, 27 Apr 2016 08:10:43 -0400 Subject: Re: [PATCH RESEND 1/2] media: vb2-dma-contig: add helper for setting dma max seg size To: Marek Szyprowski , linux-media@vger.kernel.org, linux-samsung-soc@vger.kernel.org References: <1461758429-12913-1-git-send-email-m.szyprowski@samsung.com> Cc: Sylwester Nawrocki , Kamil Debski , Laurent Pinchart , Krzysztof Kozlowski , Bartlomiej Zolnierkiewicz From: Hans Verkuil Message-ID: <5720AC3C.8090101@xs4all.nl> Date: Wed, 27 Apr 2016 14:10:36 +0200 MIME-Version: 1.0 In-Reply-To: <1461758429-12913-1-git-send-email-m.szyprowski@samsung.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-media-owner@vger.kernel.org List-ID: On 04/27/2016 02:00 PM, Marek Szyprowski wrote: > Add a helper function for device drivers to set DMA's max_seg_size. > Setting it to largest possible value lets DMA-mapping API always create > contiguous mappings in DMA address space. This is essential for all > devices, which use dma-contig videobuf2 memory allocator and shared > buffers. > > Signed-off-by: Marek Szyprowski > --- > This patch was posted earlier as a part of > http://thread.gmane.org/gmane.linux.drivers.video-input-infrastructure/97316 > thread, but applying it is really needed to get all Exynos multimedia > drivers working with IOMMU enabled. > > Best regards, > Marek Szyprowski > --- > drivers/media/v4l2-core/videobuf2-dma-contig.c | 15 +++++++++++++++ > include/media/videobuf2-dma-contig.h | 1 + > 2 files changed, 16 insertions(+) > > diff --git a/drivers/media/v4l2-core/videobuf2-dma-contig.c b/drivers/media/v4l2-core/videobuf2-dma-contig.c > index 5361197..f611456 100644 > --- a/drivers/media/v4l2-core/videobuf2-dma-contig.c > +++ b/drivers/media/v4l2-core/videobuf2-dma-contig.c > @@ -753,6 +753,21 @@ void vb2_dma_contig_cleanup_ctx(void *alloc_ctx) > } > EXPORT_SYMBOL_GPL(vb2_dma_contig_cleanup_ctx); > > +int vb2_dma_contig_set_max_seg_size(struct device *dev, unsigned int size) > +{ > + if (!dev->dma_parms) { > + dev->dma_parms = devm_kzalloc(dev, sizeof(dev->dma_parms), > + GFP_KERNEL); The v3 patch from December uses kzalloc here. Is this perhaps on old version? > + if (!dev->dma_parms) > + return -ENOMEM; > + } > + if (dma_get_max_seg_size(dev) < size) > + return dma_set_max_seg_size(dev, size); > + > + return 0; > +} > +EXPORT_SYMBOL_GPL(vb2_dma_contig_set_max_seg_size); Admittedly I haven't looked closely at this, but is this something that you want for all dma-contig devices? Or to rephrase this question: what type of devices will need this? Regards, Hans > + > MODULE_DESCRIPTION("DMA-contig memory handling routines for videobuf2"); > MODULE_AUTHOR("Pawel Osciak "); > MODULE_LICENSE("GPL"); > diff --git a/include/media/videobuf2-dma-contig.h b/include/media/videobuf2-dma-contig.h > index 2087c9a..98857b5 100644 > --- a/include/media/videobuf2-dma-contig.h > +++ b/include/media/videobuf2-dma-contig.h > @@ -35,6 +35,7 @@ static inline void *vb2_dma_contig_init_ctx(struct device *dev) > } > > void vb2_dma_contig_cleanup_ctx(void *alloc_ctx); > +int vb2_dma_contig_set_max_seg_size(struct device *dev, unsigned int size); > > extern const struct vb2_mem_ops vb2_dma_contig_memops; > >