Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755331AbbFRK7U (ORCPT ); Thu, 18 Jun 2015 06:59:20 -0400 Received: from pandora.arm.linux.org.uk ([78.32.30.218]:39806 "EHLO pandora.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754987AbbFRK5d (ORCPT ); Thu, 18 Jun 2015 06:57:33 -0400 Date: Thu, 18 Jun 2015 11:57:15 +0100 From: Russell King - ARM Linux To: Mark Yao Cc: dri-devel@lists.freedesktop.org, zwl@rock-chips.com, Daniel Vetter , David Airlie , linux-kernel@vger.kernel.org, Daniel Kurtz , tfiga@chromium.org, linux-rockchip@lists.infradead.org, Rob Clark , Philipp Zabel , xw@rock-chips.com, dkm@rock-chips.com, sandy.huang@rock-chips.com, linux-arm-kernel@lists.infradead.org, Heiko Stuebner Subject: Re: [PATCH 1/6] drm/rockchip: import dma_buf to gem Message-ID: <20150618105715.GJ7557@n2100.arm.linux.org.uk> References: <1434613770-6608-1-git-send-email-mark.yao@rock-chips.com> <1434613770-6608-2-git-send-email-mark.yao@rock-chips.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1434613770-6608-2-git-send-email-mark.yao@rock-chips.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3843 Lines: 94 On Thu, Jun 18, 2015 at 03:49:25PM +0800, Mark Yao wrote: > We want to display a buffer allocated by other driver, need import > the buffer to gem. > > Signed-off-by: Mark Yao > --- > drivers/gpu/drm/rockchip/rockchip_drm_drv.c | 1 + > drivers/gpu/drm/rockchip/rockchip_drm_gem.c | 45 +++++++++++++++++++++++++-- > drivers/gpu/drm/rockchip/rockchip_drm_gem.h | 5 ++- > 3 files changed, 47 insertions(+), 4 deletions(-) > > diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_drv.c b/drivers/gpu/drm/rockchip/rockchip_drm_drv.c > index 3962176..9001a90 100644 > --- a/drivers/gpu/drm/rockchip/rockchip_drm_drv.c > +++ b/drivers/gpu/drm/rockchip/rockchip_drm_drv.c > @@ -287,6 +287,7 @@ static struct drm_driver rockchip_drm_driver = { > .prime_handle_to_fd = drm_gem_prime_handle_to_fd, > .prime_fd_to_handle = drm_gem_prime_fd_to_handle, > .gem_prime_import = drm_gem_prime_import, > + .gem_prime_import_sg_table = rockchip_gem_prime_import_sg_table, > .gem_prime_export = drm_gem_prime_export, > .gem_prime_get_sg_table = rockchip_gem_prime_get_sg_table, > .gem_prime_vmap = rockchip_gem_prime_vmap, > diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_gem.c b/drivers/gpu/drm/rockchip/rockchip_drm_gem.c > index eb2282c..2e30e23 100644 > --- a/drivers/gpu/drm/rockchip/rockchip_drm_gem.c > +++ b/drivers/gpu/drm/rockchip/rockchip_drm_gem.c > @@ -18,6 +18,7 @@ > #include > > #include > +#include > > #include "rockchip_drm_drv.h" > #include "rockchip_drm_gem.h" > @@ -105,6 +106,38 @@ int rockchip_gem_mmap(struct file *filp, struct vm_area_struct *vma) > return ret; > } > > +struct drm_gem_object * > +rockchip_gem_prime_import_sg_table(struct drm_device *drm, > + struct dma_buf_attachment *attach, > + struct sg_table *sgt) > +{ > + struct rockchip_gem_object *rk_obj; > + struct drm_gem_object *obj; > + int ret; > + > + rk_obj = kzalloc(sizeof(*rk_obj), GFP_KERNEL); > + if (!rk_obj) > + return ERR_PTR(-ENOMEM); > + > + obj = &rk_obj->base; > + > + drm_gem_private_object_init(drm, obj, attach->dmabuf->size); > + > + if (!dma_map_sg(drm->dev, sgt->sgl, sgt->nents, DMA_TO_DEVICE)) { > + ret = -ENOMEM; > + goto err_free_obj; > + } > + rk_obj->dma_addr = sg_dma_address(sgt->sgl); > + rk_obj->sgt = sgt; > + obj->size = sg_dma_len(sgt->sgl); This is wrong. First, if you can only cope with a single scatterlist entry, you need to enforce that. You can do that in your gem_prime_import_sg_table() method by checking sgt->nents. Secondly, you're mapping an already mapped scatterlist - scatterlists are mapped by the exporter inside dma_buf_map_attachment() for your device. Thirdly, I hate drm_gem_prime_import() being used on ARM... it forces drivers to do something very buggy: the DMA buffer is mapped for DMA when the buffer is imported. If the buffer is a write-combine or cached buffer, writes to the buffer after the import will not become visible to the display hardware until sometime later (when they're evicted from the caches and/or pushed out of the bus structure.) The DMA mapping should be performed as close to the start of DMA as possible. However, this is a long-standing issue I have with dma_buf itself and is not something you should be too concerned with in your patch. Just bear it in mind if you start to see corruption of imported buffers - the answer is not more dma_map_sg() calls, but to get dma_buf fixed. -- FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up according to speedtest.net. -- 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/