From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Lechner Subject: Re: [PATCH] drm/tinydrm: mipi-dbi: Fix unbalanced DMA access Date: Thu, 3 Aug 2017 17:41:02 -0500 Message-ID: <51efe719-566f-6761-9b39-c4cdfdba7a3c@lechnology.com> References: <1501618466-32191-1-git-send-email-david@lechnology.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1501618466-32191-1-git-send-email-david@lechnology.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: dri-devel@lists.freedesktop.org Cc: =?UTF-8?Q?Noralf_Tr=c3=b8nnes?= , David Airlie , linux-kernel@vger.kernel.org List-Id: dri-devel@lists.freedesktop.org On 08/01/2017 03:14 PM, David Lechner wrote: > If we return here and import_attach is true, then dma_buf_end_cpu_access() > will not be called balance dma_buf_begin_cpu_access(). > > Fix by setting ret instead of returning. > > Signed-off-by: David Lechner > --- > drivers/gpu/drm/tinydrm/mipi-dbi.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/tinydrm/mipi-dbi.c b/drivers/gpu/drm/tinydrm/mipi-dbi.c > index c83eeb7..e10fa4b 100644 > --- a/drivers/gpu/drm/tinydrm/mipi-dbi.c > +++ b/drivers/gpu/drm/tinydrm/mipi-dbi.c > @@ -183,7 +183,8 @@ static int mipi_dbi_buf_copy(void *dst, struct drm_framebuffer *fb, > dev_err_once(fb->dev->dev, "Format is not supported: %s\n", > drm_get_format_name(fb->format->format, > &format_name)); > - return -EINVAL; > + ret = -EINVAL; > + break; > } > > if (import_attach) > I just realized that the next line here can mask ret. if (import_attach) ret = dma_buf_end_cpu_access(import_attach->dmabuf, DMA_FROM_DEVICE); So, we should either ignore the return value from dma_buf_end_cpu_access() always or add some logic to ignore it if ret is already an error. In some of the other patches I have been sending, we have the same situation. I those, I have opted to just ignore the return value from dma_buf_end_cpu_access(). e.g... if (import_attach) dma_buf_end_cpu_access(import_attach->dmabuf, DMA_FROM_DEVICE); Is this a reasonable thing to do?