Messages in this thread |  | | Subject | Re: [PATCH] drm/tinydrm: mipi-dbi: Fix unbalanced DMA access | From | David Lechner <> | Date | Mon, 7 Aug 2017 13:00:28 -0500 |
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On 08/04/2017 01:49 AM, Noralf Trønnes wrote: > > Den 04.08.2017 00.41, skrev David Lechner: >> 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 <david@lechnology.com> >>> --- >>> 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? > > mipi_dbi_buf_copy() can be used by other rgb565 controllers, hence > the format check I think. So when that happens, it can be moved to > tinydrm-helpers. > > Currently it's not possible to get an illegal format, since mipi-dbi > only supports those two formats. > Userspace can't set an illegal format, beacuse it's checked: > drm_atomic_commit -> drm_atomic_check_only -> drm_atomic_plane_check -> > drm_plane_check_pixel_format > > So I think we can just leave this alone, or put the check before > import_attach if you really want to put this straight. >
I guess we can just leave it alone for now.
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