Hi, 2017-07-17 10:43 GMT+08:00 Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>: > Hi Jacob, > > On Sunday 16 Jul 2017 12:19:41 Jacob Chen wrote: >> 2017-07-16 0:49 GMT+08:00 Personnel: >> > Le samedi 15 juillet 2017 à 12:42 +0300, Laurent Pinchart a écrit : >> >> On Saturday 15 Jul 2017 14:58:36 Jacob Chen wrote: >> >> > Rockchip RGA is a separate 2D raster graphic acceleration unit. It >> >> > accelerates 2D graphics operations, such as point/line drawing, image >> >> > scaling, rotation, BitBLT, alpha blending and image blur/sharpness. >> >> > >> >> > The drvier is mostly based on s5p-g2d v4l2 m2m driver. >> >> > And supports various operations from the rendering pipeline. >> >> > >> >> > - copy >> >> > - fast solid color fill >> >> > - rotation >> >> > - flip >> >> > - alpha blending >> >> >> >> I notice that you don't support the drawing operations. How do you plan >> >> to support them later through the V4L2 M2M API ? I hate stating the >> >> obvious, but wouldn't the DRM API be better fit for a graphic accelerator >> >> ? >> > >> > It could fit, maybe, but it really lacks some framework. Also, DRM is >> > not really meant for M2M operation, and it's also not great for multi- >> > process. Until recently, there was competing drivers for Exynos, both >> > implemented in V4L2 and DRM, for similar rational, all DRM ones are >> > being deprecated/removed. >> > >> > I think 2D blitters in V4L2 are fine, but they terribly lack something >> > to differentiate them from converters/scalers when looking up the HW >> > list. Could be as simple as a capability flag, if I can suggest. For >> > the reference, the 2D blitter on IMX6 has been used to implement a live >> > video mixer in GStreamer. >> > >> > https://bugzilla.gnome.org/show_bug.cgi?id=772766 >> >> We have write a drm RGA driver. >> https://patchwork.kernel.org/patch/8630841/ >> >> Here are the reasons that why i rewrite it to V4l2 M2M. >> 1. V4l2 have a better buffer framework. If it use DRM-GEM to handle buffers, >> there will be much redundant cache flush, and we have to add much hack code >> to workaround. > > I'm glad to hear that you find buffer handling easy in V4L2 :-) > >> 2. This driver will be used in rockchip linux project. We mostly use it to >> scale/colorconvert/rotate/mix video/camera stream. >> A V4L2 M2M drvier can be directly used in gstreamer. >> >> The disadvantages of V4l2 M2M API is that it's not stateless. >> It's inconvenient if user change size frequently, but it's OK, >> we have not yet need this and I think it's possible to extend. ;) > > CC'ing Alexandre Courbot. Alex, how's the request API going ? :-) > >> >> Additionally, V4L2 M2M has one source and one destination. How do you >> >> implement alpha blending in that case, which by definition requires at >> >> least two sources ? >> > >> > This type of HW only do in-place blits. When using such a node, the >> > buffer queued on the V4L2_CAPTURE contains the destination image, and >> > the buffer queued on the V4L2_OUTPUT is the source image. >> >> Yep. > > So the device performs bi-directional DMA on the capture queue buffers ? > Interesting, does videobuf2 support that properly ? > >From the code, I think V4L2_CAPTURE and V4L2_OUTPUT are handled in the same way. In my test, it work properly. >> >>> The code in rga-hw.c is used to configure regs accroding to operations. >> >>> >> >>> The code in rga-buf.c is used to create private mmu table for RGA. >> >>> The tables is stored in a list, and be removed when buffer is cleanup. >> >> >> >> Looking at the implementation it seems to be a scatter-gather list, not >> >> an MMU. Is that right ? Does the hardware documentation refer to it as an >> >> MMU ? >> >> It's a 1-level MMU... We use it like a scatter-gather list, >> It's also the reason why we don't use RGA with DRM API. > > You might want to explain this in the code, otherwise someone will ask you why > you don't implement support for the MMU through the IOMMU API. Calling it > scatter-gather would solve that problem, but if the hardware manual calls it > an MMU, there's no reason not to use that name in the code. > ok, i will add comments >> >>> Signed-off-by: Jacob Chen <jacob-chen@xxxxxxxxxx> >> >>> --- >> >>> >> >>> drivers/media/platform/Kconfig | 11 + >> >>> drivers/media/platform/Makefile | 2 + >> >>> drivers/media/platform/rockchip-rga/Makefile | 3 + >> >>> drivers/media/platform/rockchip-rga/rga-buf.c | 122 ++++ >> >>> drivers/media/platform/rockchip-rga/rga-hw.c | 652 ++++++++++++++++++ >> >>> drivers/media/platform/rockchip-rga/rga-hw.h | 437 ++++++++++++ >> >>> drivers/media/platform/rockchip-rga/rga.c | 958 ++++++++++++++++++ >> >>> drivers/media/platform/rockchip-rga/rga.h | 111 +++ >> >>> 8 files changed, 2296 insertions(+) >> >>> create mode 100644 drivers/media/platform/rockchip-rga/Makefile >> >>> create mode 100644 drivers/media/platform/rockchip-rga/rga-buf.c >> >>> create mode 100644 drivers/media/platform/rockchip-rga/rga-hw.c >> >>> create mode 100644 drivers/media/platform/rockchip-rga/rga-hw.h >> >>> create mode 100644 drivers/media/platform/rockchip-rga/rga.c >> >>> create mode 100644 drivers/media/platform/rockchip-rga/rga.h > > -- > Regards, > > Laurent Pinchart >
