Hi, Rob: On Wed, 2019-10-23 at 17:56 -0500, Rob Herring wrote: > On Wed, Oct 23, 2019 at 4:06 PM CK Hu <ck.hu@xxxxxxxxxxxx> wrote: > > > > Hi, Rob: > > > > On Wed, 2019-10-23 at 12:42 -0500, Rob Herring wrote: > > > On Tue, Oct 22, 2019 at 12:07 PM Matthias Brugger > > > <matthias.bgg@xxxxxxxxx> wrote: > > > > > > > > Hi Rob, > > > > > > > > On 21/10/2019 23:45, Rob Herring wrote: > > > > > The only reason the Mediatek driver doesn't use the CMA helpers is it > > > > > sets DMA_ATTR_NO_KERNEL_MAPPING and does a vmap() on demand. Using > > > > > vmap() is not even guaranteed to work as DMA buffers may not have a > > > > > struct page. Now that the CMA helpers support setting > > > > > DMA_ATTR_NO_KERNEL_MAPPING as needed or not, convert Mediatek driver to > > > > > use CMA helpers. > > > > > > > > > > Cc: CK Hu <ck.hu@xxxxxxxxxxxx> > > > > > Cc: Philipp Zabel <p.zabel@xxxxxxxxxxxxxx> > > > > > Cc: David Airlie <airlied@xxxxxxxx> > > > > > Cc: Daniel Vetter <daniel@xxxxxxxx> > > > > > Cc: Matthias Brugger <matthias.bgg@xxxxxxxxx> > > > > > Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx > > > > > Cc: linux-mediatek@xxxxxxxxxxxxxxxxxxx > > > > > Signed-off-by: Rob Herring <robh@xxxxxxxxxx> > > > > > --- > > > > > > > > I tested this on my Chromebook with some patches on top of v5.4-rc1 [1], which > > > > work. If I add your patches on top of that, the system does not boot up. > > > > Unfortunately I don't have a serial console, so I wasn't able to see if there is > > > > any error message. > > > > > > Thanks for testing. I'm based on drm-misc-next, but don't see anything > > > obvious there that would matter. There are some mmap changes, but I > > > think they shouldn't matter. > > > > > > Did you have fbcon enabled? That may give more clues about where the problem is. > > > > There are priv->dma_dev for dma device, but it is not drm device. In > > mt8173.dtsi [1], there are mmsys device and ovl device, mmsys device is > > drm device and ovl device is mmsys's sub device which provide dma > > function, so ovl is the priv->dma_dev. I think your patch directly use > > drm device for dma operation and this would cause dma function fail. > > Please use priv->dma_dev for dma operation. > > Right, thanks for catching that. Either we'll need to make CMA GEM > object have a struct device ptr or adjust the drm_device.dev to have > the necessary DMA setup. > > One question though, why do you use CMA when you have an IOMMU? That's > not optimal as CMA size may be limited. Or you don't always have an > IOMMU? For all upstreamed mediatek SoC, all has IOMMU, so it does not need CMA. I think we use CMA just because we refer to other drm driver to implement mediatek drm driver and we misused CMA helper function but it works. I think we should change to more accurate implementation. If you want, you could modify it in this series. Regards, CK > > Rob _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
