24.10.2019 16:47, Thierry Reding пишет: > On Thu, Oct 24, 2019 at 04:35:13PM +0300, Dmitry Osipenko wrote: >> 24.10.2019 14:50, Thierry Reding пишет: >>> On Sun, Jun 23, 2019 at 08:37:41PM +0300, Dmitry Osipenko wrote: >>>> On ARM32 we don't want any of the clients device to be backed by the >>>> implicit domain, simply because we can't afford such a waste on older >>>> Tegra SoCs that have very few domains available in total. The recent IOMMU >>>> support addition for the Video Decoder hardware uncovered the problem >>>> that an unfortunate drivers probe order results in the DRM driver probe >>>> failure if CONFIG_ARM_DMA_USE_IOMMU=y due to a shortage of IOMMU domains >>>> caused by the implicit backing. The host1x_client_register() is a common >>>> function that is invoked by all of the relevant DRM drivers during theirs >>>> probe and hence it is convenient to remove the implicit backing there, >>>> resolving the problem. >>>> >>>> Signed-off-by: Dmitry Osipenko <digetx@xxxxxxxxx> >>>> --- >>>> drivers/gpu/host1x/bus.c | 19 +++++++++++++++++++ >>>> 1 file changed, 19 insertions(+) >>> >>> I don't really want to do this in a central place like this. If we >>> really do need this, why can't we do it in the individual drivers? >> >> Why do you want to duplicate the same action for each driver instead of >> doing it in a single common place? > > I don't mind doing it in a common place in particular, I just don't want > to do this within the host1x bus infrastructure. This is really a policy > decision that should be up to drivers. Consider the case where we had a > different host1x driver (for V4L2 for example) that would actually want > to use the DMA API. In that case we may want to detach in the DRM driver > but not the V4L2 driver. Okay.
