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@gmail.com
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? Also, we already call host1x_client_iommu_attach() from all the drivers and that detaches from the IOMMU as well. So I'm not sure I understand why this is needed.
Thierry
diff --git a/drivers/gpu/host1x/bus.c b/drivers/gpu/host1x/bus.c index 742aa9ff21b8..559df3974afb 100644 --- a/drivers/gpu/host1x/bus.c +++ b/drivers/gpu/host1x/bus.c @@ -14,6 +14,10 @@ #include "bus.h" #include "dev.h"
+#if IS_ENABLED(CONFIG_ARM_DMA_USE_IOMMU) +#include <asm/dma-iommu.h> +#endif
static DEFINE_MUTEX(clients_lock); static LIST_HEAD(clients);
@@ -710,6 +714,21 @@ int host1x_client_register(struct host1x_client *client) struct host1x *host1x; int err;
+#if IS_ENABLED(CONFIG_ARM_DMA_USE_IOMMU)
- /*
* The client's driver could be backed by implicit IOMMU mapping* and we don't want to have that because all of current Tegra* drivers are managing IOMMU by themselves. This is a convenient* place for unmapping of the implicit mapping because this function* is called by all host1x drivers during theirs probe.*/- if (client->dev->archdata.mapping) {
struct dma_iommu_mapping *mapping =to_dma_iommu_mapping(client->dev);arm_iommu_detach_device(client->dev);arm_iommu_release_mapping(mapping);- }
+#endif mutex_lock(&devices_lock);
list_for_each_entry(host1x, &devices, list) {
2.22.0