Re: [PATCH 11/18] iommu/omap: Add IOMMU_DOMAIN_DMA support

Suman Anna
2020-08-24T21:41:00Z

Hi Robin,

On 8/20/20 10:08 AM, Robin Murphy wrote:
> Now that arch/arm is wired up for default domains and iommu-dma,
> implement the corresponding driver-side support for DMA domains.
>
> Signed-off-by: Robin Murphy <robin.murphy@arm.com>
> ---
> drivers/iommu/omap-iommu.c | 22 +++++++++++++++++++++-
> 1 file changed, 21 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/iommu/omap-iommu.c b/drivers/iommu/omap-iommu.c
> index 71f29c0927fc..ea25c2fe0418 100644
> --- a/drivers/iommu/omap-iommu.c
> +++ b/drivers/iommu/omap-iommu.c
> @@ -9,6 +9,7 @@
> * Paul Mundt and Toshihiro Kobayashi
> */
>
> +#include <linux/dma-iommu.h>
> #include <linux/dma-mapping.h>
> #include <linux/err.h>
> #include <linux/slab.h>
> @@ -1574,13 +1575,19 @@ static struct iommu_domain *omap_iommu_domain_alloc(unsigned type)
> {
> struct omap_iommu_domain *omap_domain;
>
> - if (type != IOMMU_DOMAIN_UNMANAGED)
> + if (type != IOMMU_DOMAIN_UNMANAGED && type != IOMMU_DOMAIN_DMA)
> return NULL;
>
> omap_domain = kzalloc(sizeof(*omap_domain), GFP_KERNEL);
> if (!omap_domain)
> return NULL;
>
> + if (type == IOMMU_DOMAIN_DMA &&
> + iommu_get_dma_cookie(&omap_domain->domain)) {
> + kfree(omap_domain);
> + return NULL;
> + }
> +
> spin_lock_init(&omap_domain->lock);
>
> omap_domain->domain.geometry.aperture_start = 0;
> @@ -1601,6 +1608,7 @@ static void omap_iommu_domain_free(struct iommu_domain *domain)
> if (omap_domain->dev)
> _omap_iommu_detach_dev(omap_domain, omap_domain->dev);
>
> + iommu_put_dma_cookie(&omap_domain->domain);
> kfree(omap_domain);
> }
>
> @@ -1736,6 +1744,17 @@ static struct iommu_group *omap_iommu_device_group(struct device *dev)
> return group;
> }
>
> +static int omap_iommu_of_xlate(struct device *dev,
> + struct of_phandle_args *args)
> +{
> + /*
> + * Logically, some of the housekeeping from _omap_iommu_add_device()
> + * should probably move here, but the minimum we *need* is simply to
> + * cooperate with of_iommu at all to let iommu-dma work.
> + */
> + return 0;
> +}
> +

I have tested this series, and it is breaking the OMAP remoteproc functionality.
We definitely need some more plumbing. I am currently getting MMU faults and
also the DMA allocated addresses are not coming from the device-specific CMA
pools (opposite of what Sakari has reported with OMAP3 ISP). Just removing the
of_xlate gets me back the expected allocations, and no MMU faults, but I don't
see any valid traces.

The MMU devices that the OMAP IOMMU driver deals with are not traditional
bus-level IOMMU devices, but local MMU devices that are present within a remote
processor sub-system or hardware accelerator (eg: OMAP3 ISP). The usage is also
slightly different between remoteprocs and OMAP3 ISP. The former uses the CMA
pools and iommu_map/unmap API (UNMANAGED iommu domain), as the allocated regions
need to be mapped using specific device addresses adhering to the firmware
linker map, while OMAP3 ISP uses it like a traditional DMA pool.

regards
Suman

> static const struct iommu_ops omap_iommu_ops = {
> .domain_alloc = omap_iommu_domain_alloc,
> .domain_free = omap_iommu_domain_free,
> @@ -1747,6 +1766,7 @@ static const struct iommu_ops omap_iommu_ops = {
> .probe_device = omap_iommu_probe_device,
> .release_device = omap_iommu_release_device,
> .device_group = omap_iommu_device_group,
> + .of_xlate = omap_iommu_of_xlate,
> .pgsize_bitmap = OMAP_IOMMU_PGSIZES,
> };
>
>