On Tue Aug 18 20:43:22 2026 +0530, Vishnu Reddy wrote:
> The VPU issues DMA through several SMMU streams, and the hardware does
> not give every stream the same addressable range. The non-pixel stream
> cannot address the low 600MB of IOVA space, while the pixel stream can
> address the full range:
> +-----------------------------------------------------------+
> | non-pixel stream addressable range (600 MB - 3.5 GB) |
> | 0x25800000 - 0xe0000000 |
> +-----------------------------------------------------------+
> | pixel stream addressable range (0 - 3.5 GB) |
> | 0x00000000 - 0xe0000000 |
> +-----------------------------------------------------------+
>
> A single "iommus" property on the video-codec node puts every stream
> in one IOMMU domain sharing one IOVA space, so nothing stops a
> non-pixel buffer from landing below 600MB. Once an allocation lands
> below that boundary the hardware faults, which shows up as unhandled
> SMMU page faults and spontaneous reboots.
> https://gitlab.freedesktop.org/drm/msm/-/work_items/100
>
> Fix this by reserving the 0-600MB range, below the boundary the
> non-pixel stream cannot address, using dma_iova_try_alloc() so the
> IOMMU-DMA core never hands that range out to a real DMA mapping. This
> reserves only IOVA space, it does not allocate any physical memory.
>
> Since sub-nodes for non-pixel, pixel, and secure streams do not exist
> yet and only a single device is available, the restriction is applied
> to both non-pixel and pixel stream IDs.
>
> Fixes: d7378f84e94e ("media: iris: introduce iris core state management with
> shared queues")
> Cc: [email protected]
> Reviewed-by: Vikash Garodia <[email protected]>
> Reviewed-by: Dmitry Baryshkov <[email protected]>
> Signed-off-by: Vishnu Reddy <[email protected]>
> Signed-off-by: Bryan O'Donoghue <[email protected]>
Patch committed.
Thanks,
Bryan O'Donoghue
drivers/media/platform/qcom/iris/iris_core.h | 6 +++
drivers/media/platform/qcom/iris/iris_probe.c | 62 ++++++++++++++++++++++++++-
2 files changed, 67 insertions(+), 1 deletion(-)
---
diff --git a/drivers/media/platform/qcom/iris/iris_core.h
b/drivers/media/platform/qcom/iris/iris_core.h
index 24da60448cf2..3e4cf652bf39 100644
--- a/drivers/media/platform/qcom/iris/iris_core.h
+++ b/drivers/media/platform/qcom/iris/iris_core.h
@@ -7,6 +7,7 @@
#define __IRIS_CORE_H__
#include <linux/types.h>
+#include <linux/dma-mapping.h>
#include <linux/pm_domain.h>
#include <media/v4l2-device.h>
@@ -25,6 +26,9 @@ struct icc_info {
#define IRIS_FW_VERSION_LENGTH 128
#define IFACEQ_CORE_PKT_SIZE (1024 * 4)
+#define IRIS_NP_RESERVE_IOVA_START 0x0
+#define IRIS_NP_RESERVE_IOVA_SIZE 0x25800000
+
enum domain_type {
ENCODER = BIT(0),
DECODER = BIT(1),
@@ -77,6 +81,7 @@ struct qcom_ubwc_cfg_data;
* @instances: a list_head of all instances
* @inst_fw_caps_dec: an array of supported instance capabilities by decoder
* @inst_fw_caps_enc: an array of supported instance capabilities by encoder
+ * @iova_state: a pointer to an array of dma_iova_state entries reserved for
restricted IOVA region
*/
struct iris_core {
@@ -123,6 +128,7 @@ struct iris_core {
/* encoder and decoder have overlapping caps, so two different arrays
are required */
struct platform_inst_fw_cap
inst_fw_caps_dec[INST_FW_CAP_MAX];
struct platform_inst_fw_cap
inst_fw_caps_enc[INST_FW_CAP_MAX];
+ struct dma_iova_state *iova_state;
};
int iris_core_init(struct iris_core *core);
diff --git a/drivers/media/platform/qcom/iris/iris_probe.c
b/drivers/media/platform/qcom/iris/iris_probe.c
index e4acf4a74f94..6581a969fe3f 100644
--- a/drivers/media/platform/qcom/iris/iris_probe.c
+++ b/drivers/media/platform/qcom/iris/iris_probe.c
@@ -150,6 +150,57 @@ static int iris_init_resources(struct iris_core *core)
return iris_init_resets(core);
}
+static void iris_unreserve_iova_region(struct device *dev, struct
dma_iova_state *iova_state)
+{
+ unsigned int i;
+
+ for (i = 0; dma_iova_size(&iova_state[i]); i++)
+ dma_iova_free(dev, &iova_state[i]);
+}
+
+static int iris_reserve_iova_region(struct device *dev, struct dma_iova_state
**iova_state,
+ unsigned long start, unsigned long size)
+{
+ unsigned long dma_limit = dev->bus_dma_limit;
+ unsigned long end, rem, chunk;
+ struct dma_iova_state *state;
+ unsigned int count = 0;
+ int ret = -ENOMEM;
+
+ state = devm_kcalloc(dev, BITS_PER_TYPE(dma_addr_t) + 1,
sizeof(*state), GFP_KERNEL);
+ if (!state)
+ return ret;
+
+ end = start + size;
+ rem = end - max(start, PAGE_SIZE);
+ dev->bus_dma_limit = end - 1;
+
+ while (rem) {
+ chunk = min(end & -end, (u64)1 << (fls64(rem) - 1));
+
+ if (!dma_iova_try_alloc(dev, &state[count], 0, chunk))
+ goto err_free_iova;
+
+ if (state[count].addr != end - chunk || state[count].__size !=
chunk)
+ goto err_free_iova;
+
+ rem -= chunk;
+ end -= chunk;
+ count++;
+ }
+
+ *iova_state = state;
+ dev->bus_dma_limit = dma_limit;
+
+ return 0;
+
+err_free_iova:
+ iris_unreserve_iova_region(dev, state);
+ dev->bus_dma_limit = dma_limit;
+
+ return ret;
+}
+
static int iris_register_video_device(struct iris_core *core, enum domain_type
type)
{
struct video_device *vdev;
@@ -207,6 +258,8 @@ static void iris_remove(struct platform_device *pdev)
v4l2_device_unregister(&core->v4l2_dev);
+ iris_unreserve_iova_region(core->dev, core->iova_state);
+
mutex_destroy(&core->lock);
}
@@ -269,10 +322,15 @@ static int iris_probe(struct platform_device *pdev)
if (ret)
return ret;
- ret = v4l2_device_register(dev, &core->v4l2_dev);
+ ret = iris_reserve_iova_region(dev, &core->iova_state,
IRIS_NP_RESERVE_IOVA_START,
+ IRIS_NP_RESERVE_IOVA_SIZE);
if (ret)
return ret;
+ ret = v4l2_device_register(dev, &core->v4l2_dev);
+ if (ret)
+ goto err_unresv_iova_region;
+
ret = iris_register_video_device(core, DECODER);
if (ret)
goto err_v4l2_unreg;
@@ -306,6 +364,8 @@ err_vdev_unreg_dec:
video_unregister_device(core->vdev_dec);
err_v4l2_unreg:
v4l2_device_unregister(&core->v4l2_dev);
+err_unresv_iova_region:
+ iris_unreserve_iova_region(dev, core->iova_state);
return ret;
}
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