[PATCH v2 2/2] media: venus: Fix iova allocation from restrict region

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: af2c3834c8ca ("[media] media: venus: adding core part and helper functions")
Cc: [email protected]
Reviewed-by: Vikash Garodia <[email protected]>
Reviewed-by: Dmitry Baryshkov <[email protected]>
Signed-off-by: Vishnu Reddy <[email protected]>
---
 drivers/media/platform/qcom/venus/core.c | 66 ++++++++++++++++++++++++++++++--
 drivers/media/platform/qcom/venus/core.h |  5 +++
 2 files changed, 68 insertions(+), 3 deletions(-)

diff --git a/drivers/media/platform/qcom/venus/core.c b/drivers/media/platform/qcom/venus/core.c
index 243e342b0ae7..2a0ab553c451 100644
--- a/drivers/media/platform/qcom/venus/core.c
+++ b/drivers/media/platform/qcom/venus/core.c
@@ -377,6 +377,57 @@ static int venus_add_dynamic_nodes(struct venus_core *core)
 static void venus_remove_dynamic_nodes(struct venus_core *core) {}
 #endif
 
+static void venus_unreserve_iova_region(struct device *dev, struct dma_iova_state *state)
+{
+	unsigned int i;
+
+	for (i = 0; dma_iova_size(&state[i]); i++)
+		dma_iova_free(dev, &state[i]);
+}
+
+static int venus_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:
+	venus_unreserve_iova_region(dev, state);
+	dev->bus_dma_limit = dma_limit;
+
+	return ret;
+}
+
 static int venus_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
@@ -421,10 +472,15 @@ static int venus_probe(struct platform_device *pdev)
 			return ret;
 	}
 
-	ret = dma_set_mask_and_coherent(dev, core->res->dma_mask);
+	ret = venus_reserve_iova_region(dev, &core->iova_state, VENUS_NP_RESERVE_IOVA_START,
+					VENUS_NP_RESERVE_IOVA_SIZE);
 	if (ret)
 		goto err_core_put;
 
+	ret = dma_set_mask_and_coherent(dev, core->res->dma_mask);
+	if (ret)
+		goto err_unresv_iova_region;
+
 	dma_set_max_seg_size(dev, UINT_MAX);
 
 	INIT_LIST_HEAD(&core->instances);
@@ -434,13 +490,13 @@ static int venus_probe(struct platform_device *pdev)
 
 	ret = hfi_create(core, &venus_core_ops);
 	if (ret)
-		goto err_core_put;
+		goto err_unresv_iova_region;
 
 	ret = devm_request_threaded_irq(dev, core->irq, hfi_isr, venus_isr_thread,
 					IRQF_TRIGGER_HIGH | IRQF_ONESHOT,
 					"venus", core);
 	if (ret)
-		goto err_core_put;
+		goto err_unresv_iova_region;
 
 	venus_assign_register_offsets(core);
 
@@ -525,6 +581,8 @@ static int venus_probe(struct platform_device *pdev)
 	v4l2_device_unregister(&core->v4l2_dev);
 err_hfi_destroy:
 	hfi_destroy(core);
+err_unresv_iova_region:
+	venus_unreserve_iova_region(dev, core->iova_state);
 err_core_put:
 	if (core->pm_ops->core_put)
 		core->pm_ops->core_put(core);
@@ -562,6 +620,8 @@ static void venus_remove(struct platform_device *pdev)
 
 	hfi_destroy(core);
 
+	venus_unreserve_iova_region(dev, core->iova_state);
+
 	mutex_destroy(&core->pm_lock);
 	mutex_destroy(&core->lock);
 	venus_dbgfs_deinit(core);
diff --git a/drivers/media/platform/qcom/venus/core.h b/drivers/media/platform/qcom/venus/core.h
index 46705a666776..30b8cababe86 100644
--- a/drivers/media/platform/qcom/venus/core.h
+++ b/drivers/media/platform/qcom/venus/core.h
@@ -8,6 +8,7 @@
 #define __VENUS_CORE_H_
 
 #include <linux/bitops.h>
+#include <linux/dma-mapping.h>
 #include <linux/list.h>
 #include <media/videobuf2-v4l2.h>
 #include <media/v4l2-ctrls.h>
@@ -30,6 +31,9 @@
 
 #define VENUS_MAX_FPS			240
 
+#define VENUS_NP_RESERVE_IOVA_START	0x0
+#define VENUS_NP_RESERVE_IOVA_SIZE	0x25800000
+
 extern int venus_fw_debug;
 
 struct freq_tbl {
@@ -250,6 +254,7 @@ struct venus_core {
 	unsigned long dump_core;
 	struct of_changeset *ocs;
 	bool hwmode_dev;
+	struct dma_iova_state *iova_state;
 };
 
 struct vdec_controls {

-- 
2.34.1