[PATCH 1/2] media: iris: 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 allocator, so nothing restricts a
non-pixel buffer to avoid 0 to 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

A series to reserve the 0-600MB IOVA range via "iommu-addresses" was
already posted here:
https://lore.kernel.org/all/[email protected]

Those changes involve DT binding and DT node changes, and discussion is
still ongoing on how to handle those for stable and for the upcoming
sub-node design, with no conclusion reached yet. Thereby a critical reset
issue is still open.

This is an alternate solution to fix the unhandled SMMU page fault
by restricting the IOVA range in the video driver, which also makes it
easier and faster to land on mainline and stable kernels. At the same
time the patch only reserves in the IOVA space without allocating
any physical memory.

Currently sub-nodes are not yet present, and only a single device is
available, so the restriction is applied to both non-pixel and pixel
stream IDs. This makes the solution unoptimal while fixing the issue
considering all scenarios.
Once sub-nodes for non-pixel, pixel, and secure streams become available,
the restriction can be made stream specific.

Fixes: d7378f84e94e ("media: iris: introduce iris core state management with shared queues")
Cc: [email protected]
Signed-off-by: Vishnu Reddy <[email protected]>
---
 drivers/media/platform/qcom/iris/iris_core.h  |  6 +++
 drivers/media/platform/qcom/iris/iris_probe.c | 69 ++++++++++++++++++++++++++-
 2 files changed, 74 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..79bc342a25a2 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: an array of dma_iova_state entries reserved for the 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..f44305ee81b6 100644
--- a/drivers/media/platform/qcom/iris/iris_probe.c
+++ b/drivers/media/platform/qcom/iris/iris_probe.c
@@ -150,6 +150,64 @@ static int iris_init_resources(struct iris_core *core)
 	return iris_init_resets(core);
 }
 
+static int iris_reserve_iova_region(struct device *dev, struct dma_iova_state **iova_state,
+				    unsigned long start, unsigned long size)
+{
+	unsigned long mask = dma_get_mask(dev);
+	unsigned long end, rem, chunk;
+	struct dma_iova_state *state;
+	unsigned int count = 0;
+	int ret;
+
+	state = kcalloc(BITS_PER_TYPE(dma_addr_t) + 1, sizeof(*state), GFP_KERNEL);
+	if (!state)
+		return -ENOMEM;
+
+	end = start + size;
+	rem = end - max(start, PAGE_SIZE);
+
+	ret = dma_set_mask_and_coherent(dev, end - 1);
+	if (ret)
+		goto err_free_mem;
+
+	while (rem) {
+		chunk = min(end & -end, (u64)1 << (fls64(rem) - 1));
+
+		if (!dma_iova_try_alloc(dev, &state[count], 0, chunk)) {
+			ret = -ENOMEM;
+			goto err_free_iova;
+		}
+
+		rem -= chunk;
+		end -= chunk;
+		count++;
+	}
+
+	*iova_state = state;
+	dma_set_mask_and_coherent(dev, mask);
+
+	return 0;
+
+err_free_iova:
+	while (count--)
+		dma_iova_free(dev, &state[count]);
+	dma_set_mask_and_coherent(dev, mask);
+err_free_mem:
+	kfree(state);
+
+	return ret;
+}
+
+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]);
+
+	kfree(iova_state);
+}
+
 static int iris_register_video_device(struct iris_core *core, enum domain_type type)
 {
 	struct video_device *vdev;
@@ -207,6 +265,8 @@ 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);
 }
 
@@ -292,14 +352,21 @@ static int iris_probe(struct platform_device *pdev)
 	dma_set_max_seg_size(&pdev->dev, DMA_BIT_MASK(32));
 	dma_set_seg_boundary(&pdev->dev, DMA_BIT_MASK(32));
 
+	ret = iris_reserve_iova_region(dev, &core->iova_state, IRIS_NP_RESERVE_IOVA_START,
+				       IRIS_NP_RESERVE_IOVA_SIZE);
+	if (ret)
+		goto err_vdev_unreg_enc;
+
 	pm_runtime_set_autosuspend_delay(core->dev, AUTOSUSPEND_DELAY_VALUE);
 	pm_runtime_use_autosuspend(core->dev);
 	ret = devm_pm_runtime_enable(core->dev);
 	if (ret)
-		goto err_vdev_unreg_enc;
+		goto err_unresv_iova_region;
 
 	return 0;
 
+err_unresv_iova_region:
+	iris_unreserve_iova_region(dev, core->iova_state);
 err_vdev_unreg_enc:
 	video_unregister_device(core->vdev_enc);
 err_vdev_unreg_dec:

-- 
2.34.1