On 03/08/15 11:21, Yong Wu wrote:
This patch adds support for mediatek m4u (MultiMedia Memory Management
Unit).
Signed-off-by: Yong Wu <yong.wu@xxxxxxxxxxxx>
---
[...]
+/*
+ * There is only one iommu domain called the m4u domain that
+ * all Multimedia modules share.
+ */
+static struct mtk_iommu_domain *m4udom;
It's a shame this can't be part of the m4u device's mtk_iommu_data, but
since the way iommu_domain_alloc works makes that impossible, I think we
have little choice but to use the global and hope your guys never build
a system with two of these things in ;)
[...]
+static struct iommu_domain *mtk_iommu_domain_alloc(unsigned type)
+{
+ struct mtk_iommu_domain *priv;
+
+ if (type != IOMMU_DOMAIN_UNMANAGED && type != IOMMU_DOMAIN_DMA)
+ return NULL;
+
+ if (m4udom)/* The m4u domain exist. */
+ return &m4udom->domain;
+
+ priv = kzalloc(sizeof(*priv), GFP_KERNEL);
+ if (!priv)
+ return NULL;
+
+ priv->domain.geometry.aperture_start = 0;
+ priv->domain.geometry.aperture_end = DMA_BIT_MASK(32);
+ priv->domain.geometry.force_aperture = true;
My intention is that in the IOMMU_DOMAIN_DMA case you'd call
iommu_get_dma_cookie(&priv->domain) here as well, that way I can get rid
of some of the dodgy workarounds in arch_setup_dma_ops which try to
cover all possible cases (and which I'm now not 100% confident in). I'm
just about to start trying to fix that up (expect a repost of my series
in a week or two once -rc1 has landed).
+
+ m4udom = priv;
+
+ return &priv->domain;
+}
[...]
+static int mtk_iommu_add_device(struct device *dev)
+{
+ struct iommu_group *group;
+ int ret;
+
+ if (!dev->archdata.iommu) /* Not a iommu client device */
+ return -ENODEV;
+
+ group = iommu_group_get(dev);
+ if (!group) {
+ group = iommu_group_alloc();
+ if (IS_ERR(group)) {
+ dev_err(dev, "Failed to allocate IOMMU group\n");
+ return PTR_ERR(group);
+ }
+ }
+
> + ret = iommu_group_add_device(group, dev);
+ if (ret) {
+ dev_err(dev, "Failed to add IOMMU group\n");
+ goto err_group_put;
+ }
I know the rest of the code means that you can't hit it in practice, but
if you ever did have two client devices in the same group then the
iommu_group_get() could legitimately succeed for the second device, then
you'd blow up creating a duplicate sysfs entry by adding the device to
its own group again. Probably not what you want.
+
+ ret = iommu_attach_group(&m4udom->domain, group);
+ if (ret)
+ dev_err(dev, "Failed to attach IOMMU group\n");
Similarly here, if two devices did share a group then the group could
legitimately already be attached to a domain here (by the first device),
so attaching it again would be wrong. I think it would be nicer to check
with iommu_get_domain_for_dev() first to see if you need to do anything
at all (a valid domain from that implies a valid group).
+
+err_group_put:
+ iommu_group_put(group);
+ return ret;
+}
[...]
+static int mtk_iommu_probe(struct platform_device *pdev)
+{
+ struct mtk_iommu_data *data;
+ struct device *dev = &pdev->dev;
+ void __iomem *protect;
+ int ret;
+
+ data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
+ if (!data)
+ return -ENOMEM;
+
+ /* Protect memory. HW will access here while translation fault.*/
+ protect = devm_kzalloc(dev, MTK_PROTECT_PA_ALIGN * 2, GFP_KERNEL);
+ if (!protect)
+ return -ENOMEM;
+ data->protect_base = virt_to_phys(protect);
+
+ ret = mtk_iommu_parse_dt(pdev, data);
+ if (ret)
+ return ret;
+
+ if (!m4udom)/* There is no iommu client */
+ return 0;
I don't quite follow this: m4udom is apparently only created by someone
calling domain_alloc() - how can you guarantee that happens before this
driver is probed? - but if they then go and try to attach the device to
their new domain, it's going to end up in mtk_hw_init() poking the
hardware of the m4u device that can't have even probed yet.
I can only imagine it currently works by sheer chance due to the
horrible arch_setup_dma_ops delayed attachment workaround, so even if I
can't remove that completely when I look at it next week I'm liable to
change it in a way that breaks this badly ;)
Robin.
+
+ data->dev = dev;
+ m4udom->data = data;
+ dev_set_drvdata(dev, m4udom);
+
+ return 0;
+}
--
To unsubscribe from this list: send the line "unsubscribe devicetree" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
