[PATCH v2 3/7] iommu/rockchip: support virtual iommu slave device

[Shunqian Zheng]

An virtual master device like DRM need to attach to iommu
domain to share the domain with VOP(the one with actual
iommu slave). We currently check the group is NULL to indicate
a virtual master, which is not true since we decide to use
the common iommu api to attach device in DRM.

With this patch, we can probe a virtual iommu device and
allow the DRM attaching to it. The virtual iommu is needed also
because we want convert to use DMA API for map/unmap, cache flush,
so that DRM buffer alloc still work even VOP is disabled.

Signed-off-by: Shunqian Zheng <zhengsq@xxxxxxxxxxxxxx>
---
 drivers/iommu/rockchip-iommu.c | 37 +++++++++++++++++++++++++------------
 1 file changed, 25 insertions(+), 12 deletions(-)

diff --git a/drivers/iommu/rockchip-iommu.c b/drivers/iommu/rockchip-iommu.c
index 3c16ec3..d6c3051 100644
--- a/drivers/iommu/rockchip-iommu.c
+++ b/drivers/iommu/rockchip-iommu.c
@@ -75,6 +75,11 @@
 
 #define IOMMU_REG_POLL_COUNT_FAST 1000
 
+/* A virtual iommu in device-tree registered without reg or
+ * interrupts, so the num_mmu is zero.
+ */
+#define RK_IOMMU_IS_VIRTUAL(iommu) (iommu->num_mmu == 0)
+
 struct rk_iommu_domain {
 	struct list_head iommus;
 	u32 *dt; /* page directory table */
@@ -789,13 +794,13 @@ static int rk_iommu_attach_device(struct iommu_domain *domain,
 	int ret, i;
 	phys_addr_t dte_addr;
 
-	/*
-	 * Allow 'virtual devices' (e.g., drm) to attach to domain.
-	 * Such a device does not belong to an iommu group.
-	 */
 	iommu = rk_iommu_from_dev(dev);
-	if (!iommu)
+
+	iommu->domain = domain;
+	if (RK_IOMMU_IS_VIRTUAL(iommu)) {
+		dev_dbg(dev, "Attach virtual device to iommu domain\n");
 		return 0;
+	}
 
 	ret = rk_iommu_enable_stall(iommu);
 	if (ret)
@@ -805,7 +810,6 @@ static int rk_iommu_attach_device(struct iommu_domain *domain,
 	if (ret)
 		return ret;
 
-	iommu->domain = domain;
 
 	ret = devm_request_irq(iommu->dev, iommu->irq, rk_iommu_irq,
 			       IRQF_SHARED, dev_name(dev), iommu);
@@ -842,10 +846,13 @@ static void rk_iommu_detach_device(struct iommu_domain *domain,
 	unsigned long flags;
 	int i;
 
-	/* Allow 'virtual devices' (eg drm) to detach from domain */
 	iommu = rk_iommu_from_dev(dev);
-	if (!iommu)
+
+	iommu->domain = NULL;
+	if (RK_IOMMU_IS_VIRTUAL(iommu)) {
+		dev_dbg(dev, "Master with virtual iommu detached from domain\n");
 		return;
+	}
 
 	spin_lock_irqsave(&rk_domain->iommus_lock, flags);
 	list_del_init(&iommu->node);
@@ -862,8 +869,6 @@ static void rk_iommu_detach_device(struct iommu_domain *domain,
 
 	devm_free_irq(iommu->dev, iommu->irq, iommu);
 
-	iommu->domain = NULL;
-
 	dev_dbg(dev, "Detached from iommu domain\n");
 }
 
@@ -1034,6 +1039,7 @@ static int rk_iommu_probe(struct platform_device *pdev)
 	struct device *dev = &pdev->dev;
 	struct rk_iommu *iommu;
 	struct resource *res;
+	int num_res = pdev->num_resources;
 	int i;
 
 	iommu = devm_kzalloc(dev, sizeof(*iommu), GFP_KERNEL);
@@ -1043,12 +1049,19 @@ static int rk_iommu_probe(struct platform_device *pdev)
 	platform_set_drvdata(pdev, iommu);
 	iommu->dev = dev;
 	iommu->num_mmu = 0;
-	iommu->bases = devm_kzalloc(dev, sizeof(*iommu->bases) * iommu->num_mmu,
+
+	if (!num_res) {
+		iommu->bases = NULL;
+		dev_info(dev, "this is a virtual iommu\n");
+		return 0;
+	}
+
+	iommu->bases = devm_kzalloc(dev, sizeof(*iommu->bases) * num_res,
 				    GFP_KERNEL);
 	if (!iommu->bases)
 		return -ENOMEM;
 
-	for (i = 0; i < pdev->num_resources; i++) {
+	for (i = 0; i < num_res; i++) {
 		res = platform_get_resource(pdev, IORESOURCE_MEM, i);
 		if (!res)
 			continue;
-- 
1.9.1