iommu/mediatek: Add device link for smi-common and m4u

In the lastest SoC, M4U has its special power domain. thus, If the engine
begin to work, it should help enable the power for M4U firstly.
Currently if the engine work, it always enable the power/clocks for
smi-larbs/smi-common. This patch adds device_link for smi-common and M4U.
then, if smi-common power is enabled, the M4U power also is powered on
automatically.

Normally M4U connect with several smi-larbs and their smi-common always
are the same, In this patch it get smi-common dev from the last smi-larb
device, then add the device_link.

Signed-off-by: Yong Wu <yong.wu@mediatek.com>
Reviewed-by: Tomasz Figa <tfiga@chromium.org>
Link: https://lore.kernel.org/r/20210111111914.22211-19-yong.wu@mediatek.com
Signed-off-by: Will Deacon <will@kernel.org>

drivers/iommu/mtk_iommu.c

@@ -20,6 +20,7 @@
 #include <linux/of_irq.h>
 #include <linux/of_platform.h>
 #include <linux/platform_device.h>
+#include <linux/pm_runtime.h>
 #include <linux/regmap.h>
 #include <linux/slab.h>
 #include <linux/spinlock.h>
@@ -633,6 +634,9 @@ static int mtk_iommu_probe(struct platform_device *pdev)
 {
 	struct mtk_iommu_data   *data;
 	struct device           *dev = &pdev->dev;
+	struct device_node	*larbnode, *smicomm_node;
+	struct platform_device	*plarbdev;
+	struct device_link	*link;
 	struct resource         *res;
 	resource_size_t		ioaddr;
 	struct component_match  *match = NULL;
@@ -699,8 +703,6 @@ static int mtk_iommu_probe(struct platform_device *pdev)
 		return larb_nr;
 
 	for (i = 0; i < larb_nr; i++) {
-		struct device_node *larbnode;
-		struct platform_device *plarbdev;
 		u32 id;
 
 		larbnode = of_parse_phandle(dev->of_node, "mediatek,larbs", i);
@@ -727,12 +729,28 @@ static int mtk_iommu_probe(struct platform_device *pdev)
 					    compare_of, larbnode);
 	}
 
+	/* Get smi-common dev from the last larb. */
+	smicomm_node = of_parse_phandle(larbnode, "mediatek,smi", 0);
+	if (!smicomm_node)
+		return -EINVAL;
+
+	plarbdev = of_find_device_by_node(smicomm_node);
+	of_node_put(smicomm_node);
+	data->smicomm_dev = &plarbdev->dev;
+
+	link = device_link_add(data->smicomm_dev, dev,
+			DL_FLAG_STATELESS | DL_FLAG_PM_RUNTIME);
+	if (!link) {
+		dev_err(dev, "Unable link %s.\n", dev_name(data->smicomm_dev));
+		return -EINVAL;
+	}
+
 	platform_set_drvdata(pdev, data);
 
 	ret = iommu_device_sysfs_add(&data->iommu, dev, NULL,
 				     "mtk-iommu.%pa", &ioaddr);
 	if (ret)
-		return ret;
+		goto out_link_remove;
 
 	iommu_device_set_ops(&data->iommu, &mtk_iommu_ops);
 	iommu_device_set_fwnode(&data->iommu, &pdev->dev.of_node->fwnode);
@@ -762,6 +780,8 @@ static int mtk_iommu_probe(struct platform_device *pdev)
 	iommu_device_unregister(&data->iommu);
 out_sysfs_remove:
 	iommu_device_sysfs_remove(&data->iommu);
+out_link_remove:
+	device_link_remove(data->smicomm_dev, dev);
 	return ret;
 }
 
@@ -776,6 +796,7 @@ static int mtk_iommu_remove(struct platform_device *pdev)
 		bus_set_iommu(&platform_bus_type, NULL);
 
 	clk_disable_unprepare(data->bclk);
+	device_link_remove(data->smicomm_dev, &pdev->dev);
 	devm_free_irq(&pdev->dev, data->irq, data);
 	component_master_del(&pdev->dev, &mtk_iommu_com_ops);
 	return 0;

drivers/iommu/mtk_iommu.h

@@ -68,6 +68,7 @@ struct mtk_iommu_data {
 
 	struct iommu_device		iommu;
 	const struct mtk_iommu_plat_data *plat_data;
+	struct device			*smicomm_dev;
 
 	struct dma_iommu_mapping	*mapping; /* For mtk_iommu_v1.c */