memory: mtk-smi: Add device-link between smi-larb and smi-common

Normally, If the smi-larb HW need work, we should enable the smi-common
HW power and clock firstly.
This patch adds device-link between the smi-larb dev and the smi-common
dev. then If pm_runtime_get_sync(smi-larb-dev), the pm_runtime_get_sync
(smi-common-dev) will be called automatically.

Also, Add DL_FLAG_STATELESS to avoid the smi-common clocks be gated when
probe.

CC: Matthias Brugger <matthias.bgg@gmail.com>
Suggested-by: Tomasz Figa <tfiga@chromium.org>
Signed-off-by: Yong Wu <yong.wu@mediatek.com>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Link: https://lore.kernel.org/r/20210410091128.31823-5-yong.wu@mediatek.com

drivers/memory/mtk-smi.c

@@ -319,6 +319,7 @@ static int mtk_smi_larb_probe(struct platform_device *pdev)
 	struct device *dev = &pdev->dev;
 	struct device_node *smi_node;
 	struct platform_device *smi_pdev;
+	struct device_link *link;
 
 	larb = devm_kzalloc(dev, sizeof(*larb), GFP_KERNEL);
 	if (!larb)
@@ -358,6 +359,12 @@ static int mtk_smi_larb_probe(struct platform_device *pdev)
 		if (!platform_get_drvdata(smi_pdev))
 			return -EPROBE_DEFER;
 		larb->smi_common_dev = &smi_pdev->dev;
+		link = device_link_add(dev, larb->smi_common_dev,
+				       DL_FLAG_PM_RUNTIME | DL_FLAG_STATELESS);
+		if (!link) {
+			dev_err(dev, "Unable to link smi-common dev\n");
+			return -ENODEV;
+		}
 	} else {
 		dev_err(dev, "Failed to get the smi_common device\n");
 		return -EINVAL;
@@ -370,6 +377,9 @@ static int mtk_smi_larb_probe(struct platform_device *pdev)
 
 static int mtk_smi_larb_remove(struct platform_device *pdev)
 {
+	struct mtk_smi_larb *larb = platform_get_drvdata(pdev);
+
+	device_link_remove(&pdev->dev, larb->smi_common_dev);
 	pm_runtime_disable(&pdev->dev);
 	component_del(&pdev->dev, &mtk_smi_larb_component_ops);
 	return 0;
@@ -381,17 +391,9 @@ static int __maybe_unused mtk_smi_larb_resume(struct device *dev)
 	const struct mtk_smi_larb_gen *larb_gen = larb->larb_gen;
 	int ret;
 
-	/* Power on smi-common. */
-	ret = pm_runtime_resume_and_get(larb->smi_common_dev);
-	if (ret < 0) {
-		dev_err(dev, "Failed to pm get for smi-common(%d).\n", ret);
-		return ret;
-	}
-
 	ret = mtk_smi_clk_enable(&larb->smi);
 	if (ret < 0) {
 		dev_err(dev, "Failed to enable clock(%d).\n", ret);
-		pm_runtime_put_sync(larb->smi_common_dev);
 		return ret;
 	}
 
@@ -406,7 +408,6 @@ static int __maybe_unused mtk_smi_larb_suspend(struct device *dev)
 	struct mtk_smi_larb *larb = dev_get_drvdata(dev);
 
 	mtk_smi_clk_disable(&larb->smi);
-	pm_runtime_put_sync(larb->smi_common_dev);
 	return 0;
 }