spi: spi-mtk-nor: Add power management support

This patch adds dev_pm_ops to mtk-nor to support suspend/resume,
auto suspend delay is set to -1 by default.

Accessing registers are only permitted after its clock is enabled
to deal with unknown state of operating clk at probe time.

Signed-off-by: Ikjoon Jang <ikjn@chromium.org>
Link: https://lore.kernel.org/r/20201006155010.v5.4.I68983b582d949a91866163bab588ff3c2a0d0275@changeid
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-mtk-nor.c

@@ -14,6 +14,7 @@
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/of_device.h>
+#include <linux/pm_runtime.h>
 #include <linux/spi/spi.h>
 #include <linux/spi/spi-mem.h>
 #include <linux/string.h>
@@ -690,22 +691,15 @@ static int mtk_nor_enable_clk(struct mtk_nor *sp)
 	return 0;
 }
 
-static int mtk_nor_init(struct mtk_nor *sp)
+static void mtk_nor_init(struct mtk_nor *sp)
 {
-	int ret;
-
-	ret = mtk_nor_enable_clk(sp);
-	if (ret)
-		return ret;
-
-	sp->spi_freq = clk_get_rate(sp->spi_clk);
+	writel(0, sp->base + MTK_NOR_REG_IRQ_EN);
+	writel(MTK_NOR_IRQ_MASK, sp->base + MTK_NOR_REG_IRQ_STAT);
 
 	writel(MTK_NOR_ENABLE_SF_CMD, sp->base + MTK_NOR_REG_WP);
 	mtk_nor_rmw(sp, MTK_NOR_REG_CFG2, MTK_NOR_WR_CUSTOM_OP_EN, 0);
 	mtk_nor_rmw(sp, MTK_NOR_REG_CFG3,
 		    MTK_NOR_DISABLE_WREN | MTK_NOR_DISABLE_SR_POLL, 0);
-
-	return ret;
 }
 
 static irqreturn_t mtk_nor_irq_handler(int irq, void *data)
@@ -788,6 +782,7 @@ static int mtk_nor_probe(struct platform_device *pdev)
 	ctlr->num_chipselect = 1;
 	ctlr->setup = mtk_nor_setup;
 	ctlr->transfer_one_message = mtk_nor_transfer_one_message;
+	ctlr->auto_runtime_pm = true;
 
 	dev_set_drvdata(&pdev->dev, ctlr);
 
@@ -811,12 +806,19 @@ static int mtk_nor_probe(struct platform_device *pdev)
 		return -ENOMEM;
 	}
 
+	ret = mtk_nor_enable_clk(sp);
+	if (ret < 0)
+		return ret;
+
+	sp->spi_freq = clk_get_rate(sp->spi_clk);
+
+	mtk_nor_init(sp);
+
 	irq = platform_get_irq_optional(pdev, 0);
+
 	if (irq < 0) {
 		dev_warn(sp->dev, "IRQ not available.");
 	} else {
-		writel(MTK_NOR_IRQ_MASK, base + MTK_NOR_REG_IRQ_STAT);
-		writel(0, base + MTK_NOR_REG_IRQ_EN);
 		ret = devm_request_irq(sp->dev, irq, mtk_nor_irq_handler, 0,
 				       pdev->name, sp);
 		if (ret < 0) {
@@ -827,34 +829,86 @@ static int mtk_nor_probe(struct platform_device *pdev)
 		}
 	}
 
-	ret = mtk_nor_init(sp);
-	if (ret < 0) {
-		kfree(ctlr);
-		return ret;
-	}
+	pm_runtime_set_autosuspend_delay(&pdev->dev, -1);
+	pm_runtime_use_autosuspend(&pdev->dev);
+	pm_runtime_set_active(&pdev->dev);
+	pm_runtime_enable(&pdev->dev);
+	pm_runtime_get_noresume(&pdev->dev);
+
+	ret = devm_spi_register_controller(&pdev->dev, ctlr);
+	if (ret < 0)
+		goto err_probe;
+
+	pm_runtime_mark_last_busy(&pdev->dev);
+	pm_runtime_put_autosuspend(&pdev->dev);
 
 	dev_info(&pdev->dev, "spi frequency: %d Hz\n", sp->spi_freq);
 
-	return devm_spi_register_controller(&pdev->dev, ctlr);
+	return 0;
+
+err_probe:
+	pm_runtime_disable(&pdev->dev);
+	pm_runtime_set_suspended(&pdev->dev);
+	pm_runtime_dont_use_autosuspend(&pdev->dev);
+
+	mtk_nor_disable_clk(sp);
+
+	return ret;
 }
 
 static int mtk_nor_remove(struct platform_device *pdev)
 {
-	struct spi_controller *ctlr;
-	struct mtk_nor *sp;
+	struct spi_controller *ctlr = dev_get_drvdata(&pdev->dev);
+	struct mtk_nor *sp = spi_controller_get_devdata(ctlr);
 
-	ctlr = dev_get_drvdata(&pdev->dev);
-	sp = spi_controller_get_devdata(ctlr);
+	pm_runtime_disable(&pdev->dev);
+	pm_runtime_set_suspended(&pdev->dev);
+	pm_runtime_dont_use_autosuspend(&pdev->dev);
 
 	mtk_nor_disable_clk(sp);
 
 	return 0;
 }
 
+static int __maybe_unused mtk_nor_runtime_suspend(struct device *dev)
+{
+	struct spi_controller *ctlr = dev_get_drvdata(dev);
+	struct mtk_nor *sp = spi_controller_get_devdata(ctlr);
+
+	mtk_nor_disable_clk(sp);
+
+	return 0;
+}
+
+static int __maybe_unused mtk_nor_runtime_resume(struct device *dev)
+{
+	struct spi_controller *ctlr = dev_get_drvdata(dev);
+	struct mtk_nor *sp = spi_controller_get_devdata(ctlr);
+
+	return mtk_nor_enable_clk(sp);
+}
+
+static int __maybe_unused mtk_nor_suspend(struct device *dev)
+{
+	return pm_runtime_force_suspend(dev);
+}
+
+static int __maybe_unused mtk_nor_resume(struct device *dev)
+{
+	return pm_runtime_force_resume(dev);
+}
+
+static const struct dev_pm_ops mtk_nor_pm_ops = {
+	SET_RUNTIME_PM_OPS(mtk_nor_runtime_suspend,
+			   mtk_nor_runtime_resume, NULL)
+	SET_SYSTEM_SLEEP_PM_OPS(mtk_nor_suspend, mtk_nor_resume)
+};
+
 static struct platform_driver mtk_nor_driver = {
 	.driver = {
 		.name = DRIVER_NAME,
 		.of_match_table = mtk_nor_match,
+		.pm = &mtk_nor_pm_ops,
 	},
 	.probe = mtk_nor_probe,
 	.remove = mtk_nor_remove,