[PATCH v8] mmc: sdhci-of-dwcmshc: Add runtime PM operations

[Liming Sun <limings@nvidia.com>]

This commit implements the runtime PM operations to disable eMMC
card clock when idle.

Reviewed-by: David Thompson <davthompson@nvidia.com>
Signed-off-by: Liming Sun <limings@nvidia.com>
---
v7->v8:
    - Address Ulf's comment (option-1);
    - Updates for Adrian;s comment to remove the force_suspend/resume
      in dwcmshc_resume()/dwcmshc_suspend(); Add comments for
      dwcmshc_resume()/dwcmshc_suspend();
v6->v7:
    - Address Ulf's comment;
v5->v6:
    - Address Adrian's more comments and add coordination between
      runtime PM and system PM;
v4->v5:
    - Address Adrian's comment to move the pm_enable to the end to
      avoid race;
v3->v4:
    - Fix compiling reported by 'kernel test robot';
v2->v3:
    - Revise the commit message;
v1->v2:
    Updates for comments from Ulf:
    - Make the runtime PM logic generic for sdhci-of-dwcmshc;
v1: Initial version.
---
 drivers/mmc/host/sdhci-of-dwcmshc.c | 76 +++++++++++++++++++++++++++--
 1 file changed, 73 insertions(+), 3 deletions(-)

diff --git a/drivers/mmc/host/sdhci-of-dwcmshc.c b/drivers/mmc/host/sdhci-of-dwcmshc.c
index e68cd87998c8..2196218c9d79 100644
--- a/drivers/mmc/host/sdhci-of-dwcmshc.c
+++ b/drivers/mmc/host/sdhci-of-dwcmshc.c
@@ -15,6 +15,7 @@
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/of_device.h>
+#include <linux/pm_runtime.h>
 #include <linux/reset.h>
 #include <linux/sizes.h>
 
@@ -548,9 +549,13 @@ static int dwcmshc_probe(struct platform_device *pdev)
 
 	host->mmc->caps |= MMC_CAP_WAIT_WHILE_BUSY;
 
+	pm_runtime_get_noresume(dev);
+	pm_runtime_set_active(dev);
+	pm_runtime_enable(dev);
+
 	err = sdhci_setup_host(host);
 	if (err)
-		goto err_clk;
+		goto err_rpm;
 
 	if (rk_priv)
 		dwcmshc_rk35xx_postinit(host, priv);
@@ -559,10 +564,15 @@ static int dwcmshc_probe(struct platform_device *pdev)
 	if (err)
 		goto err_setup_host;
 
+	pm_runtime_put(dev);
+
 	return 0;
 
 err_setup_host:
 	sdhci_cleanup_host(host);
+err_rpm:
+	pm_runtime_disable(dev);
+	pm_runtime_put_noidle(dev);
 err_clk:
 	clk_disable_unprepare(pltfm_host->clk);
 	clk_disable_unprepare(priv->bus_clk);
@@ -594,6 +604,10 @@ static int dwcmshc_remove(struct platform_device *pdev)
 }
 
 #ifdef CONFIG_PM_SLEEP
+/*
+ * Note, runtime suspend changes only SDHCI_CLOCK_CARD_EN which has no effect on
+ * system suspend.
+ */
 static int dwcmshc_suspend(struct device *dev)
 {
 	struct sdhci_host *host = dev_get_drvdata(dev);
@@ -602,9 +616,11 @@ static int dwcmshc_suspend(struct device *dev)
 	struct rk35xx_priv *rk_priv = priv->priv;
 	int ret;
 
+	pm_runtime_get_sync(dev);
+
 	ret = sdhci_suspend_host(host);
 	if (ret)
-		return ret;
+		goto err_suspend;
 
 	clk_disable_unprepare(pltfm_host->clk);
 	if (!IS_ERR(priv->bus_clk))
@@ -614,9 +630,15 @@ static int dwcmshc_suspend(struct device *dev)
 		clk_bulk_disable_unprepare(RK35xx_MAX_CLKS,
 					   rk_priv->rockchip_clks);
 
+err_suspend:
+	pm_runtime_put_noidle(dev);
 	return ret;
 }
 
+/*
+ * Note, system resume leaves SDHCI_CLOCK_INT_EN off which is consistent with
+ * either runtime suspended or runtime resumed.
+ */
 static int dwcmshc_resume(struct device *dev)
 {
 	struct sdhci_host *host = dev_get_drvdata(dev);
@@ -646,7 +668,55 @@ static int dwcmshc_resume(struct device *dev)
 }
 #endif
 
-static SIMPLE_DEV_PM_OPS(dwcmshc_pmops, dwcmshc_suspend, dwcmshc_resume);
+#ifdef CONFIG_PM
+
+static void dwcmshc_enable_card_clk(struct sdhci_host *host)
+{
+	u16 ctrl;
+
+	ctrl = sdhci_readw(host, SDHCI_CLOCK_CONTROL);
+	if ((ctrl & SDHCI_CLOCK_INT_EN) && !(ctrl & SDHCI_CLOCK_CARD_EN)) {
+		ctrl |= SDHCI_CLOCK_CARD_EN;
+		sdhci_writew(host, ctrl, SDHCI_CLOCK_CONTROL);
+	}
+}
+
+static void dwcmshc_disable_card_clk(struct sdhci_host *host)
+{
+	u16 ctrl;
+
+	ctrl = sdhci_readw(host, SDHCI_CLOCK_CONTROL);
+	if (ctrl & SDHCI_CLOCK_CARD_EN) {
+		ctrl &= ~SDHCI_CLOCK_CARD_EN;
+		sdhci_writew(host, ctrl, SDHCI_CLOCK_CONTROL);
+	}
+}
+
+static int dwcmshc_runtime_suspend(struct device *dev)
+{
+	struct sdhci_host *host = dev_get_drvdata(dev);
+
+	dwcmshc_disable_card_clk(host);
+
+	return 0;
+}
+
+static int dwcmshc_runtime_resume(struct device *dev)
+{
+	struct sdhci_host *host = dev_get_drvdata(dev);
+
+	dwcmshc_enable_card_clk(host);
+
+	return 0;
+}
+
+#endif
+
+static const struct dev_pm_ops dwcmshc_pmops = {
+	SET_SYSTEM_SLEEP_PM_OPS(dwcmshc_suspend, dwcmshc_resume)
+	SET_RUNTIME_PM_OPS(dwcmshc_runtime_suspend,
+			   dwcmshc_runtime_resume, NULL)
+};
 
 static struct platform_driver sdhci_dwcmshc_driver = {
 	.driver	= {
-- 
2.30.1