[PATCH v2 2/3] hwrng: mtk - add runtime PM support

[sean.wang]

From: Sean Wang <sean.w...@mediatek.com>

Add runtime PM support.  There will be the benefit on SoCs where the
clock to the RNG used can be shutdown.

Signed-off-by: Sean Wang <sean.w...@mediatek.com>
---
 drivers/char/hw_random/mtk-rng.c | 42 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/drivers/char/hw_random/mtk-rng.c b/drivers/char/hw_random/mtk-rng.c
index df8eb54..8da7bcf 100644
--- a/drivers/char/hw_random/mtk-rng.c
+++ b/drivers/char/hw_random/mtk-rng.c
@@ -25,6 +25,10 @@
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/platform_device.h>
+#include <linux/pm_runtime.h>
+
+/* Runtime PM autosuspend timeout: */
+#define RNG_AUTOSUSPEND_TIMEOUT                100
 
 #define USEC_POLL                      2
 #define TIMEOUT_POLL                   20
@@ -90,6 +94,8 @@ static int mtk_rng_read(struct hwrng *rng, void *buf, size_t 
max, bool wait)
        struct mtk_rng *priv = to_mtk_rng(rng);
        int retval = 0;
 
+       pm_runtime_get_sync((struct device *)priv->rng.priv);
+
        while (max >= sizeof(u32)) {
                if (!mtk_rng_wait_ready(rng, wait))
                        break;
@@ -100,6 +106,9 @@ static int mtk_rng_read(struct hwrng *rng, void *buf, 
size_t max, bool wait)
                max -= sizeof(u32);
        }
 
+       pm_runtime_mark_last_busy((struct device *)priv->rng.priv);
+       pm_runtime_put_sync_autosuspend((struct device *)priv->rng.priv);
+
        return retval || !wait ? retval : -EIO;
 }
 
@@ -120,9 +129,12 @@ static int mtk_rng_probe(struct platform_device *pdev)
                return -ENOMEM;
 
        priv->rng.name = pdev->name;
+#ifndef CONFIG_PM
        priv->rng.init = mtk_rng_init;
        priv->rng.cleanup = mtk_rng_cleanup;
+#endif
        priv->rng.read = mtk_rng_read;
+       priv->rng.priv = (unsigned long)&pdev->dev;
 
        priv->clk = devm_clk_get(&pdev->dev, "rng");
        if (IS_ERR(priv->clk)) {
@@ -142,11 +154,40 @@ static int mtk_rng_probe(struct platform_device *pdev)
                return ret;
        }
 
+       dev_set_drvdata(&pdev->dev, priv);
+       pm_runtime_set_autosuspend_delay(&pdev->dev, RNG_AUTOSUSPEND_TIMEOUT);
+       pm_runtime_use_autosuspend(&pdev->dev);
+       pm_runtime_enable(&pdev->dev);
+
        dev_info(&pdev->dev, "registered RNG driver\n");
 
        return 0;
 }
 
+#ifdef CONFIG_PM
+static int mtk_rng_runtime_suspend(struct device *dev)
+{
+       struct mtk_rng *priv = dev_get_drvdata(dev);
+
+       mtk_rng_cleanup(&priv->rng);
+
+       return 0;
+}
+
+static int mtk_rng_runtime_resume(struct device *dev)
+{
+       struct mtk_rng *priv = dev_get_drvdata(dev);
+
+       return mtk_rng_init(&priv->rng);
+}
+
+static UNIVERSAL_DEV_PM_OPS(mtk_rng_pm_ops, mtk_rng_runtime_suspend,
+                           mtk_rng_runtime_resume, NULL);
+#define MTK_RNG_PM_OPS (&mtk_rng_pm_ops)
+#else  /* CONFIG_PM */
+#define MTK_RNG_PM_OPS NULL
+#endif /* CONFIG_PM */
+
 static const struct of_device_id mtk_rng_match[] = {
        { .compatible = "mediatek,mt7623-rng" },
        {},
@@ -157,6 +198,7 @@ static int mtk_rng_probe(struct platform_device *pdev)
        .probe          = mtk_rng_probe,
        .driver = {
                .name = MTK_RNG_DEV,
+               .pm = MTK_RNG_PM_OPS,
                .of_match_table = mtk_rng_match,
        },
 };
-- 
1.9.1