[PATCH v2] spi/atmel: add support for runtime PM

[Wenyou Yang]

Drivers should put the device into low power states proactively whenever the
device is not in use. Thus implement support for runtime PM and use the
autosuspend feature to make sure that we can still perform well in case we see
lots of SPI traffic within short period of time.

Signed-off-by: Wenyou Yang <wenyou.yang at atmel.com>
---
Change log
v2:
    add check the return value of clk_prepare_enable().

 drivers/spi/spi-atmel.c |   68 ++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 61 insertions(+), 7 deletions(-)

diff --git a/drivers/spi/spi-atmel.c b/drivers/spi/spi-atmel.c
index 649dcb5..bc9d969 100644
--- a/drivers/spi/spi-atmel.c
+++ b/drivers/spi/spi-atmel.c
@@ -26,6 +26,7 @@
 #include <linux/io.h>
 #include <linux/gpio.h>
 #include <linux/pinctrl/consumer.h>
+#include <linux/pm_runtime.h>
 
 /* SPI register offsets */
 #define SPI_CR					0x0000
@@ -191,6 +192,8 @@
 
 #define SPI_DMA_TIMEOUT		(msecs_to_jiffies(1000))
 
+#define AUTOSUSPEND_TIMEOUT	2000
+
 struct atmel_spi_dma {
 	struct dma_chan			*chan_rx;
 	struct dma_chan			*chan_tx;
@@ -1313,6 +1316,7 @@ static int atmel_spi_probe(struct platform_device *pdev)
 	master->setup = atmel_spi_setup;
 	master->transfer_one_message = atmel_spi_transfer_one_message;
 	master->cleanup = atmel_spi_cleanup;
+	master->auto_runtime_pm = true;
 	platform_set_drvdata(pdev, master);
 
 	as = spi_master_get_devdata(master);
@@ -1385,6 +1389,11 @@ static int atmel_spi_probe(struct platform_device *pdev)
 	dev_info(&pdev->dev, "Atmel SPI Controller at 0x%08lx (irq %d)\n",
 			(unsigned long)regs->start, irq);
 
+	pm_runtime_set_autosuspend_delay(&pdev->dev, AUTOSUSPEND_TIMEOUT);
+	pm_runtime_use_autosuspend(&pdev->dev);
+	pm_runtime_set_active(&pdev->dev);
+	pm_runtime_enable(&pdev->dev);
+
 	ret = devm_spi_register_master(&pdev->dev, master);
 	if (ret)
 		goto out_free_dma;
@@ -1392,6 +1401,9 @@ static int atmel_spi_probe(struct platform_device *pdev)
 	return 0;
 
 out_free_dma:
+	pm_runtime_disable(&pdev->dev);
+	pm_runtime_set_suspended(&pdev->dev);
+
 	if (as->use_dma)
 		atmel_spi_release_dma(as);
 
@@ -1413,6 +1425,8 @@ static int atmel_spi_remove(struct platform_device *pdev)
 	struct spi_master	*master = platform_get_drvdata(pdev);
 	struct atmel_spi	*as = spi_master_get_devdata(master);
 
+	pm_runtime_get_sync(&pdev->dev);
+
 	/* reset the hardware and block queue progress */
 	spin_lock_irq(&as->lock);
 	if (as->use_dma) {
@@ -1430,9 +1444,13 @@ static int atmel_spi_remove(struct platform_device *pdev)
 
 	clk_disable_unprepare(as->clk);
 
+	pm_runtime_put_noidle(&pdev->dev);
+	pm_runtime_disable(&pdev->dev);
+
 	return 0;
 }
 
+#ifdef CONFIG_PM
 #ifdef CONFIG_PM_SLEEP
 static int atmel_spi_suspend(struct device *dev)
 {
@@ -1447,9 +1465,10 @@ static int atmel_spi_suspend(struct device *dev)
 		return ret;
 	}
 
-	clk_disable_unprepare(as->clk);
-
-	pinctrl_pm_select_sleep_state(dev);
+	if (!pm_runtime_suspended(dev)) {
+		clk_disable_unprepare(as->clk);
+		pinctrl_pm_select_sleep_state(dev);
+	}
 
 	return 0;
 }
@@ -1460,9 +1479,12 @@ static int atmel_spi_resume(struct device *dev)
 	struct atmel_spi	*as = spi_master_get_devdata(master);
 	int ret;
 
-	pinctrl_pm_select_default_state(dev);
-
-	clk_prepare_enable(as->clk);
+	if (!pm_runtime_suspended(dev)) {
+		pinctrl_pm_select_default_state(dev);
+		ret = clk_prepare_enable(as->clk);
+		if (ret)
+			return ret;
+	}
 
 	/* Start the queue running */
 	ret = spi_master_resume(master);
@@ -1471,9 +1493,41 @@ static int atmel_spi_resume(struct device *dev)
 
 	return ret;
 }
+#endif
 
-static SIMPLE_DEV_PM_OPS(atmel_spi_pm_ops, atmel_spi_suspend, atmel_spi_resume);
+#ifdef CONFIG_PM_RUNTIME
+static int atmel_spi_runtime_suspend(struct device *dev)
+{
+	struct spi_master *master = dev_get_drvdata(dev);
+	struct atmel_spi *as = spi_master_get_devdata(master);
 
+	clk_disable_unprepare(as->clk);
+	pinctrl_pm_select_sleep_state(dev);
+
+	return 0;
+}
+
+static int atmel_spi_runtime_resume(struct device *dev)
+{
+	struct spi_master *master = dev_get_drvdata(dev);
+	struct atmel_spi *as = spi_master_get_devdata(master);
+	int ret;
+
+	pinctrl_pm_select_default_state(dev);
+
+	ret = clk_prepare_enable(as->clk);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+#endif
+
+static const struct dev_pm_ops atmel_spi_pm_ops = {
+	SET_SYSTEM_SLEEP_PM_OPS(atmel_spi_suspend, atmel_spi_resume)
+	SET_RUNTIME_PM_OPS(atmel_spi_runtime_suspend,
+			   atmel_spi_runtime_resume, NULL)
+};
 #define ATMEL_SPI_PM_OPS	(&atmel_spi_pm_ops)
 #else
 #define ATMEL_SPI_PM_OPS	NULL
-- 
1.7.9.5