[PATCH] spi: sprd: add runtime pm for transfer message

[Chunyan Zhang]

From: Bangzheng Liu <bangzheng.liu@xxxxxxxxxx>

Before transfer one message, spi core would set chipselect, sprd spi
device should be resumed from runtime suspend, otherwise kernel would
crash once access spi registers. The sprd spi device can be suspended
until clearing chipselect which would be executed after transfer.

Fixes: e7d973a31c24 ("spi: sprd: Add SPI driver for Spreadtrum SC9860")
Signed-off-by: Bangzheng Liu <bangzheng.liu@xxxxxxxxxx>
Signed-off-by: Chunyan Zhang <chunyan.zhang@xxxxxxxxxx>
---
 drivers/spi/spi-sprd.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/drivers/spi/spi-sprd.c b/drivers/spi/spi-sprd.c
index 635738f54c73..1733d10eb296 100644
--- a/drivers/spi/spi-sprd.c
+++ b/drivers/spi/spi-sprd.c
@@ -293,15 +293,25 @@ static void sprd_spi_chipselect(struct spi_device *sdev, bool cs)
 	struct spi_controller *sctlr = sdev->controller;
 	struct sprd_spi *ss = spi_controller_get_devdata(sctlr);
 	u32 val;
+	int ret;
 
-	val = readl_relaxed(ss->base + SPRD_SPI_CTL0);
 	/*  The SPI controller will pull down CS pin if cs is 0 */
 	if (!cs) {
-		val &= ~SPRD_SPI_CS0_VALID;
+		ret = pm_runtime_get_sync(ss->dev);
+		if (ret < 0) {
+			pm_runtime_put_noidle(ss->dev);
+			dev_err(ss->dev, "Failed to power device: %d\n", ret);
+			return;
+		}
+		val = readl_relaxed(ss->base + SPRD_SPI_CTL0);
+		val &= ~SPRD_SPI_CS0_VALID; /* set cs0 valid */
 		writel_relaxed(val, ss->base + SPRD_SPI_CTL0);
 	} else {
-		val |= SPRD_SPI_CSN_MASK;
+		val = readl_relaxed(ss->base + SPRD_SPI_CTL0);
+		val |= SPRD_SPI_CSN_MASK; /* set all cs invalid */
 		writel_relaxed(val, ss->base + SPRD_SPI_CTL0);
+		pm_runtime_mark_last_busy(ss->dev);
+		pm_runtime_put_autosuspend(ss->dev);
 	}
 }
 
-- 
2.20.1