[PATCH 3.16 186/328] spi: tegra20-slink: explicitly enable/disable clock

[Ben Hutchings <ben@xxxxxxxxxxxxxxx>]

3.16.62-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Marcel Ziswiler <marcel.ziswiler@xxxxxxxxxxx>

commit 7001cab1dabc0b72b2b672ef58a90ab64f5e2343 upstream.

Depending on the SPI instance one may get an interrupt storm upon
requesting resp. interrupt unless the clock is explicitly enabled
beforehand. This has been observed trying to bring up instance 4 on
T20.

Signed-off-by: Marcel Ziswiler <marcel.ziswiler@xxxxxxxxxxx>
Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/spi/spi-tegra20-slink.c | 31 +++++++++++++++++++++++--------
 1 file changed, 23 insertions(+), 8 deletions(-)

--- a/drivers/spi/spi-tegra20-slink.c
+++ b/drivers/spi/spi-tegra20-slink.c
@@ -1063,6 +1063,24 @@ static int tegra_slink_probe(struct plat
 		goto exit_free_master;
 	}
 
+	/* disabled clock may cause interrupt storm upon request */
+	tspi->clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(tspi->clk)) {
+		ret = PTR_ERR(tspi->clk);
+		dev_err(&pdev->dev, "Can not get clock %d\n", ret);
+		goto exit_free_master;
+	}
+	ret = clk_prepare(tspi->clk);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "Clock prepare failed %d\n", ret);
+		goto exit_free_master;
+	}
+	ret = clk_enable(tspi->clk);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "Clock enable failed %d\n", ret);
+		goto exit_free_master;
+	}
+
 	spi_irq = platform_get_irq(pdev, 0);
 	tspi->irq = spi_irq;
 	ret = request_threaded_irq(tspi->irq, tegra_slink_isr,
@@ -1071,14 +1089,7 @@ static int tegra_slink_probe(struct plat
 	if (ret < 0) {
 		dev_err(&pdev->dev, "Failed to register ISR for IRQ %d\n",
 					tspi->irq);
-		goto exit_free_master;
-	}
-
-	tspi->clk = devm_clk_get(&pdev->dev, NULL);
-	if (IS_ERR(tspi->clk)) {
-		dev_err(&pdev->dev, "can not get clock\n");
-		ret = PTR_ERR(tspi->clk);
-		goto exit_free_irq;
+		goto exit_clk_disable;
 	}
 
 	tspi->rst = devm_reset_control_get(&pdev->dev, "spi");
@@ -1138,6 +1149,8 @@ exit_rx_dma_free:
 	tegra_slink_deinit_dma_param(tspi, true);
 exit_free_irq:
 	free_irq(spi_irq, tspi);
+exit_clk_disable:
+	clk_disable(tspi->clk);
 exit_free_master:
 	spi_master_put(master);
 	return ret;
@@ -1150,6 +1163,8 @@ static int tegra_slink_remove(struct pla
 
 	free_irq(tspi->irq, tspi);
 
+	clk_disable(tspi->clk);
+
 	if (tspi->tx_dma_chan)
 		tegra_slink_deinit_dma_param(tspi, false);