spi: tegra20-slink: explicitly enable/disable clock

BugLink: https://bugs.launchpad.net/bugs/1798770

commit 7001cab1 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@toradex.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

drivers/spi/spi-tegra20-slink.c

@@ -1063,6 +1063,24 @@ static int tegra_slink_probe(struct platform_device *pdev)
 		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 platform_device *pdev)
 	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 @@ static int tegra_slink_probe(struct platform_device *pdev)
 	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 platform_device *pdev)
 
 	free_irq(tspi->irq, tspi);
 
+	clk_disable(tspi->clk);
+
 	if (tspi->tx_dma_chan)
 		tegra_slink_deinit_dma_param(tspi, false);