[PATCH 2/2] spi: omap2-mcspi: Idle hardware during suspend and resume

[Tony Lindgren <tony@xxxxxxxxxxx>]

We currently are calling mcspi suspend and resume without considering
that mcspi might provide resources for other device driver such as
regulators. This means resume can fail and will produce -EACCES if
errors if anything calls mcspi functions between device_prepare()
and device_complete().

To fix the issue, let's do the following changes:

1. Let's add checking for return values for pm_runtime_get calls,
   and call pm_runtime_put_noidle() on errors. Things still fail
   after this change, but at least we see something is wrong as
   we now see -EACCES errors on resume.

2. Let's use noirq level for suspend and resume as other drivers
   can still call SPI related functions on suspend and resume. This
   still won't fix the -EACCES issue, but gets us to something a bit
   saner.

3. Finally, let's modify suspend and resume to call to make sure
   the device is idled properly on suspend. We have device_prepare()
   call pm_runtime_get_noresume() that won't get released until in
   device_complete() when it calls pm_runtime_put(). So if SPI is
   still active on entering suspend, it will never get idled unless
   we add calls to pm_runtime_force_suspend() and resume. This also
   fixes the -EACCES errors on resume together with changes 1 and 2
   above.

And since we're already rewriting suspend resume functions, let's
arrange the order of suspend and resume functions to be like they
usually are with suspend first.

Signed-off-by: Tony Lindgren <tony@xxxxxxxxxxx>
---
 drivers/spi/spi-omap2-mcspi.c | 54 +++++++++++++++++++++++++++++------
 1 file changed, 46 insertions(+), 8 deletions(-)

diff --git a/drivers/spi/spi-omap2-mcspi.c b/drivers/spi/spi-omap2-mcspi.c
--- a/drivers/spi/spi-omap2-mcspi.c
+++ b/drivers/spi/spi-omap2-mcspi.c
@@ -255,6 +255,7 @@ static void omap2_mcspi_set_cs(struct spi_device *spi, bool enable)
 	if (spi->controller_state) {
 		int err = pm_runtime_get_sync(mcspi->dev);
 		if (err < 0) {
+			pm_runtime_put_noidle(mcspi->dev);
 			dev_err(mcspi->dev, "failed to get sync: %d\n", err);
 			return;
 		}
@@ -1051,8 +1052,11 @@ static int omap2_mcspi_setup(struct spi_device *spi)
 	}
 
 	ret = pm_runtime_get_sync(mcspi->dev);
-	if (ret < 0)
+	if (ret < 0) {
+		pm_runtime_put_noidle(mcspi->dev);
+
 		return ret;
+	}
 
 	ret = omap2_mcspi_setup_transfer(spi, NULL);
 	pm_runtime_mark_last_busy(mcspi->dev);
@@ -1270,8 +1274,11 @@ static int omap2_mcspi_master_setup(struct omap2_mcspi *mcspi)
 	int			ret = 0;
 
 	ret = pm_runtime_get_sync(mcspi->dev);
-	if (ret < 0)
+	if (ret < 0) {
+		pm_runtime_put_noidle(mcspi->dev);
+
 		return ret;
+	}
 
 	mcspi_write_reg(master, OMAP2_MCSPI_WAKEUPENABLE,
 			OMAP2_MCSPI_WAKEUPENABLE_WKEN);
@@ -1458,14 +1465,45 @@ static int omap2_mcspi_remove(struct platform_device *pdev)
 MODULE_ALIAS("platform:omap2_mcspi");
 
 #ifdef	CONFIG_SUSPEND
-static int omap2_mcspi_resume(struct device *dev)
+static int omap2_mcspi_suspend_noirq(struct device *dev)
 {
-	return pinctrl_pm_select_default_state(dev);
+	int error;
+
+	/*
+	 * Make sure device gets idled if other drivers call SPI
+	 * functions between device_prepare() and device_complete()
+	 */
+	error = pm_runtime_force_suspend(dev);
+	if (error < 0) {
+		dev_err(dev, "%s: force suspend failed: %i\n",
+			__func__, error);
+
+		return error;
+	}
+
+	return pinctrl_pm_select_sleep_state(dev);
 }
 
-static int omap2_mcspi_suspend(struct device *dev)
+static int omap2_mcspi_resume_noirq(struct device *dev)
 {
-	return pinctrl_pm_select_sleep_state(dev);
+	struct spi_master *master = dev_get_drvdata(dev);
+	struct omap2_mcspi *mcspi = spi_master_get_devdata(master);
+	int error;
+
+	error = pinctrl_pm_select_default_state(dev);
+	if (error)
+		dev_warn(mcspi->dev, "%s: failed to set pins: %i\n",
+			 __func__, error);
+
+	error = pm_runtime_force_resume(mcspi->dev);
+	if (error < 0) {
+		dev_warn(mcspi->dev, "%s: force resume failed: %i\n",
+			 __func__, error);
+
+		return error;
+	}
+
+	return 0;
 }
 
 #else
@@ -1474,8 +1512,8 @@ static int omap2_mcspi_suspend(struct device *dev)
 #endif
 
 static const struct dev_pm_ops omap2_mcspi_pm_ops = {
-	.resume = omap2_mcspi_resume,
-	.suspend = omap2_mcspi_suspend,
+	.suspend_noirq = omap2_mcspi_suspend_noirq,
+	.resume_noirq = omap2_mcspi_resume_noirq,
 	.runtime_resume	= omap_mcspi_runtime_resume,
 };
 
-- 
2.17.0
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