[PATCH v5 1/1] OMAP2: Spi: Force CS to be in inactive state after off-mode transition

[Gregory CLEMENT <gregory.clement@free-electrons.com>]

As request by Grant Likely, there is no more cover letter. Full changelog is following.
I am still reluctant to add this changelog in the patch description, as it adds no value to
the patch itself: when it was needed I try to updat comments or patch description.
I understand that Grant Likely would need an ack from other user as this patch fix a corner case.
Kevin Hilman made a few comments on this patch so he could add his "Ack by" or at least his "Review by".


Changelog:
* Change from v1 to v2:
Rebase on linus/master (after 2.6.37-rc1)
Do some clean-up and fix indentation on both patches
Add more explanations for patch 2

* Change from v2 to v3:
Use directly resume function of spi_master instead of using function
from spi_device as Grant Likely pointed it out.
Force this transition explicitly for each CS used by a device.

* Change from v3 to v4:
Patch clean-up according to Kevin Hilman and checkpatch.
Now force CS to be in inactive state only if it was inactive when it was
suspended.

* Change from v4 to v5:
Rebase on linus/master (after 2.6.37-rc3)
Collapse some lines as pointed by Grant Likely
Fix a spelling


== CUT HERE ==
When SPI wake up from OFF mode, CS is in the wrong state: force it to the inactive state.

During the system life, I monitored the CS behavior using a oscilloscope.
I also activated debug in omap2_mcspi, so I saw when driver disable the clocks and restore context when device is not used.
Each time the CS was in the correct state.
It was only when system was put suspend to ram with off-mode activated that on resume the CS was in wrong state( ie activated).

Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
---
 drivers/spi/omap2_mcspi.c |   33 +++++++++++++++++++++++++++++++++
 1 files changed, 33 insertions(+), 0 deletions(-)

diff --git a/drivers/spi/omap2_mcspi.c b/drivers/spi/omap2_mcspi.c
index 2a651e6..dcc024a 100644
--- a/drivers/spi/omap2_mcspi.c
+++ b/drivers/spi/omap2_mcspi.c
@@ -1305,11 +1305,44 @@ static int __exit omap2_mcspi_remove(struct platform_device *pdev)
 /* work with hotplug and coldplug */
 MODULE_ALIAS("platform:omap2_mcspi");

+#ifdef	CONFIG_PM
+/* When SPI wake up from off-mode, CS is in activate state. If it was in
+ * unactive state when driver was suspend, then force it to unactive state at
+ * wake up.
+ */
+static int omap2_mcspi_resume(struct platform_device *pdev)
+{
+	struct spi_master	*master = dev_get_drvdata(&pdev->dev);
+	struct omap2_mcspi	*mcspi = spi_master_get_devdata(master);
+	struct omap2_mcspi_cs *cs;
+
+	omap2_mcspi_enable_clocks(mcspi);
+	list_for_each_entry(cs, &omap2_mcspi_ctx[master->bus_num - 1].cs,
+			    node) {
+		if ((cs->chconf0 & OMAP2_MCSPI_CHCONF_FORCE) == 0) {
+
+			/* We need to toggle CS state for OMAP take this
+			 * change in account.
+			 */
+			MOD_REG_BIT(cs->chconf0, OMAP2_MCSPI_CHCONF_FORCE, 1);
+			__raw_writel(cs->chconf0, cs->base + OMAP2_MCSPI_CHCONF0);
+			MOD_REG_BIT(cs->chconf0, OMAP2_MCSPI_CHCONF_FORCE, 0);
+			__raw_writel(cs->chconf0, cs->base + OMAP2_MCSPI_CHCONF0);
+		}
+	}
+	omap2_mcspi_disable_clocks(mcspi);
+	return 0;
+}
+#else
+#define	omap2_mcspi_resume	NULL
+#endif
+
 static struct platform_driver omap2_mcspi_driver = {
 	.driver = {
 		.name =		"omap2_mcspi",
 		.owner =	THIS_MODULE,
 	},
+	.resume =	omap2_mcspi_resume,
 	.remove =	__exit_p(omap2_mcspi_remove),
 };
 -- 1.7.0.4