[PATCH] i2c: omap: fix spurious IRQs: disable/enable IRQ at INTC when idle

[Kevin Hilman <khilman-1D3HCaltpLuhEniVeURVKkEOCMrvLtNR@public.gmane.org>]

From: Kevin Hilman <khilman-l0cyMroinI0@public.gmane.org>

Currently, runtime PM is used to keep the device enabled only during
active transfers and for a configurable runtime PM autosuspend timout
after an xfer.

In addition to idling the device, driver's ->runtime_suspend() method
currently disables device interrupts when idle.  However, on some SoCs
(notably OMAP4+), the I2C hardware may shared with other coprocessors.
This means that the MPU will still recieve interrupts if a coprocessor
is using the I2C device.  To avoid this, also disable interrupts at
the MPU INTC when idling the device in ->runtime_suspend() (and
re-enable them in ->runtime_resume().)  This part based on an original
patch from Shubhrajyoti Datta.  NOTE: for proper sharing the I2C with
a coprocessor, this driver still needs hwspinlock support added.

This change is also meant to address an issue reported by Kalle
Jokiniemi where I2C bus interrupt may be enabled before an I2C device
interrupt handler (e.g. just after noirq resume phase) causing an
interrupt flood on the I2C bus interrupt before the device interrupt
is enabled (e.g. interrupts coming from devices on I2C connected PMIC
before the PMIC chained hanlder is enabled.)  This problem is addresed
by ensuring that the I2C bus interrupt left disabled until an I2C xfer
is requested.

Cc: Kalle Jokiniemi <kalle.jokiniemi-4y2FMlU5MS8onNqTyK5kxQ@public.gmane.org>
Cc: Grygorii Strashko <grygorii.strashko-l0cyMroinI0@public.gmane.org>
Cc: Shubhrajyoti Datta <shubhrajyoti-l0cyMroinI0@public.gmane.org>,
Cc: Huzefa Kankroliwala <huzefank-l0cyMroinI0@public.gmane.org>
Cc: Nishanth Menon <nm-l0cyMroinI0@public.gmane.org>
Signed-off-by: Kevin Hilman <khilman-l0cyMroinI0@public.gmane.org>
---
 drivers/i2c/busses/i2c-omap.c |    3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c
index db31eae..e6413e8 100644
--- a/drivers/i2c/busses/i2c-omap.c
+++ b/drivers/i2c/busses/i2c-omap.c
@@ -1255,6 +1255,7 @@ static int omap_i2c_runtime_suspend(struct device *dev)
 		/* Flush posted write */
 		omap_i2c_read_reg(_dev, OMAP_I2C_STAT_REG);
 	}
+	disable_irq(_dev->irq);
 
 	return 0;
 }
@@ -1275,6 +1276,8 @@ static int omap_i2c_runtime_resume(struct device *dev)
 		omap_i2c_write_reg(_dev, OMAP_I2C_CON_REG, OMAP_I2C_CON_EN);
 	}
 
+	enable_irq(_dev->irq);
+
 	/*
 	 * Don't write to this register if the IE state is 0 as it can
 	 * cause deadlock.
-- 
1.7.9.2