[PATCH v2] OMAP3: I2C: Errata ID i207: Clear wrong RDR interrupt

[Manjunatha GK <manjugk-l0cyMroinI0@public.gmane.org>]

Under certain rare conditions, I2C_STAT[13].RDR bit may be set
and the corresponding interrupt fire, even there is no data in
the receive FIFO, or the I2C data transfer is still ongoing.
These spurious RDR events must be ignored by the software.

This patch handles and ignores RDR spurious interrupts.

Patch tested on OMAP zoom3 board.

Signed-off-by: Manjunatha GK <manjugk-l0cyMroinI0@public.gmane.org>
Cc: linux-omap-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Cc: linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Cc: ben-linux-elnMNo+KYs3YtjvyW6yDsg@public.gmane.org
Cc: Kalliguddi, Hema <hemahk-l0cyMroinI0@public.gmane.org>
Cc: Nishanth Menon <nm-l0cyMroinI0@public.gmane.org>
---
Review comments for earlier post can be found at:
https://patchwork.kernel.org/patch/90122/

 drivers/i2c/busses/i2c-omap.c |   32 +++++++++++++++++++++++++++++++-
 1 files changed, 31 insertions(+), 1 deletions(-)

diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c
index ae6f5c1..d4ec886 100644
--- a/drivers/i2c/busses/i2c-omap.c
+++ b/drivers/i2c/busses/i2c-omap.c
@@ -733,10 +733,40 @@ complete:
 		}
 		if (stat & (OMAP_I2C_STAT_RRDY | OMAP_I2C_STAT_RDR)) {
 			u8 num_bytes = 1;
+
+			/*
+			 * I2C Errata(Errata Nos. OMAP2: 1.67, OMAP3: 1.8)
+			 * Not applicable for OMAP4.
+			 * Under certain rare conditions, RDR could be set again
+			 * when the bus is busy, then ignore the interrupt and
+			 * clear the interrupt.
+			 */
+			if ((stat & OMAP_I2C_STAT_RDR) && !cpu_is_omap44xx()) {
+				/* Step 1: If RDR is set, clear it */
+				omap_i2c_ack_stat(dev, stat & OMAP_I2C_STAT_RDR);
+
+				/* Step 2: */
+				if(!(omap_i2c_read_reg(dev, OMAP_I2C_STAT_REG)
+							& OMAP_I2C_STAT_BB)) {
+					/* Step 3: */
+					while(omap_i2c_read_reg(dev,
+						OMAP_I2C_STAT_REG)
+							& OMAP_I2C_STAT_RDR) {
+						omap_i2c_ack_stat(dev, stat
+							& OMAP_I2C_STAT_RDR);
+						dev_err(dev->dev,
+						"I2C : RDR when the bus is busy.\n");
+						continue;
+					}
+
+				}
+				else
+					return IRQ_HANDLED;
+			}
 			if (dev->fifo_size) {
 				if (stat & OMAP_I2C_STAT_RRDY)
 					num_bytes = dev->fifo_size;
-				else    /* read RXSTAT on RDR interrupt */
+				else  /* Step4: read RXSTAT on RDR interrupt */
 					num_bytes = (omap_i2c_read_reg(dev,
 							OMAP_I2C_BUFSTAT_REG)
 							>> 8) & 0x3F;
-- 
1.6.0.4