linux-kernel - [PATCH 3/5] i2c: omap: handle all irqs befor unblocking omap_i2c_xfer

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Date:	Fri, 7 Jun 2013 21:46:06 +0300
From:	Grygorii Strashko <grygorii.strashko@...com>
To:	Wolfram Sang <wsa@...-dreams.de>, Tony Lindgren <tony@...mide.com>
CC:	<linux-kernel@...r.kernel.org>, <linux-omap@...r.kernel.org>,
	<linux-i2c@...r.kernel.org>,
	Grygorii Strashko <grygorii.strashko@...com>,
	Kevin Hilman <khilman@...aro.org>
Subject: [PATCH 3/5] i2c: omap: handle all irqs befor unblocking omap_i2c_xfer_msg()

ARDY|NACK and ARDY|AL are set together in OMAP_I2C_STAT_REG, which will be
processed incorrectly now:
iterration 1:
- I2C irq triggered (ARDY|NACK)
- omap_i2c_isr_thread() will ask NACK, fill dev->cmd_err = OMAP_I2C_STAT_NACK
  and trigger "cmd_complete" completion.
- omap_i2c_xfer_msg() will be unblocked, hande NACK and finish its execution.
- omap_i2c_xfer() will finish

iteration 2:
- I2C irq triggered (ARDY)
- omap_i2c_isr_thread() will ask ARDY, trigger completion
  At this point dev->cmd_err == OMAP_I2C_STAT_NACK, "cmd_complete" is not
  initialized and omap_i2c_xfer() may be completed at all.

So, I2C driver is not ready for iteration 2.
Hence, fix it by asking NACK, AL and ARDY all togather in omap_i2c_isr_thread()
before unblocking omap_i2c_xfer_msg() execution.

This is the "old" I2C interrupt handler behavior which was changed by commit:
1d7afc95946487945cc7f5019b41255b72224b70 "i2c: omap: ack IRQ in parts".

CC: Kevin Hilman <khilman@...aro.org>
Signed-off-by: Grygorii Strashko <grygorii.strashko@...com>
---
 drivers/i2c/busses/i2c-omap.c |    6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c
index 2dac598..46fb8a5 100644
--- a/drivers/i2c/busses/i2c-omap.c
+++ b/drivers/i2c/busses/i2c-omap.c
@@ -938,17 +938,15 @@ omap_i2c_isr_thread(int this_irq, void *dev_id)
 			break;
 		}
 
+		omap_i2c_ack_stat(dev, OMAP_I2C_STAT_NACK | OMAP_I2C_STAT_AL);
+
 		if (stat & OMAP_I2C_STAT_NACK) {
 			err |= OMAP_I2C_STAT_NACK;
-			omap_i2c_ack_stat(dev, OMAP_I2C_STAT_NACK);
-			break;
 		}
 
 		if (stat & OMAP_I2C_STAT_AL) {
 			dev_err(dev->dev, "Arbitration lost\n");
 			err |= OMAP_I2C_STAT_AL;
-			omap_i2c_ack_stat(dev, OMAP_I2C_STAT_AL);
-			break;
 		}
 
 		/*
-- 
1.7.9.5

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