diff mbox

i2c-designware: fix RX FIFO overrun

Message ID alpine.DEB.2.02.1305081433430.7163@localhost
State Accepted
Headers show

Commit Message

Josef Ahmad May 8, 2013, 1:34 p.m. UTC 
From 8a4773d0c0df6fe2e816ad37fde30a2d90a1ad31 Mon Sep 17 00:00:00 2001
From: Josef Ahmad <josef.ahmad@linux.intel.com>
Date: Fri, 19 Apr 2013 17:28:10 +0100
Subject: [PATCH] i2c-designware: fix RX FIFO overrun

i2c_dw_xfer_msg() pushes a number of bytes to transmit/receive
to/from the bus into the TX FIFO.
For master-rx transactions, the maximum amount of data that can be
received is calculated depending solely on TX and RX FIFO load.

This is racy - TX FIFO may contain master-rx data yet to be
processed, which will eventually land into the RX FIFO. This
data is not taken into account and the function may request more
data than the controller is actually capable of storing.

This patch ensures the driver takes into account the outstanding
master-rx data in TX FIFO to prevent RX FIFO overrun.

Signed-off-by: Josef Ahmad <josef.ahmad@linux.intel.com>
Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
---
 drivers/i2c/busses/i2c-designware-core.c |   11 ++++++++++-
 drivers/i2c/busses/i2c-designware-core.h |    2 ++
 2 files changed, 12 insertions(+), 1 deletions(-)

Comments

Wolfram Sang May 17, 2013, 8:23 a.m. UTC | #1 
On Wed, May 08, 2013 at 02:34:36PM +0100, Josef Ahmad wrote:
> From 8a4773d0c0df6fe2e816ad37fde30a2d90a1ad31 Mon Sep 17 00:00:00 2001
> From: Josef Ahmad <josef.ahmad@linux.intel.com>
> Date: Fri, 19 Apr 2013 17:28:10 +0100
> Subject: [PATCH] i2c-designware: fix RX FIFO overrun
> 
> i2c_dw_xfer_msg() pushes a number of bytes to transmit/receive
> to/from the bus into the TX FIFO.
> For master-rx transactions, the maximum amount of data that can be
> received is calculated depending solely on TX and RX FIFO load.
> 
> This is racy - TX FIFO may contain master-rx data yet to be
> processed, which will eventually land into the RX FIFO. This
> data is not taken into account and the function may request more
> data than the controller is actually capable of storing.
> 
> This patch ensures the driver takes into account the outstanding
> master-rx data in TX FIFO to prevent RX FIFO overrun.
> 
> Signed-off-by: Josef Ahmad <josef.ahmad@linux.intel.com>
> Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>

Applied to for-current, thanks!

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Wolfram Sang May 17, 2013, 8:32 a.m. UTC | #2 
> Applied to for-current, thanks!

Added stable, too.
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Josef Ahmad May 17, 2013, 10:59 a.m. UTC | #3 
>> Applied to for-current, thanks!
>
> Added stable, too.
>

Thanks Wolfram.
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diff mbox

Patch

diff --git a/drivers/i2c/busses/i2c-designware-core.c b/drivers/i2c/busses/i2c-designware-core.c
index 21fbb34..1f06c8e 100644
--- a/drivers/i2c/busses/i2c-designware-core.c
+++ b/drivers/i2c/busses/i2c-designware-core.c
@@ -448,8 +448,14 @@  i2c_dw_xfer_msg(struct dw_i2c_dev *dev)
 				cmd |= BIT(9);

 			if (msgs[dev->msg_write_idx].flags & I2C_M_RD) {
+
+				/* avoid rx buffer overrun */
+				if (rx_limit - dev->rx_outstanding <= 0)
+					break;
+
 				dw_writel(dev, cmd | 0x100, DW_IC_DATA_CMD);
 				rx_limit--;
+				dev->rx_outstanding++;
 			} else
 				dw_writel(dev, cmd | *buf++, DW_IC_DATA_CMD);
 			tx_limit--; buf_len--;
@@ -502,8 +508,10 @@  i2c_dw_read(struct dw_i2c_dev *dev)

 		rx_valid = dw_readl(dev, DW_IC_RXFLR);

-		for (; len > 0 && rx_valid > 0; len--, rx_valid--)
+		for (; len > 0 && rx_valid > 0; len--, rx_valid--) {
 			*buf++ = dw_readl(dev, DW_IC_DATA_CMD);
+			dev->rx_outstanding--;
+		}

 		if (len > 0) {
 			dev->status |= STATUS_READ_IN_PROGRESS;
@@ -561,6 +569,7 @@  i2c_dw_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
 	dev->msg_err = 0;
 	dev->status = STATUS_IDLE;
 	dev->abort_source = 0;
+	dev->rx_outstanding = 0;

 	ret = i2c_dw_wait_bus_not_busy(dev);
 	if (ret < 0)
diff --git a/drivers/i2c/busses/i2c-designware-core.h b/drivers/i2c/busses/i2c-designware-core.h
index 9c1840e..e761ad1 100644
--- a/drivers/i2c/busses/i2c-designware-core.h
+++ b/drivers/i2c/busses/i2c-designware-core.h
@@ -60,6 +60,7 @@ 
  * @adapter: i2c subsystem adapter node
  * @tx_fifo_depth: depth of the hardware tx fifo
  * @rx_fifo_depth: depth of the hardware rx fifo
+ * @rx_outstanding: current master-rx elements in tx fifo
  */
 struct dw_i2c_dev {
 	struct device		*dev;
@@ -88,6 +89,7 @@  struct dw_i2c_dev {
 	u32			master_cfg;
 	unsigned int		tx_fifo_depth;
 	unsigned int		rx_fifo_depth;
+	int			rx_outstanding;
 };

 #define ACCESS_SWAP		0x00000001