Patchwork i2c-designware: fix RX FIFO overrun

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Submitter Josef Ahmad
Date April 22, 2013, 2:08 p.m.
Message ID <alpine.DEB.2.02.1304221508050.31571@localhost>
Download mbox | patch
Permalink /patch/238565/
State Superseded
Headers show

Comments

Josef Ahmad - April 22, 2013, 2:08 p.m.
From a969728248c3b439dc97a69e7dac133b5efa34e7 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(-)
Wolfram Sang - April 23, 2013, 4:35 p.m.
On Mon, Apr 22, 2013 at 03:08:59PM +0100, Josef Ahmad wrote:
> From a969728248c3b439dc97a69e7dac133b5efa34e7 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>

This driver had a major cleanup meanwhile. Could you rebase your patch
on top of my for-next branch? I guess this version should make it into
stable?

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Josef Ahmad - April 23, 2013, 5:44 p.m.
> On Mon, Apr 22, 2013 at 03:08:59PM +0100, Josef Ahmad wrote:
>> From a969728248c3b439dc97a69e7dac133b5efa34e7 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>
>
> This driver had a major cleanup meanwhile. Could you rebase your patch
> on top of my for-next branch? I guess this version should make it into
> stable?
>

Hi Wolfram

This patch applies just fine on top of your i2c-embedded/for-next branch.

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Wolfram Sang - April 23, 2013, 6:27 p.m.
> > This driver had a major cleanup meanwhile. Could you rebase your patch
> > on top of my for-next branch? I guess this version should make it into
> > stable?
> >
> 
> This patch applies just fine on top of your i2c-embedded/for-next branch.

i2c-embedded? Ah, this one is outdated. Please check
git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux.git i2c/for-next.

Thanks,

   Wolfram
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Patch

diff --git a/drivers/i2c/busses/i2c-designware-core.c b/drivers/i2c/busses/i2c-designware-core.c
index 94fd818..8dbeef1 100644
--- a/drivers/i2c/busses/i2c-designware-core.c
+++ b/drivers/i2c/busses/i2c-designware-core.c
@@ -426,8 +426,14 @@  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--;
@@ -480,8 +486,10 @@  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;
@@ -539,6 +547,7 @@  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