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Subject[PATCH] i2c: imx: Initialize DMA before registering I2C adapter
Date
Allocating DMA after registering I2C adapter can lead to infinite
probing loop, for example, consider the following scenario:

1. i2c_imx_probe() is called and successfully registers an I2C
adapter via i2c_add_numbered_adapter()

2. As a part of i2c_add_numbered_adapter() new I2C slave devices
are added from DT which results in a call to
driver_deferred_probe_trigger()

3. i2c_imx_probe() continues and calls i2c_imx_dma_request() which
due to lack of proper DMA driver returns -EPROBE_DEFER

4. i2c_imx_probe() fails, removes I2C adapter and returns
-EPROBE_DEFER, which places it into deferred probe list

5. Deferred probe work triggered in #2 above kicks in and calls
i2c_imx_probe() again thus bringing us to step #1

To avoid having this problem, move i2c_imx_dma_request() to happen
before i2c_add_numbered_adapter().

This problem was encountered on VF610 CFU1 board with
CONFIG_FSL_EDMA=n.

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Cc: Chris Healy <cphealy@gmail.com>
Cc: Wolfram Sang <wsa@the-dreams.de>
Cc: Fabio Estevam <festevam@gmail.com>
Cc: NXP Linux Team <linux-imx@nxp.com>
Cc: linux-i2c@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
---
drivers/i2c/busses/i2c-imx.c | 19 ++++++++++---------
1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
index b1b8b938d7f4..78a909f56f75 100644
--- a/drivers/i2c/busses/i2c-imx.c
+++ b/drivers/i2c/busses/i2c-imx.c
@@ -278,7 +278,7 @@ static int i2c_imx_dma_request(struct imx_i2c_struct *i2c_imx,
{
struct imx_i2c_dma *dma;
struct dma_slave_config dma_sconfig;
- struct device *dev = &i2c_imx->adapter.dev;
+ struct device *dev = i2c_imx->adapter.dev.parent;
int ret;

dma = devm_kzalloc(dev, sizeof(*dma), GFP_KERNEL);
@@ -1153,10 +1153,15 @@ static int i2c_imx_probe(struct platform_device *pdev)
if (ret == -EPROBE_DEFER)
goto clk_notifier_unregister;

+ /* Init DMA config if supported */
+ ret = i2c_imx_dma_request(i2c_imx, phy_addr);
+ if (ret < 0)
+ goto clk_notifier_unregister;
+
/* Add I2C adapter */
ret = i2c_add_numbered_adapter(&i2c_imx->adapter);
if (ret < 0)
- goto clk_notifier_unregister;
+ goto dma_free;

pm_runtime_mark_last_busy(&pdev->dev);
pm_runtime_put_autosuspend(&pdev->dev);
@@ -1166,16 +1171,12 @@ static int i2c_imx_probe(struct platform_device *pdev)
dev_dbg(&i2c_imx->adapter.dev, "adapter name: \"%s\"\n",
i2c_imx->adapter.name);

- /* Init DMA config if supported */
- ret = i2c_imx_dma_request(i2c_imx, phy_addr);
- if (ret < 0)
- goto del_adapter;
-
dev_info(&i2c_imx->adapter.dev, "IMX I2C adapter registered\n");
return 0; /* Return OK */

-del_adapter:
- i2c_del_adapter(&i2c_imx->adapter);
+dma_free:
+ if (i2c_imx->dma)
+ i2c_imx_dma_free(i2c_imx);
clk_notifier_unregister:
clk_notifier_unregister(i2c_imx->clk, &i2c_imx->clk_change_nb);
rpm_disable:
--
2.21.0
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