linux-kernel - [PATCH] i2c: imx: Initialize DMA before registering I2C adapter

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Date:   Sat,  8 Jun 2019 22:56:58 -0700
From:   Andrey Smirnov <andrew.smirnov@...il.com>
To:     linux-i2c@...r.kernel.org
Cc:     Andrey Smirnov <andrew.smirnov@...il.com>,
        Chris Healy <cphealy@...il.com>,
        Wolfram Sang <wsa@...-dreams.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH] i2c: imx: Initialize DMA before registering I2C adapter

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@...il.com>
Cc: Chris Healy <cphealy@...il.com>
Cc: Wolfram Sang <wsa@...-dreams.de>
Cc: Fabio Estevam <festevam@...il.com>
Cc: NXP Linux Team <linux-imx@....com>
Cc: linux-i2c@...r.kernel.org
Cc: linux-arm-kernel@...ts.infradead.org
Cc: linux-kernel@...r.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