Revert "i2c: imx: improve the error handling in i2c_imx_dma_request()"

Since commit e1ab9a46 ("i2c: imx: improve the error handling in
i2c_imx_dma_request()") when booting with the DMA driver as module (such
as CONFIG_FSL_EDMA=m) the following endless clk warnings are seen:

[  153.077831] ------------[ cut here ]------------
[  153.082528] WARNING: CPU: 0 PID: 15 at drivers/clk/clk.c:924 clk_core_disable_lock+0x18/0x24
[  153.093077] i2c0 already disabled
[  153.096416] Modules linked in:
[  153.099521] CPU: 0 PID: 15 Comm: kworker/0:1 Tainted: G        W         5.2.0+ #321
[  153.107290] Hardware name: Freescale Vybrid VF5xx/VF6xx (Device Tree)
[  153.113772] Workqueue: events deferred_probe_work_func
[  153.118979] [<c0019560>] (unwind_backtrace) from [<c0014734>] (show_stack+0x10/0x14)
[  153.126778] [<c0014734>] (show_stack) from [<c083f8dc>] (dump_stack+0x9c/0xd4)
[  153.134051] [<c083f8dc>] (dump_stack) from [<c0031154>] (__warn+0xf8/0x124)
[  153.141056] [<c0031154>] (__warn) from [<c0031248>] (warn_slowpath_fmt+0x38/0x48)
[  153.148580] [<c0031248>] (warn_slowpath_fmt) from [<c040fde0>] (clk_core_disable_lock+0x18/0x24)
[  153.157413] [<c040fde0>] (clk_core_disable_lock) from [<c058f520>] (i2c_imx_probe+0x554/0x6ec)
[  153.166076] [<c058f520>] (i2c_imx_probe) from [<c04b9178>] (platform_drv_probe+0x48/0x98)
[  153.174297] [<c04b9178>] (platform_drv_probe) from [<c04b7298>] (really_probe+0x1d8/0x2c0)
[  153.182605] [<c04b7298>] (really_probe) from [<c04b7554>] (driver_probe_device+0x5c/0x174)
[  153.190909] [<c04b7554>] (driver_probe_device) from [<c04b58c8>] (bus_for_each_drv+0x44/0x8c)
[  153.199480] [<c04b58c8>] (bus_for_each_drv) from [<c04b746c>] (__device_attach+0xa0/0x108)
[  153.207782] [<c04b746c>] (__device_attach) from [<c04b65a4>] (bus_probe_device+0x88/0x90)
[  153.215999] [<c04b65a4>] (bus_probe_device) from [<c04b6a04>] (deferred_probe_work_func+0x60/0x90)
[  153.225003] [<c04b6a04>] (deferred_probe_work_func) from [<c004f190>] (process_one_work+0x204/0x634)
[  153.234178] [<c004f190>] (process_one_work) from [<c004f618>] (worker_thread+0x20/0x484)
[  153.242315] [<c004f618>] (worker_thread) from [<c0055c2c>] (kthread+0x118/0x150)
[  153.249758] [<c0055c2c>] (kthread) from [<c00090b4>] (ret_from_fork+0x14/0x20)
[  153.257006] Exception stack(0xdde43fb0 to 0xdde43ff8)
[  153.262095] 3fa0:                                     00000000 00000000 00000000 00000000
[  153.270306] 3fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
[  153.278520] 3fe0: 00000000 00000000 00000000 00000000 00000013 00000000
[  153.285159] irq event stamp: 3323022
[  153.288787] hardirqs last  enabled at (3323021): [<c0861c4c>] _raw_spin_unlock_irq+0x24/0x2c
[  153.297261] hardirqs last disabled at (3323022): [<c040d7a0>] clk_enable_lock+0x10/0x124
[  153.305392] softirqs last  enabled at (3322092): [<c000a504>] __do_softirq+0x344/0x540
[  153.313352] softirqs last disabled at (3322081): [<c00385c0>] irq_exit+0x10c/0x128
[  153.320946] ---[ end trace a506731ccd9bd703 ]---

This endless clk warnings behaviour is well explained by Andrey Smirnov:

"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"

So revert commit e1ab9a46 ("i2c: imx: improve the error handling in
i2c_imx_dma_request()") and restore the old behaviour, in order to
avoid regressions on existing setups.

Cc: <stable@vger.kernel.org>
Reported-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Reported-by: Russell King <linux@armlinux.org.uk>
Fixes: e1ab9a46 ("i2c: imx: improve the error handling in i2c_imx_dma_request()")
Signed-off-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

drivers/i2c/busses/i2c-imx.c

@@ -273,7 +273,7 @@ static inline unsigned char imx_i2c_read_reg(struct imx_i2c_struct *i2c_imx,
 }
 
 /* Functions for DMA support */
-static int i2c_imx_dma_request(struct imx_i2c_struct *i2c_imx,
+static void i2c_imx_dma_request(struct imx_i2c_struct *i2c_imx,
 						dma_addr_t phy_addr)
 {
 	struct imx_i2c_dma *dma;
@@ -283,7 +283,7 @@ static int i2c_imx_dma_request(struct imx_i2c_struct *i2c_imx,
 
 	dma = devm_kzalloc(dev, sizeof(*dma), GFP_KERNEL);
 	if (!dma)
-		return -ENOMEM;
+		return;
 
 	dma->chan_tx = dma_request_chan(dev, "tx");
 	if (IS_ERR(dma->chan_tx)) {
@@ -328,7 +328,7 @@ static int i2c_imx_dma_request(struct imx_i2c_struct *i2c_imx,
 	dev_info(dev, "using %s (tx) and %s (rx) for DMA transfers\n",
 		dma_chan_name(dma->chan_tx), dma_chan_name(dma->chan_rx));
 
-	return 0;
+	return;
 
 fail_rx:
 	dma_release_channel(dma->chan_rx);
@@ -336,8 +336,6 @@ static int i2c_imx_dma_request(struct imx_i2c_struct *i2c_imx,
 	dma_release_channel(dma->chan_tx);
 fail_al:
 	devm_kfree(dev, dma);
-	/* return successfully if there is no dma support */
-	return ret == -ENODEV ? 0 : ret;
 }
 
 static void i2c_imx_dma_callback(void *arg)
@@ -1165,17 +1163,13 @@ static int i2c_imx_probe(struct platform_device *pdev)
 	dev_dbg(&i2c_imx->adapter.dev, "device resources: %pR\n", res);
 	dev_dbg(&i2c_imx->adapter.dev, "adapter name: \"%s\"\n",
 		i2c_imx->adapter.name);
+	dev_info(&i2c_imx->adapter.dev, "IMX I2C adapter registered\n");
 
 	/* Init DMA config if supported */
-	ret = i2c_imx_dma_request(i2c_imx, phy_addr);
-	if (ret < 0)
-		goto del_adapter;
+	i2c_imx_dma_request(i2c_imx, phy_addr);
 
-	dev_info(&i2c_imx->adapter.dev, "IMX I2C adapter registered\n");
 	return 0;   /* Return OK */
 
-del_adapter:
-	i2c_del_adapter(&i2c_imx->adapter);
 clk_notifier_unregister:
 	clk_notifier_unregister(i2c_imx->clk, &i2c_imx->clk_change_nb);
 rpm_disable: