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Revert "i2c: imx: improve the error handling in i2c_imx_dma_request()"
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Since commit e1ab9a4 ("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 GrapheneOS#2 above kicks in and calls
       i2c_imx_probe() again thus bringing us to step GrapheneOS#1"

So revert commit e1ab9a4 ("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: e1ab9a4 ("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>
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@fabioestevam
fabioestevam authored and Wolfram Sang committed Aug 14, 2019
1 parent d45331b commit e8c220f
Showing 1 changed file with 6 additions and 12 deletions.
18 changes: 6 additions & 12 deletions drivers/i2c/busses/i2c-imx.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -273,8 +273,8 @@ 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,
dma_addr_t phy_addr)
static void i2c_imx_dma_request(struct imx_i2c_struct *i2c_imx,
dma_addr_t phy_addr)
{
struct imx_i2c_dma *dma;
struct dma_slave_config dma_sconfig;
Expand All @@ -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)) {
Expand Down Expand Up @@ -328,16 +328,14 @@ 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);
fail_tx:
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)
Expand Down Expand Up @@ -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:
Expand Down

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