Re: [RESEND] i2c: imx: defer probing on dma channel request

[Laurentiu Tudor]

Hello,

Just FYI, I'm still seeing issues with the dma driver compiled _out_, 
trying to test i2c without dma support. I get the crash below in generic 
driver code later in the boot process, debug is in progress.

P.S. This is seen on an NXP LS1043A chip.

[    5.152697] Unable to handle kernel NULL pointer dereference at 
virtual address 0000000000000010
[    5.161483] Mem abort info:
[    5.164311]   ESR = 0x96000004
[    5.167407]   Exception class = DABT (current EL), IL = 32 bits
[    5.173391] device_initialize: dev = ffff800027756808
[    5.178446] usb 4-1: new SuperSpeed Gen 1 USB device number 2 using 
xhci-hcd
[    5.185489]   SET = 0, FnV = 0
[    5.188532]   EA = 0, S1PTW = 0
[    5.191676] Data abort info:
[    5.194599]   ISV = 0, ISS = 0x00000004
[    5.198476]   CM = 0, WnR = 0
[    5.201485] [0000000000000010] user address but active_mm is swapper
[    5.207894] Internal error: Oops: 96000004 [#1] PREEMPT SMP
[    5.213455] Modules linked in:
[    5.216502] CPU: 0 PID: 18 Comm: kworker/0:1 Not tainted 
5.1.0-rc2-next-20190327-00021-g7b1a4c075381-dirty #15
[    5.226489] Hardware name: LS1043A RDB Board (DT)
[    5.231189] Workqueue: events deferred_probe_work_func
[    5.236317] pstate: a0000005 (NzCv daif -PAN -UAO)
[    5.241098] pc : device_reorder_to_tail+0x13c/0x1b8
[    5.245965] lr : device_reorder_to_tail+0xd8/0x1b8
[    5.250743] sp : ffff000011823c70
[    5.254046] x29: ffff000011823c70 x28: 0000000000000000
[    5.259347] x27: ffff0000117abcd8 x26: ffff000011293a20
[    5.264649] x25: ffff00001102a000 x24: ffff00001102a708
[    5.269950] x23: ffff00001102a700 x22: ffff000010d28000
[    5.275251] x21: ffff80007393b9a0 x20: fffffffffffffff8
[    5.280552] x19: ffff80007393b8f0 x18: ffffffffffffffff
[    5.285853] x17: 0000000000000002 x16: 0000000000000000
[    5.291154] x15: ffff00001127d6c8 x14: 000000000000017e
[    5.296454] x13: 0000000000000001 x12: 0000000000000000
[    5.301755] x11: 0000000000000000 x10: 0000000000000980
[    5.307055] x9 : ffff0000118238c0 x8 : ffff800073872560
[    5.312356] x7 : ffff800073871d00 x6 : 0000000000000058
[    5.317656] x5 : 000000000000000f x4 : 0000000000000100
[    5.322957] x3 : 000080006a351000 x2 : 0991ec05b7534200
[    5.328257] x1 : fffffffffffffff8 x0 : 0000000000000000
[    5.333560] Process kworker/0:1 (pid: 18, stack limit = 
0x(____ptrval____))
[    5.340509] Call trace:
[    5.342945]  device_reorder_to_tail+0x13c/0x1b8
[    5.347466]  device_for_each_child+0x50/0xa8
[    5.351725]  device_reorder_to_tail+0xc4/0x1b8
[    5.356157]  device_pm_move_to_tail+0x34/0x50
[    5.360502]  deferred_probe_work_func+0x64/0xa0
[    5.365023]  process_one_work+0x1c8/0x320
[    5.369021]  worker_thread+0x234/0x428
[    5.372761]  kthread+0xf4/0x120
[    5.375892]  ret_from_fork+0x10/0x18
[    5.379458] Code: 911c2318 911c02f7 d0004e19 b4000274 (f9400e84)
[    5.385541] ---[ end trace ab4b151d346a8d41 ]---

---
Best Regards, Laurentiu

On 25.03.2019 19:12, Steven Price wrote:
> On 25/03/2019 15:30, laurentiu.tudor@xxxxxxx wrote:
>> From: Laurentiu Tudor <laurentiu.tudor@xxxxxxx>
>>
>> If the dma controller is not yet probed, defer i2c probe.
>> The error path in probe was slightly modified (no functional change)
> 
> There is a functional change for cases like:
> 
>> 	ret = pm_runtime_get_sync(&pdev->dev);
>> 	if (ret < 0)
>> 		goto rpm_disable;
> 
> ...as rpm_disable will no longer fall through to the call of
> clk_disable_unprepare().
> 
>> to avoid triggering this WARN_ON():
>> "cg-pll0-div1 already disabled
>> WARNING: CPU: 1 PID: 1 at drivers/clk/clk.c:828 clk_core_disable+0xa8/0xb0"
> 
> I'm also not sure how this WARN_ON was hit. i2c_imx_probe() calls
> clk_prepare_enable() which should increment the reference count. So it
> should always be possible to decrememt the enable_count. What am I missing?
> 
>> Signed-off-by: Laurentiu Tudor <laurentiu.tudor@xxxxxxx>
>> ---
>>   drivers/i2c/busses/i2c-imx.c | 21 +++++++++++++--------
>>   1 file changed, 13 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
>> index 42fed40198a0..4e34b1572756 100644
>> --- a/drivers/i2c/busses/i2c-imx.c
>> +++ b/drivers/i2c/busses/i2c-imx.c
>> @@ -1111,7 +1111,8 @@ static int i2c_imx_probe(struct platform_device *pdev)
>>   				pdev->name, i2c_imx);
>>   	if (ret) {
>>   		dev_err(&pdev->dev, "can't claim irq %d\n", irq);
>> -		goto clk_disable;
>> +		clk_disable_unprepare(i2c_imx->clk);
>> +		return ret;
>>   	}
>>   
>>   	/* Init queue */
>> @@ -1161,19 +1162,25 @@ static int i2c_imx_probe(struct platform_device *pdev)
>>   	pm_runtime_mark_last_busy(&pdev->dev);
>>   	pm_runtime_put_autosuspend(&pdev->dev);
>>   
>> +	/* Init DMA config if supported */
>> +	ret = i2c_imx_dma_request(i2c_imx, phy_addr);
>> +	if (ret) {
>> +		if (ret != -EPROBE_DEFER)
>> +			dev_info(&pdev->dev, "can't use DMA, using PIO instead.\n");
>> +		else
>> +			goto del_adapter;
>> +	}
>> +
> 
> This can be simplified by reversing the condition:
> 
> 	if (ret) {
> 		if (ret == -EPROBE_DEFER)
> 			goto del_adapter;
> 		dev_info();
> 	}
> 
> or even:
> 
> 	if (ret == -EPROBE_DEFER)
> 		goto del_adapter;
> 	else if (ret)
> 		dev_info();
> 
>>   	dev_dbg(&i2c_imx->adapter.dev, "claimed irq %d\n", irq);
>>   	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);
>>   
>> -	/* Init DMA config if supported */
>> -	ret = i2c_imx_dma_request(i2c_imx, phy_addr);
>> -	if (ret < 0)
>> -		goto clk_notifier_unregister;
>> -
>>   	dev_info(&i2c_imx->adapter.dev, "IMX I2C adapter registered\n");
>>   	return 0;   /* Return OK */
>>   
>> +del_adapter:
>> +	i2c_del_adapter(&i2c_imx->adapter);
> 
> This looks like a separate fix (previously the call to
> i2c_add_numbered_adapter() was not undone in case of later errors). It
> worth spelling this out in the commit message.
> 
> Thanks,
> 
> Steve
> 
>>   clk_notifier_unregister:
>>   	clk_notifier_unregister(i2c_imx->clk, &i2c_imx->clk_change_nb);
>>   rpm_disable:
>> @@ -1182,8 +1189,6 @@ static int i2c_imx_probe(struct platform_device *pdev)
>>   	pm_runtime_set_suspended(&pdev->dev);
>>   	pm_runtime_dont_use_autosuspend(&pdev->dev);
>>   
>> -clk_disable:
>> -	clk_disable_unprepare(i2c_imx->clk);
>>   	return ret;
>>   }
>>   
>>
>