Re: [PATCH] dmaengine: xilinx: dpdma: request_irq after initializing dma channels

["quanyang.wang" <quanyang.wang@windriver.com>]

Hi Laurent,

On 4/30/21 8:36 AM, Laurent Pinchart wrote:
> Hi Quanyang,
>
> Thank you for the patch.
>
> On Thu, Apr 29, 2021 at 02:58:21PM +0800, quanyang.wang@windriver.com wrote:
>> From: Quanyang Wang <quanyang.wang@windriver.com>
>>
>> In some scenarios (kdump), dpdma hardware irqs has been enabled when
>> calling request_irq in probe function, and then the dpdma irq handler
>> xilinx_dpdma_irq_handler is invoked to access xdev->chan[i]. But at
>> this moment xdev->chan[i] hasn't been initialized. So let's call the
>> request_irq after initializing dma channels to avoid kdump kernel
>> crash as below:
>>
>> [    3.696128] Unable to handle kernel NULL pointer dereference at virtual address 000000000000012c
>> [    3.696710] xilinx-zynqmp-dpdma fd4c0000.dma-controller: Xilinx DPDMA engine is probed
>> [    3.704900] Mem abort info:
>> [    3.704902]   ESR = 0x96000005
>> [    3.704905]   EC = 0x25: DABT (current EL), IL = 32 bits
>> [    3.704907]   SET = 0, FnV = 0
>> [    3.704912]   EA = 0, S1PTW = 0
>> [    3.713800] ahci-ceva fd0c0000.ahci: supply ahci not found, using dummy regulator
>> [    3.715585] Data abort info:
>> [    3.715587]   ISV = 0, ISS = 0x00000005
>> [    3.715589]   CM = 0, WnR = 0
>> [    3.715592] [000000000000012c] user address but active_mm is swapper
>> [    3.715596] Internal error: Oops: 96000005 [#1] SMP
>> [    3.715599] Modules linked in:
>> [    3.715608] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.10.0-12170-g60894882155f-dirty #77
>> [    3.723937] Hardware name: ZynqMP ZCU102 Rev1.0 (DT)
>> [    3.723942] pstate: 80000085 (Nzcv daIf -PAN -UAO -TCO BTYPE=--)
>> [    3.723956] pc : xilinx_dpdma_irq_handler+0x418/0x560
>> [    3.793049] lr : xilinx_dpdma_irq_handler+0x3d8/0x560
>> [    3.798089] sp : ffffffc01186bdf0
>> [    3.801388] x29: ffffffc01186bdf0 x28: ffffffc011836f28
>> [    3.806692] x27: ffffff8023e0ac80 x26: 0000000000000080
>> [    3.811996] x25: 0000000008000408 x24: 0000000000000003
>> [    3.817300] x23: ffffffc01186be70 x22: ffffffc011291740
>> [    3.822604] x21: 0000000000000000 x20: 0000000008000408
>> [    3.827908] x19: 0000000000000000 x18: 0000000000000010
>> [    3.833212] x17: 0000000000000000 x16: 0000000000000000
>> [    3.838516] x15: 0000000000000000 x14: ffffffc011291740
>> [    3.843820] x13: ffffffc02eb4d000 x12: 0000000034d4d91d
>> [    3.849124] x11: 0000000000000040 x10: ffffffc0112d2d48
>> [    3.854428] x9 : ffffffc0112d2d40 x8 : ffffff8021c00268
>> [    3.859732] x7 : 0000000000000000 x6 : ffffffc011836000
>> [    3.865036] x5 : 0000000000000003 x4 : 0000000000000000
>> [    3.870340] x3 : 0000000000000001 x2 : 0000000000000000
>> [    3.875644] x1 : 0000000000000000 x0 : 000000000000012c
>> [    3.880948] Call trace:
>> [    3.883382]  xilinx_dpdma_irq_handler+0x418/0x560
>> [    3.888079]  __handle_irq_event_percpu+0x5c/0x178
>> [    3.892774]  handle_irq_event_percpu+0x34/0x98
>> [    3.897210]  handle_irq_event+0x44/0xb8
>> [    3.901030]  handle_fasteoi_irq+0xd0/0x190
>> [    3.905117]  generic_handle_irq+0x30/0x48
>> [    3.909111]  __handle_domain_irq+0x64/0xc0
>> [    3.913192]  gic_handle_irq+0x78/0xa0
>> [    3.916846]  el1_irq+0xc4/0x180
>> [    3.919982]  cpuidle_enter_state+0x134/0x2f8
>> [    3.924243]  cpuidle_enter+0x38/0x50
>> [    3.927810]  call_cpuidle+0x1c/0x40
>> [    3.931290]  do_idle+0x20c/0x270
>> [    3.934502]  cpu_startup_entry+0x28/0x58
>> [    3.938410]  rest_init+0xbc/0xcc
>> [    3.941631]  arch_call_rest_init+0x10/0x1c
>> [    3.945718]  start_kernel+0x51c/0x558
>>
>> Fixes: 7cbb0c63de3f ("dmaengine: xilinx: dpdma: Add the Xilinx DisplayPort DMA engine driver")
>> Signed-off-by: Quanyang Wang <quanyang.wang@windriver.com>
>> ---
>>   drivers/dma/xilinx/xilinx_dpdma.c | 30 +++++++++++++++---------------
>>   1 file changed, 15 insertions(+), 15 deletions(-)
>>
>> diff --git a/drivers/dma/xilinx/xilinx_dpdma.c b/drivers/dma/xilinx/xilinx_dpdma.c
>> index 70b29bd079c9..0b599402c53f 100644
>> --- a/drivers/dma/xilinx/xilinx_dpdma.c
>> +++ b/drivers/dma/xilinx/xilinx_dpdma.c
>> @@ -1622,19 +1622,6 @@ static int xilinx_dpdma_probe(struct platform_device *pdev)
>>   	if (IS_ERR(xdev->reg))
>>   		return PTR_ERR(xdev->reg);
>>   
>> -	xdev->irq = platform_get_irq(pdev, 0);
>> -	if (xdev->irq < 0) {
>> -		dev_err(xdev->dev, "failed to get platform irq\n");
>> -		return xdev->irq;
>> -	}
>> -
>> -	ret = request_irq(xdev->irq, xilinx_dpdma_irq_handler, IRQF_SHARED,
>> -			  dev_name(xdev->dev), xdev);
>> -	if (ret) {
>> -		dev_err(xdev->dev, "failed to request IRQ\n");
>> -		return ret;
>> -	}
>> -
>>   	ddev = &xdev->common;
>>   	ddev->dev = &pdev->dev;
>>   
>> @@ -1688,6 +1675,19 @@ static int xilinx_dpdma_probe(struct platform_device *pdev)
>>   		goto error_of_dma;
>>   	}
>>   
>> +	xdev->irq = platform_get_irq(pdev, 0);
>> +	if (xdev->irq < 0) {
>> +		dev_err(xdev->dev, "failed to get platform irq\n");
> As reported by the kbuild bot, ret isn't initialized here.
I will fix this in V2.
>
>> +		goto error_irq;
>> +	}
> This part could stay where it was, just after
> devm_platform_ioremap_resource().
OK，I will move it back.
>
>> +
>> +	ret = request_irq(xdev->irq, xilinx_dpdma_irq_handler, IRQF_SHARED,
>> +			  dev_name(xdev->dev), xdev);
>> +	if (ret) {
>> +		dev_err(xdev->dev, "failed to request IRQ\n");
>> +		goto error_irq;
>> +	}
> Ideally we should reset the device before requesting the IRQ, to ensure
> we start in a consistent state. There doesn't seem to be any global
> reset unfortunately. Shouldn't we at least disable interrupts ? It may
> be a bit pointless though as we reenable them right below, so I suppose
> this would be OK.

Yes, we should start in a consistent and clean state. I will disable 
interrupts

and clean up registers state in V2.

>
>> +
>>   	xilinx_dpdma_enable_irq(xdev);
>>   
>>   	xilinx_dpdma_debugfs_init(xdev);
>> @@ -1696,6 +1696,8 @@ static int xilinx_dpdma_probe(struct platform_device *pdev)
>>   
>>   	return 0;
>>   
>> +error_irq:
>> +	of_dma_controller_free(pdev->dev.of_node);
> Why not free_irq() ? This change isn't described in the commit message.

I will add it in V2.

Thanks,

Quanyang

>
>>   error_of_dma:
>>   	dma_async_device_unregister(ddev);
>>   error_dma_async:
>> @@ -1704,8 +1706,6 @@ static int xilinx_dpdma_probe(struct platform_device *pdev)
>>   	for (i = 0; i < ARRAY_SIZE(xdev->chan); i++)
>>   		xilinx_dpdma_chan_remove(xdev->chan[i]);
>>   
>> -	free_irq(xdev->irq, xdev);
>> -
>>   	return ret;
>>   }
>>