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

From: Laurent Pinchart
Date: Thu Apr 29 2021 - 20:37:53 EST

Hi Quanyang,

Thank you for the patch.

On Thu, Apr 29, 2021 at 02:58:21PM +0800, quanyang.wang@xxxxxxxxxxxxx wrote:
> From: Quanyang Wang <quanyang.wang@xxxxxxxxxxxxx>
>
> 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@xxxxxxxxxxxxx>
> ---
> 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.

> + goto error_irq;
> + }

This part could stay where it was, just after
devm_platform_ioremap_resource().

> +
> + 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.

> +
> 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.

> 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;
> }
>

--
Regards,

Laurent Pinchart