RE: dmaengine : xilinx_dma two issues
From: Radhey Shyam Pandey
Date: Fri Jan 08 2021 - 02:14:50 EST
> -----Original Message-----
> From: Radhey Shyam Pandey
> Sent: Monday, January 4, 2021 10:50 AM
> To: Paul Thomas <pthomas8589@xxxxxxxxx>; Dan Williams
> <dan.j.williams@xxxxxxxxx>; Vinod Koul <vkoul@xxxxxxxxxx>; Michal Simek
> <michals@xxxxxxxxxx>; Matthew Murrian <matthew.murrian@xxxxxxxxxx>;
> Romain Perier <romain.perier@xxxxxxxxx>; Krzysztof Kozlowski
> <krzk@xxxxxxxxxx>; Marc Ferland <ferlandm@xxxxxxxxx>; Sebastian von Ohr
> <vonohr@xxxxxxxxxxx>; dmaengine@xxxxxxxxxxxxxxx; Linux ARM <linux-
> arm-kernel@xxxxxxxxxxxxxxxxxxx>; linux-kernel <linux-
> kernel@xxxxxxxxxxxxxxx>; Shravya Kumbham <shravyak@xxxxxxxxxx>; git
> <git@xxxxxxxxxx>
> Subject: RE: dmaengine : xilinx_dma two issues
>
> > -----Original Message-----
> > From: Paul Thomas <pthomas8589@xxxxxxxxx>
> > Sent: Monday, December 28, 2020 10:14 AM
> > To: Dan Williams <dan.j.williams@xxxxxxxxx>; Vinod Koul
> > <vkoul@xxxxxxxxxx>; Michal Simek <michals@xxxxxxxxxx>; Radhey Shyam
> > Pandey <radheys@xxxxxxxxxx>; Matthew Murrian
> > <matthew.murrian@xxxxxxxxxx>; Romain Perier
> <romain.perier@xxxxxxxxx>;
> > Krzysztof Kozlowski <krzk@xxxxxxxxxx>; Marc Ferland
> > <ferlandm@xxxxxxxxx>; Sebastian von Ohr <vonohr@xxxxxxxxxxx>;
> > dmaengine@xxxxxxxxxxxxxxx; Linux ARM <linux-
> > arm-kernel@xxxxxxxxxxxxxxxxxxx>; linux-kernel <linux-
> > kernel@xxxxxxxxxxxxxxx>
> > Subject: dmaengine : xilinx_dma two issues
> >
> > Hello,
> >
> > I'm trying to get the 5.10 kernel up and running for our system, and
> > I'm running into a couple of issues with xilinx_dma.
> + (Xilinx mailing list)
>
> Thanks for bringing the issues to our notice. Replies inline.
>
> >
> > First, commit 14ccf0aab46e 'dmaengine: xilinx_dma: In dma channel
> > probe fix node order dependency' breaks our usage. Before this commit a
> call to:
> > dma_request_chan(&indio_dev->dev, "axi_dma_0"); returns fine, but
> > after that commit it returns -19. The reason for this seems to be that
> > the only channel that is setup is channel 1 (chan->id is 1 in
> xilinx_dma_chan_probe()).
> > However in
> > of_dma_xilinx_xlate() chan_id is gets set to 0 (int chan_id =
> > dma_spec-
> > >args[0];), which causes the:
> > !xdev->chan[chan_id]
> > test to fail in of_dma_xilinx_xlate()
>
> What is the channel number passed in
> dmaclient DT?
Any update on this issue?
>
> dmas = <& axi_dma_0 1>
> dma-names = "axi_dma_0"
>
> >
> > Our device-tree entry looks like this:
> > axi_dma_0: dma@80002000 {
> > status = "okay";
> > #dma-cells = <1>;
> > compatible = "xlnx,axi-dma-1.00.a";
> > interrupt-parent = <&gic>;
> > interrupts = <0 89 4>;
> > reg = <0x0 0x80002000 0x0 0x1000>;
> > xlnx,addrwidth = <0x20>;
> > clocks = <&zynqmp_clk LPD_LSBUS>, <&zynqmp_clk LPD_LSBUS>,
> > <&zynqmp_clk LPD_LSBUS>, <&zynqmp_clk LPD_LSBUS>;
> > clock-names = "s_axi_lite_aclk", "m_axi_sg_aclk",
> > "m_axi_mm2s_aclk", "m_axi_s2mm_aclk";
> > dma-channel@80002030 {
> > compatible = "xlnx,axi-dma-s2mm-channel";
> > dma-channels = <0x1>;
> > interrupts = <0 89 4>;
> > xlnx,datawidth = <0x20>;
> > xlnx,device-id = <0x0>;
> > };
> > };
> >
> > This is on a 5.10.1 kernel on arm64 zynqmp hardware.
> >
> > The second issue goes a little further back to commit e81274cd6b526
> > 'dmaengine: add support to dynamic register/unregister of channels'.
> > After this commit even just removing the module 'rmmod xilinx_dma',
> > without ever using it, results in a kernel oops like this:
> > [ 37.214568] xilinx-vdma 80002000.dma: ch 0: SG disabled
> > [ 37.219807] xilinx-vdma 80002000.dma: WARN: Device release is not
> > defined so it is not safe to unbind this driver while in use
> > [ 37.231299] xilinx-vdma 80002000.dma: Xilinx AXI DMA Engine Driver
> > Probed!!
> > [ 42.100660] Unable to handle kernel paging request at virtual
> > address dead000000000108
> > [ 42.108598] Mem abort info:
> > [ 42.111393] ESR = 0x96000044
> > [ 42.114443] EC = 0x25: DABT (current EL), IL = 32 bits
> > [ 42.119744] SET = 0, FnV = 0
> > [ 42.122794] EA = 0, S1PTW = 0
> > [ 42.125918] Data abort info:
> > [ 42.128789] ISV = 0, ISS = 0x00000044
> > [ 42.132617] CM = 0, WnR = 1
> > [ 42.135577] [dead000000000108] address between user and kernel
> > address ranges
> > [ 42.142705] Internal error: Oops: 96000044 [#1] SMP
> > [ 42.147566] Modules linked in: xilinx_dma(-) clk_xlnx_clock_wizard
> > uio_pdrv_genirq
> > [ 42.155139] CPU: 1 PID: 2075 Comm: rmmod Not tainted
> > 5.10.1-00026-g3a2e6dd7a05-dirty #192
> > [ 42.163302] Hardware name: Enclustra XU5 SOM (DT)
> > [ 42.167992] pstate: 40000005 (nZcv daif -PAN -UAO -TCO BTYPE=--)
> > [ 42.173996] pc : xilinx_dma_chan_remove+0x74/0xa0 [xilinx_dma]
> > [ 42.179815] lr : xilinx_dma_chan_remove+0x70/0xa0 [xilinx_dma]
> > [ 42.185636] sp : ffffffc01112bca0
> > [ 42.188935] x29: ffffffc01112bca0 x28: ffffff80402ea640
> > [ 42.194238] x27: 0000000000000000 x26: 0000000000000000
> > [ 42.199542] x25: 0000000000000000 x24: 0000000000000000
> > [ 42.204845] x23: 0000000000000000 x22: 0000000000000000
> > [ 42.210149] x21: ffffffc0088a2028 x20: ffffff8040c08410
> > [ 42.215452] x19: ffffff80423fa480 x18: ffffffffffffffff
> > [ 42.220756] x17: 0000000000000000 x16: 0000000000000000
> > [ 42.226059] x15: ffffffc010ce88c8 x14: 0000000000000040
> > [ 42.231363] x13: ffffff0000000000 x12: ffffffffffffffff
> > [ 42.236667] x11: 0000000000000028 x10: ffffffff7fffffff
> > [ 42.241970] x9 : ffffffff00f0dfe0 x8 : 0000000000000000
> > [ 42.247273] x7 : ffffffc010da4000 x6 : 0000000000000000
> > [ 42.252577] x5 : 0000000000210d00 x4 : ffffffc010da4da0
> > [ 42.257881] x3 : ffffff80423fa578 x2 : 0000000000000000
> > [ 42.263184] x1 : dead000000000100 x0 : dead000000000122
> > [ 42.268488] Call trace:
> > [ 42.270923] xilinx_dma_chan_remove+0x74/0xa0 [xilinx_dma]
> > [ 42.276399] xilinx_dma_remove+0x3c/0x70 [xilinx_dma]
> > [ 42.281446] platform_drv_remove+0x24/0x38
> > [ 42.285530] device_release_driver_internal+0xec/0x1a8
> > [ 42.290659] driver_detach+0x64/0xd8
> > [ 42.294226] bus_remove_driver+0x58/0xb8
> > [ 42.298133] driver_unregister+0x30/0x60
> > [ 42.302048] platform_driver_unregister+0x14/0x20
> > [ 42.306744] xilinx_vdma_driver_exit+0x18/0x978 [xilinx_dma]
> > [ 42.312396] __arm64_sys_delete_module+0x1e4/0x270
> > [ 42.317178] el0_svc_common.constprop.4+0x68/0x170
> > [ 42.321959] do_el0_svc+0x70/0x90
> > [ 42.325267] el0_svc+0x14/0x20
> > [ 42.328313] el0_sync_handler+0x90/0xb8
> > [ 42.332141] el0_sync+0x158/0x180
> > [ 42.335442] Code: 95dfce29 9103c260 95de7ffb a9490261 (f9000420)
> > [ 42.341525] ---[ end trace dbd90aeb5ca71943 ]---
> >
> > So if I use the 04c2bc2bede1 (commit before 14ccf0aab46e) version of
> > xilinx_dma.c and never remove the module then it is working with the
> > 5.10.1 kernel.
>
> Ok, we will analyze this issue and report back the findings.
+ Dave
I was able to reproduce this crash on the unloading xilinx_dma module.
This is introduced due to the e81274cd6b526 mainline commit added
in the 5.6 kernel version. The crash is coming from -
xilinx_dma_chan_remove+0x74/0xa0:
__list_del at ./include/linux/list.h:112
(inlined by) __list_del_entry at./include/linux/list.h:135
(inlined by) list_del at ./include/linux/list.h:146
(inlined by) xilinx_dma_chan_remove at drivers/dma/xilinx/xilinx_dma.c:2546
Looking into e81274cd6b526 commit - It deletes channel device_node entry.
Same channel device_node entry is also deleted in xilinx_dma_chan_remove
as a result we see this crash.
@@ -993,12 +1007,22 @@ static
void __dma_async_device_channel_unregister(struct dma_device *device,
"%s called while %d clients hold a reference\n",
__func__, chan->client_count);
mutex_lock(&dma_list_mutex);
+ list_del(&chan->device_node);
+ device->chancnt--;
I will let Dave comment on the background of this change. In
dmaengine driver - we are adding channel device node entry
so deleting it in the exit path looks fine to me. Also, I checked
other dma drivers are also deleting channel device_node entry
in .remove so it likely a common problem.
>
> >
> > Hopefully, this will be clear to someone how these issues can be
> > resolved. In general we've been very happy using the xilinx dma.
> >
> > I'm not subscribed to the linux-kernel ML so if you need any further
> > info or testing just keep me in the to: list.
> >
> > thanks,
> > Paul