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Date:   Sun, 27 Dec 2020 23:44:05 -0500
From:   Paul Thomas <pthomas8589@...il.com>
To:     Dan Williams <dan.j.williams@...el.com>,
        Vinod Koul <vkoul@...nel.org>,
        Michal Simek <michal.simek@...inx.com>,
        Radhey Shyam Pandey <radhey.shyam.pandey@...inx.com>,
        Matthew Murrian <matthew.murrian@...tsi.com>,
        Romain Perier <romain.perier@...il.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Marc Ferland <ferlandm@...tus.ca>,
        Sebastian von Ohr <vonohr@...ract.com>,
        dmaengine@...r.kernel.org,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
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.

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()

Our device-tree entry looks like this:
    axi_dma_0: dma@...02000 {
        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@...02030 {
            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.

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

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