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axidma: axidma_dma.h: axidma_request_channels: 621: Unable to get slave channel 0: tx_channel. #17

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nick1chao opened this issue Mar 20, 2017 · 12 comments
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axidma: axidma_dma.h: axidma_request_channels: 621: Unable to get slave channel 0: tx_channel. #17

nick1chao opened this issue Mar 20, 2017 · 12 comments
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@nick1chao
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Hi Brandon,
I'm trying to use your driver on a zedboard, petalinux system.When i run insmod axidma.ko command to load driver,the error in the title comes up.

This is the error log:
root@dmaTest:/lib/modules/4.6.0-xilinx/extra# insmod axidma.ko
axidma: axidma_dma.h: axidma_request_channels: 621: Unable to get slave channel 0: tx_channel.
axidma: probe of axidma_chrdev@0 failed with error -38

And my device tree of dma part is:

 axidma_chrdev: axidma_chrdev@0 {
		compatible = "xlnx,axidma-chrdev";
		dmas = <&axi_dma_0 0 &axi_dma_0 1>;
		dma-names = "tx_channel", "rx_channel";
};
amba_pl: amba_pl {
	#address-cells = <1>;
	#size-cells = <1>;
	compatible = "simple-bus";
	ranges ;
	
	
	axi_dma_0: dma@40400000 {
		#dma-cells = <1>;
		clock-names = "s_axi_lite_aclk", "m_axi_sg_aclk", "m_axi_mm2s_aclk", "m_axi_s2mm_aclk";
		clocks = <&clkc 15>, <&clkc 15>, <&clkc 15>, <&clkc 15>;
		compatible = "xlnx,axi-dma-1.00.a";
		interrupt-parent = <&intc>;
		interrupts = <0 29 4 0 30 4>;
		reg = <0x40400000 0x10000>;
		xlnx,include-sg ;
		dma-mm2s-channel@40400000 {
			compatible = "xlnx,axi-dma-mm2s-channel";
			dma-channels = <0x1>;
			interrupts = <0 29 4>;
			xlnx,datawidth = <0x20>;
			xlnx,device-id = <0x0>;
		};
		dma-s2mm-channel@40400000 {
			compatible = "xlnx,axi-dma-s2mm-channel";
			dma-channels = <0x1>;
			interrupts = <0 30 4>;
			xlnx,datawidth = <0x20>;
			xlnx,device-id = <0x1>;
		};
	};
};

I didn't change anything for you driver,but where there is a problem.
Thanks for any help you can offer.
@bperez77
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bperez77 commented Mar 21, 2017 •
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I wasn't able to reproduce the problem on my end. I'm working off the branch xilinx-v2016.3 branch of the main Xilinx kernel (https://github.com/Xilinx/linux-xlnx).

Can you let me know what repository, branch, and specific commit you're using for your kernel?

@nick1chao
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Thank you for your answer.
I use the petalinux tool to generate uboot kernel and device tree.The kernel version is 4.6.0.https://www.xilinx.com/support/download/index.html/content/xilinx/en/downloadNav/embedded-design-tools.html.

I'm going to try to use the kernel version you provided.

@raffaelesury
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raffaelesury commented Mar 21, 2017 •
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Hi Nick,
I'm using a device tree generated by HSI through petalinux 2016.3 (even though I'm not using petalinux anymore as I'm using the linaro rootfs on SD card, but still using the xilinx-v2016.3 kernel nevertheless) and then adapted the pl.dtsi file to work with the driver, and I notice that you have the same address for the two channels while I have dma-s2mm-channel@40400030. The rest looks the same.
Here's my pl.dtsi:

/*
 * CAUTION: This file is automatically generated by Xilinx.
 * Version: HSI 2016.3
 * Today is: Wed Mar  8 15:25:35 2017
*/

/ {

	axidma_chrdev: axidma_chrdev@0 {
	    compatible = "xlnx,axidma-chrdev";
	    dmas = <&axi_dma_0 0 &axi_dma_0 1>;
	    dma-names = "tx_channel", "rx_channel";
	};

	amba_pl: amba_pl {
		#address-cells = <1>;
		#size-cells = <1>;
		compatible = "simple-bus";
		ranges ;
		axi_dma_0: dma@40400000 {
			#dma-cells = <1>;
			clock-names = "s_axi_lite_aclk", "m_axi_sg_aclk", "m_axi_mm2s_aclk", "m_axi_s2mm_aclk";
			clocks = <&clkc 15>, <&clkc 15>, <&clkc 15>, <&clkc 15>;
			compatible = "xlnx,axi-dma-1.00.a";
			interrupt-parent = <&intc>;
			interrupts = <0 29 4 0 30 4>;
			reg = <0x40400000 0x10000>;
			xlnx,addrwidth = <0x20>; //NB 20h = 32b
			dma-mm2s-channel@40400000 {
				compatible = "xlnx,axi-dma-mm2s-channel";
				dma-channels = <0x1>;
				interrupts = <0 29 4>;
				xlnx,datawidth = <0x20>; 
				xlnx,device-id = <0x0>;
			};
			dma-s2mm-channel@40400030 {
				compatible = "xlnx,axi-dma-s2mm-channel";
				dma-channels = <0x1>;
				interrupts = <0 30 4>;
				xlnx,datawidth = <0x20>; 
				xlnx,device-id = <0x1>;
			};
		};
	};
};

@bperez77
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bperez77 commented Mar 22, 2017 •
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Those tags after the device tree nodes are just names that are used to refer to them in debug messages, so that shouldn't matter.

Can you attach the full dmesg output? I think the issue is that the clock-names property is incorrect in your device tree. The example on the main README hasn't been updated in a while, so that's likely the issue. Change your clock names to following:

clock-names = "s_axi_lite_aclk", "m_axi_sg_aclk", "m_axi_mm2s_aclk", "m_axi_s2mm_aclk";

Which matches the entry in @raffaelesury's device tree.

@nick1chao
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Hi
Thank you for your help.
When I use the xilinx-v2016.3 kernel,it can work. I don't know why?
I locate this problem here: /driver/dma/of_dma.c

the function:

/**

  • of_dma_find_controller - Get a DMA controller in DT DMA helpers list

  • @dma_spec: pointer to DMA specifier as found in the device tree

  • Finds a DMA controller with matching device node and number for dma cells

  • in a list of registered DMA controllers. If a match is found a valid pointer

  • to the DMA data stored is retuned. A NULL pointer is returned if no match is

  • found.
    */
    static struct of_dma *of_dma_find_controller(struct of_phandle_args *dma_spec)
    {
    struct of_dma *ofdma;

    list_for_each_entry(ofdma, &of_dma_list, of_dma_controllers)

     if (ofdma->of_node == dma_spec->np)
 	return ofdma;

    pr_debug("%s: can't find DMA controller %s\n", func,
    dma_spec->np->full_name);

    return NULL;
    }

@bperez77
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Hmm that's odd. Can you attach the full output from dmesg? The error is probably somewhere in the kenel log.

@nick1chao
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nick1chao commented Mar 27, 2017 •
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Hi Brandon,
These days i use the drivers and test programs. When s2mm and mm2s connection,it can work.
But when i send the data to the PL and deal with these data and then back to PS, cannot receive data.
What reason is this?

And how i can use the interrupts for the DMA in the driver.

@bperez77
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I'm going to need more information to answer your first question. What's the nature of the error, is it hanging or crashing? What's the design you're using on the PL? What's the application that you're running? Can you attach the program output and dmesg output? The error is probably in there.

As for the interrupts, each AXI DMA/VDMA will have an interrupt port (s2mm_introut and mm2s_introut). You'll need to concatenate these signals together with a Concat IP block, and pass it into the IRQ_F2P port of the processing system IP. Bits 0 - 7 get assigned to interrupts 29 - 36 and bits 8 - 15 get assigned to interrupts 52 - 59. Then, you need to fill in the interrupts property of the device nodes appropiately.

@nick1chao
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Hi,
The PS can send data to PL. In order to test PS can receive data from PL. I changed the design of PL.
Counter count has been to write data to fifo, PS to run the application to read 12 data. I modify your program, realized the function of a DMA read only.

The application read data failed:

root@linaro-ubuntu-desktop:# ./change_read
AXI DMA File Transfer Info:
Transmit Channel: 0
Receive Channel: 1
Transmit size: 48
Receive size: 48
output= 48 49 50 51 52 53 54 55 56 57 58 59 //Initialize the data of my read buffer
...read_success_callback... //read callback
transfor time= 0.000149
recv= 41337014 49 50 51 52 53 54 55 56 57 58 59 //The read function after the data buffer

The dmesg:

Booting Linux on physical CPU 0x0
Linux version 4.9.0-xilinx (lzrobot@ubuntu) (gcc version 4.6.1 (Sourcery CodeBench Lite 2011.09-50) ) #2 7
CPU: ARMv7 Processor [413fc090] revision 0 (ARMv7), cr=18c5387d
CPU: PIPT / VIPT nonaliasing data cache, VIPT aliasing instruction cache
OF: fdt:Machine model: Zynq Zed Development Board
cma: Reserved 16 MiB at 0x1f000000
Memory policy: Data cache writealloc
On node 0 totalpages: 131072
free_area_init_node: node 0, pgdat c0931200, node_mem_map debf0000
Normal zone: 1024 pages used for memmap
Normal zone: 0 pages reserved
Normal zone: 131072 pages, LIFO batch:31
percpu: Embedded 14 pages/cpu @debc9000 s25984 r8192 d23168 u57344
pcpu-alloc: s25984 r8192 d23168 u57344 alloc=14*4096
pcpu-alloc: [0] 0 [0] 1
Built 1 zonelists in Zone order, mobility grouping on. Total pages: 130048
Kernel command line: console=ttyPS0,115200 root=/dev/mmcblk0p2 rw earlyprintk rootfstype=ext4 rootwait
PID hash table entries: 2048 (order: 1, 8192 bytes)
Dentry cache hash table entries: 65536 (order: 6, 262144 bytes)
Inode-cache hash table entries: 32768 (order: 5, 131072 bytes)
Memory: 494532K/524288K available (5120K kernel code, 199K rwdata, 1352K rodata, 1024K init, 230K bss, 13)
Virtual kernel memory layout:
vector : 0xffff0000 - 0xffff1000 ( 4 kB)
fixmap : 0xffc00000 - 0xfff00000 (3072 kB)
vmalloc : 0xe0800000 - 0xff800000 ( 496 MB)
lowmem : 0xc0000000 - 0xe0000000 ( 512 MB)
pkmap : 0xbfe00000 - 0xc0000000 ( 2 MB)
modules : 0xbf000000 - 0xbfe00000 ( 14 MB)
.text : 0xc0008000 - 0xc0600000 (6112 kB)
.init : 0xc0800000 - 0xc0900000 (1024 kB)
.data : 0xc0900000 - 0xc0931e00 ( 200 kB)
.bss : 0xc0931e00 - 0xc096b75c ( 231 kB)
Preemptible hierarchical RCU implementation.
Build-time adjustment of leaf fanout to 32.
RCU restricting CPUs from NR_CPUS=4 to nr_cpu_ids=2.
RCU: Adjusting geometry for rcu_fanout_leaf=32, nr_cpu_ids=2
NR_IRQS:16 nr_irqs:16 16
efuse mapped to e0800000
slcr mapped to e0802000
L2C: platform modifies aux control register: 0x72360000 -> 0x72760000
L2C: DT/platform modifies aux control register: 0x72360000 -> 0x72760000
L2C-310 erratum 769419 enabled
L2C-310 enabling early BRESP for Cortex-A9
L2C-310 full line of zeros enabled for Cortex-A9
L2C-310 ID prefetch enabled, offset 1 lines
L2C-310 dynamic clock gating enabled, standby mode enabled
L2C-310 cache controller enabled, 8 ways, 512 kB
L2C-310: CACHE_ID 0x410000c8, AUX_CTRL 0x76760001
zynq_clock_init: clkc starts at e0802100
Zynq clock init
sched_clock: 64 bits at 333MHz, resolution 3ns, wraps every 4398046511103ns
clocksource: arm_global_timer: mask: 0xffffffffffffffff max_cycles: 0x4ce07af025, max_idle_ns: 4407952090s
Switching to timer-based delay loop, resolution 3ns
clocksource: ttc_clocksource: mask: 0xffff max_cycles: 0xffff, max_idle_ns: 537538477 ns
timer #0 at e080a000, irq=17
Console: colour dummy device 80x30
Calibrating delay loop (skipped), value calculated using timer frequency.. 666.66 BogoMIPS (lpj=3333333)
pid_max: default: 32768 minimum: 301
Mount-cache hash table entries: 1024 (order: 0, 4096 bytes)
Mountpoint-cache hash table entries: 1024 (order: 0, 4096 bytes)
CPU: Testing write buffer coherency: ok
CPU0: thread -1, cpu 0, socket 0, mpidr 80000000
Setting up static identity map for 0x100000 - 0x100058
CPU1: thread -1, cpu 1, socket 0, mpidr 80000001
Brought up 2 CPUs
SMP: Total of 2 processors activated (1333.33 BogoMIPS).
CPU: All CPU(s) started in SVC mode.
devtmpfs: initialized
VFP support v0.3: implementor 41 architecture 3 part 30 variant 9 rev 4
clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 19112604462750000 ns
pinctrl core: initialized pinctrl subsystem
NET: Registered protocol family 16
DMA: preallocated 256 KiB pool for atomic coherent allocations
cpuidle: using governor menu
hw-breakpoint: found 5 (+1 reserved) breakpoint and 1 watchpoint registers.
hw-breakpoint: maximum watchpoint size is 4 bytes.
zynq-ocm f800c000.ocmc: ZYNQ OCM pool: 256 KiB @ 0xe0840000
zynq-pinctrl 700.pinctrl: zynq pinctrl initialized
SCSI subsystem initialized
usbcore: registered new interface driver usbfs
usbcore: registered new interface driver hub
usbcore: registered new device driver usb
media: Linux media interface: v0.10
Linux video capture interface: v2.00
pps_core: LinuxPPS API ver. 1 registered
pps_core: Software ver. 5.3.6 - Copyright 2005-2007 Rodolfo Giometti giometti@linux.it
PTP clock support registered
EDAC MC: Ver: 3.0.0
FPGA manager framework
fpga-region fpga-full: FPGA Region probed
Advanced Linux Sound Architecture Driver Initialized.
clocksource: Switched to clocksource arm_global_timer
NET: Registered protocol family 2
TCP established hash table entries: 4096 (order: 2, 16384 bytes)
TCP bind hash table entries: 4096 (order: 3, 32768 bytes)
TCP: Hash tables configured (established 4096 bind 4096)
UDP hash table entries: 256 (order: 1, 8192 bytes)
UDP-Lite hash table entries: 256 (order: 1, 8192 bytes)
NET: Registered protocol family 1
RPC: Registered named UNIX socket transport module.
RPC: Registered udp transport module.
RPC: Registered tcp transport module.
RPC: Registered tcp NFSv4.1 backchannel transport module.
PCI: CLS 0 bytes, default 64
hw perfevents: enabled with armv7_cortex_a9 PMU driver, 7 counters available
futex hash table entries: 512 (order: 3, 32768 bytes)
workingset: timestamp_bits=30 max_order=17 bucket_order=0
jffs2: version 2.2. (NAND) (SUMMARY) \xffffffc2\xffffffa9\xffffffa9 2001-2006 Red Hat, Inc.
io scheduler noop registered
io scheduler deadline registered
io scheduler cfq registered (default)
dma-pl330 f8003000.dmac: Loaded driver for PL330 DMAC-241330
dma-pl330 f8003000.dmac: DBUFF-128x8bytes Num_Chans-8 Num_Peri-4 Num_Events-16
xilinx-vdma 40400000.dma: Xilinx AXI VDMA Engine Driver Probed!!
xilinx-vdma 40410000.dma: Xilinx AXI VDMA Engine Driver Probed!!
xilinx-vdma 40420000.dma: Xilinx AXI VDMA Engine Driver Probed!!
xilinx-vdma 40430000.dma: Xilinx AXI VDMA Engine Driver Probed!!
e0001000.serial: ttyPS0 at MMIO 0xe0001000 (irq = 143, base_baud = 3125000) is a xuartps
console [ttyPS0] enabled
brd: module loaded
loop: module loaded
libphy: Fixed MDIO Bus: probed
CAN device driver interface
libphy: MACB_mii_bus: probed
macb e000b000.ethernet eth0: Cadence GEM rev 0x00020118 at 0xe000b000 irq 145 (00:0a:35:00:01:22)
Marvell 88E1510 e000b000.etherne:00: attached PHY driver [Marvell 88E1510] (mii_bus:phy_addr=e000b000.eth)
e1000e: Intel(R) PRO/1000 Network Driver - 3.2.6-k
e1000e: Copyright(c) 1999 - 2015 Intel Corporation.
ehci_hcd: USB 2.0 'Enhanced' Host Controller (EHCI) Driver
ehci-pci: EHCI PCI platform driver
usbcore: registered new interface driver usb-storage
e0002000.usb supply vbus not found, using dummy regulator
ULPI transceiver vendor/product ID 0x0451/0x1507
Found TI TUSB1210 ULPI transceiver.
ULPI integrity check: passed.
ci_hdrc ci_hdrc.0: EHCI Host Controller
ci_hdrc ci_hdrc.0: new USB bus registered, assigned bus number 1
ci_hdrc ci_hdrc.0: USB 2.0 started, EHCI 1.00
hub 1-0:1.0: USB hub found
hub 1-0:1.0: 1 port detected
mousedev: PS/2 mouse device common for all mice
i2c /dev entries driver
EDAC MC: ECC not enabled
Xilinx Zynq CpuIdle Driver started
sdhci: Secure Digital Host Controller Interface driver
sdhci: Copyright(c) Pierre Ossman
sdhci-pltfm: SDHCI platform and OF driver helper
mmc0: SDHCI controller on e0100000.sdhci [e0100000.sdhci] using DMA
ledtrig-cpu: registered to indicate activity on CPUs
usbcore: registered new interface driver usbhid
usbhid: USB HID core driver
fpga_manager fpga0: Xilinx Zynq FPGA Manager registered
NET: Registered protocol family 10
sit: IPv6, IPv4 and MPLS over IPv4 tunneling driver
NET: Registered protocol family 17
can: controller area network core (rev 20120528 abi 9)
NET: Registered protocol family 29
can: raw protocol (rev 20120528)
can: broadcast manager protocol (rev 20161123 t)
can: netlink gateway (rev 20130117) max_hops=1
Registering SWP/SWPB emulation handler
hctosys: unable to open rtc device (rtc0)
of_cfs_init
of_cfs_init: OK
ALSA device list:
mmc0: new high speed SDHC card at address 59b4
No soundcards found.
mmcblk0: mmc0:59b4 SDU1 7.34 GiB
mmcblk0: p1 p2
EXT4-fs (mmcblk0p2): mounted filesystem with ordered data mode. Opts: (null)
VFS: Mounted root (ext4 filesystem) on device 179:2.
devtmpfs: mounted
Freeing unused kernel memory: 1024K (c0800000 - c0900000)
random: fast init done
init: hwclock main process (662) terminated with status 1
init: ureadahead main process (663) terminated with status 5
udevd[745]: starting version 175
init: gator-daemon main process (746) terminated with status 1
init: bluetooth main process (1090) terminated with status 1
init: bluetooth main process ended, respawning
IPv6: ADDRCONF(NETDEV_UP): eth0: link is not ready
init: bluetooth main process (1228) terminated with status 1
init: bluetooth main process ended, respawning
init: bluetooth main process (1246) terminated with status 1
init: bluetooth main process ended, respawning
init: bluetooth main process (1268) terminated with status 1
init: bluetooth main process ended, respawning
init: udev-fallback-graphics main process (1292) terminated with status 1
init: bluetooth main process (1330) terminated with status 1
init: bluetooth main process ended, respawning
init: failsafe main process (1207) killed by TERM signal
init: bluetooth main process (1370) terminated with status 1
init: bluetooth main process ended, respawning
init: bluetooth main process (1399) terminated with status 1
init: bluetooth main process ended, respawning
init: bluetooth main process (1475) terminated with status 1
init: bluetooth main process ended, respawning
init: tty1 main process (1480) killed by TERM signal
init: bluetooth main process (1553) terminated with status 1
init: bluetooth main process ended, respawning
init: bluetooth main process (1587) terminated with status 1
init: bluetooth main process ended, respawning
init: lightdm main process (1470) terminated with status 1
init: bluetooth main process (1623) terminated with status 1
init: bluetooth main process ended, respawning
init: bluetooth main process (1660) terminated with status 1
init: bluetooth main process ended, respawning
init: bluetooth main process (1681) terminated with status 1
init: bluetooth main process ended, respawning
init: bluetooth main process (1697) terminated with status 1
init: bluetooth main process ended, respawning
init: bluetooth main process (1715) terminated with status 1
init: bluetooth respawning too fast, stopped
init: failsafe-x main process (1611) terminated with status 1
random: crng init done
axidma: loading out-of-tree module taints kernel.
axidma: axidma_dma.c: axidma_dma_init: 674: DMA: Found 1 transmit channels and 1 receive channels.
axidma: axidma_dma.c: axidma_dma_init: 676: VDMA: Found 0 transmit channels and 0 receive channels.
axidma: axidma_dma.c: axidma_dma_init: 674: DMA: Found 1 transmit channels and 1 receive channels.
axidma: axidma_dma.c: axidma_dma_init: 676: VDMA: Found 0 transmit channels and 0 receive channels.

As for the interrupts, i mean do you have any interruption function of the driver? Or do you have any information on how to write the DMA interrupt driver.
For the first time I use the DMA and do not know much about the DMA is how to transmit data at the bottom.
Thanks for you help.

@bperez77
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So aren't you receiving data back then? You have a print statement of the receive buffer after the DMA transfer. I'm not sure what the issue is there.

As for the interrupts, the driver supports interrupts; you don't need to make any modifications to it. You just need to follow the instructions as I listed in the last post.

For example, take the AXI DMA loopback example. In this case, you have one transmit and one receive channel, which each have an interrupt dedicated to them. This leads to device tree nodes for the AXI DMA nodes like follows:

axi_dma_0: axidma0@40400000 {
    #dma-cells = <1>;
    compatible = "xlnx,axi-dma", "xlnx,axi-dma-6.03.a", "xlnx,axi-dma-1.00.a";
    reg = <0x40400000 0x10000>;
    clocks = <&clkc 15>, <&clkc 15>, <&clkc 15>, <&clkc 15>;
    clock-names = "s_axi_lite_aclk", "m_axi_sg_aclk", "m_axi_mm2s_aclk", "m_axi_s2mm_aclk";    
    xlnx,include-sg;    
    xlnx,addrwidth = <32>;

    dma-mm2s-channel@40400000 {
        compatible = "xlnx,axi-dma-mm2s-channel";
        dma-channels = <1>;
        xlnx,datawidth = <64>;
        xlnx,device-id = <0>;
        interrupt-parent = <&intc>;
        interrupts = <0 29 4>;
    };
    
    dma-s2mm-channel@40400000 {
        compatible = "xlnx,axi-dma-s2mm-channel";
        dma-channels = <1>;
        xlnx,datawidth = <64>;
        xlnx,device-id = <1>;
        interrupt-parent = <&intc>;
        interrupts = <0 30 4>;
    };
};

Note the interrupts property. The second number corresponds to the interrupt number for the channel. Above, I'm assuming the MM2S interrupt is the lowest bit, and the S2MM interrupt is the next bit, leading to the interrupt values 29 and 30, respectively.

@egaznep
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egaznep commented May 28, 2019

So aren't you receiving data back then? You have a print statement of the receive buffer after the DMA transfer. I'm not sure what the issue is there.

As for the interrupts, the driver supports interrupts; you don't need to make any modifications to it. You just need to follow the instructions as I listed in the last post.

For example, take the AXI DMA loopback example. In this case, you have one transmit and one receive channel, which each have an interrupt dedicated to them. This leads to device tree nodes for the AXI DMA nodes like follows:

axi_dma_0: axidma0@40400000 {
    #dma-cells = <1>;
    compatible = "xlnx,axi-dma", "xlnx,axi-dma-6.03.a", "xlnx,axi-dma-1.00.a";
    reg = <0x40400000 0x10000>;
    clocks = <&clkc 15>, <&clkc 15>, <&clkc 15>, <&clkc 15>;
    clock-names = "s_axi_lite_aclk", "m_axi_sg_aclk", "m_axi_mm2s_aclk", "m_axi_s2mm_aclk";    
    xlnx,include-sg;    
    xlnx,addrwidth = <32>;

    dma-mm2s-channel@40400000 {
        compatible = "xlnx,axi-dma-mm2s-channel";
        dma-channels = <1>;
        xlnx,datawidth = <64>;
        xlnx,device-id = <0>;
        interrupt-parent = <&intc>;
        interrupts = <0 29 4>;
    };
    
    dma-s2mm-channel@40400000 {
        compatible = "xlnx,axi-dma-s2mm-channel";
        dma-channels = <1>;
        xlnx,datawidth = <64>;
        xlnx,device-id = <1>;
        interrupt-parent = <&intc>;
        interrupts = <0 30 4>;
    };
};

Note the interrupts property. The second number corresponds to the interrupt number for the channel. Above, I'm assuming the MM2S interrupt is the lowest bit, and the S2MM interrupt is the next bit, leading to the interrupt values 29 and 30, respectively.

I am asking to confirm, the driver does not support DMAs with single channel, right? Currently on my design I have S2MM interface only as I just require that, and I am experiencing the documented problem. If necessary I can re-configure the core so that it has both S2MM and MM2S.

@tony1121
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using kernel version 4.19.0：
have the same error ：
axidma: axidma_dma.h: axidma_request_channels: 621: Unable to get slave channel 0: tx_channel.
axidma: probe of axidma_chrdev@0 failed with error -38

solusion：
because not attach the clock info in dts file。now attatch。
&axi_dma_0{
clock-names = "s_axi_lite_aclk", "m_axi_sg_aclk", "m_axi_mm2s_aclk", "m_axi_s2mm_aclk";
clocks = <&clkc 15>, <&clkc 15>, <&clkc 15>, <&clkc 15>;
dma-channel@40400000 {
xlnx,device-id = <0x0>;
dma-channels = <1>;
};
dma-channel@40400030 {
xlnx,device-id = <0x1>;
dma-channels = <1>;
};
};

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@bperez77 @egaznep @raffaelesury @nick1chao @tony1121