Hi all,
I am currently trying to get audio output working on a LinkIt Smart
7688 (Mediatek MT7688, MIPS) using a WM8960 codec. I am using the
OpenWrt master branch (kernel 4.4.14). The relevant sections of my
device tree look like this:
/dts-v1/;
#include "mt7628an.dtsi"
/ {
/* ... */
sound {
compatible = "simple-audio-card";
simple-audio-card,name = "Audio-I2S";
simple-audio-card,format = "i2s";
simple-audio-card,bitclock-master = <&dailink0_master>;
simple-audio-card,frame-master = <&dailink0_master>;
simple-audio-card,widgets =
"Headphone", "Headphones";
simple-audio-card,routing =
"Headphones", "HP_L",
"Headphones", "HP_R";
simple-audio-card,mclk-fs = <256>;
simple-audio-card,cpu {
sound-dai = <&i2s>;
};
dailink0_master: simple-audio-card,codec {
sound-dai = <&codec>;
};
};
};
&pinctrl {
/* ... */
i2s_pins: i2s {
i2s {
ralink,group = "i2s";
ralink,function = "i2s";
};
};
wm8960_mclk_pins: wm8960_mclk {
wm8960_mclk {
ralink,group = "refclk";
ralink,function = "reclk";
};
};
};
&i2c {
compatible = "ralink,rt2880-i2c";
status = "okay";
codec: wm8960@1a {
#sound-dai-cells = <0>;
compatible = "wlf,wm8960";
reg = <0x1a>;
wlf,shared-lrclk;
};
};
&i2s {
#sound-dai-cells = <0>;
status = "okay";
pinctrl-names = "default";
pinctrl-0 = <&i2s_pins>, <&wm8960_mclk_pins>;
};
&gdma {
status = "okay";
};
I had to manually enable the support for the MT7688 in the I2S driver
by modifying the DEPENDS variable for KernelPackage/sound-mt7620 in
target/linux/ramips/modules.mk. In the kernel configuration I had to
manually enable CONFIG_DMA_RALINK and CONFIG_SND_SIMPLE_CARD.
The drivers seem to be loading fine. The relevant dmesg lines are:
rt2880-pinmux pinctrl: request pin 4 (io4) for 10000900.i2c
rt2880-pinmux pinctrl: request pin 5 (io5) for 10000900.i2c
i2c-ralink 10000900.i2c: clock 100KHz, re-start not support
rt2880-pinmux pinctrl: request pin 0 (io0) for 10000a00.i2s
rt2880-pinmux pinctrl: request pin 1 (io1) for 10000a00.i2s
rt2880-pinmux pinctrl: request pin 2 (io2) for 10000a00.i2s
rt2880-pinmux pinctrl: request pin 3 (io3) for 10000a00.i2s
rt2880-pinmux pinctrl: request pin 36 (io36) for 10000a00.i2s
ralink-i2s 10000a00.i2s: mclk 480KHz
asoc-simple-card sound: wm8960-hifi <-> 10000a00.i2s mapping ok
When running 'alsactl init', I get:
Found hardware: "Audio-I2S" "" "" "" ""
Hardware is initialized using a generic method
However, when trying to play back sounds using madplay, I run into a
kernel BUG with the call trace:
[<871014f0>] snd_pcm_lib_default_mmap+0x30/0x48 [snd_pcm]
[<871015f0>] snd_pcm_mmap_data+0xe8/0xd8c [snd_pcm]
I traced this back to the following statements in dma_mmap_attrs:
struct dma_map_ops *ops = get_dma_ops(dev);
BUG_ON(!ops);
Here, get_dma_ops always returns NULL as CONFIG_SYS_HAS_DMA_OPS is not
defined. Now I am wondering how I could resolve this issue? Any hints
are appreciated!
Thanks, Sven
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