When using DMA mode we are facing with Oops:
[  396.458157] Unable to handle kernel access to user memory without uaccess routines at virtual address 000000000000000c
[  396.469374] Oops [#1]
[  396.471839] Modules linked in:
[  396.475144] CPU: 0 PID: 114 Comm: arecord Not tainted 6.0.0-00164-g9a8eccdaf2be-dirty #68
[  396.483619] Hardware name: YMP ELCT FPGA (DT)
[  396.488156] epc : dmaengine_pcm_open+0x1d2/0x342
[  396.493227]  ra : dmaengine_pcm_open+0x1d2/0x342
[  396.498140] epc : ffffffff807fe346 ra : ffffffff807fe346 sp : ffffffc804e138f0
[  396.505602]  gp : ffffffff817bf730 tp : ffffffd8042c8ac0 t0 : 6500000000000000
[  396.513045]  t1 : 0000000000000064 t2 : 656e69676e65616d s0 : ffffffc804e13990
[  396.520477]  s1 : ffffffd801b86a18 a0 : 0000000000000026 a1 : ffffffff816920f8
[  396.527897]  a2 : 0000000000000010 a3 : fffffffffffffffe a4 : 0000000000000000
[  396.535319]  a5 : 0000000000000000 a6 : ffffffd801b87040 a7 : 0000000000000038
[  396.542740]  s2 : ffffffd801b94a00 s3 : 0000000000000000 s4 : ffffffd80427f5e8
[  396.550153]  s5 : ffffffd80427f5e8 s6 : ffffffd801b44410 s7 : fffffffffffffff5
[  396.557569]  s8 : 0000000000000800 s9 : 0000000000000001 s10: ffffffff8066d254
[  396.564978]  s11: ffffffd8059cf768 t3 : ffffffff817d5577 t4 : ffffffff817d5577
[  396.572391]  t5 : ffffffff817d5578 t6 : ffffffc804e136e8
[  396.577876] status: 0000000200000120 badaddr: 000000000000000c cause: 000000000000000d
[  396.586007] [<ffffffff806839f4>] snd_soc_component_open+0x1a/0x68
[  396.592439] [<ffffffff807fdd62>] __soc_pcm_open+0xf0/0x502
[  396.598217] [<ffffffff80685d86>] soc_pcm_open+0x2e/0x4e
[  396.603741] [<ffffffff8066cea4>] snd_pcm_open_substream+0x442/0x68e
[  396.610313] [<ffffffff8066d1ea>] snd_pcm_open+0xfa/0x212
[  396.615868] [<ffffffff8066d39c>] snd_pcm_capture_open+0x3a/0x60
[  396.622048] [<ffffffff8065b35a>] snd_open+0xa8/0x17a
[  396.627421] [<ffffffff801ae036>] chrdev_open+0xa0/0x218
[  396.632893] [<ffffffff801a5a28>] do_dentry_open+0x17c/0x2a6
[  396.638713] [<ffffffff801a6d9a>] vfs_open+0x1e/0x26
[  396.643850] [<ffffffff801b8544>] path_openat+0x96e/0xc96
[  396.649518] [<ffffffff801b9390>] do_filp_open+0x7c/0xf6
[  396.655034] [<ffffffff801a6ff2>] do_sys_openat2+0x8a/0x11e
[  396.660765] [<ffffffff801a735a>] sys_openat+0x50/0x7c
[  396.666068] [<ffffffff80003aca>] ret_from_syscall+0x0/0x2
[  396.674964] ---[ end trace 0000000000000000 ]---

It happens because of play_dma_data/capture_dma_data pointers are NULL.
Current implementation assigns these pointers at snd_soc_dai_driver
startup() callback and reset them back to NULL at shutdown(). But
soc_pcm_open() sequence uses DMA pointers in dmaengine_pcm_open()
before snd_soc_dai_driver startup().
Most generic DMA capable I2S drivers use snd_soc_dai_driver probe()
callback to init DMA pointers only once at probe. So move DMA init
to dw_i2s_dai_probe and drop shutdown() and startup() callbacks.
Signed-off-by: Maxim Kochetkov <fido_max@inbox.ru>
Link: https://lore.kernel.org/r/20230512110343.66664-1-fido_max@inbox.ruSigned-off-by: Mark Brown <broonie@kernel.org>