Re: [PATCH/RFC 0/5] R-Car Gen2 DMAC hardware descriptor list support

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Morimoto-san,

On Tuesday 22 July 2014 19:17:23 Kuninori Morimoto wrote:
> Hi Laurent
> 
> > The code has been tested by artificially lowering the maximum chunk size
> > to 4096 bytes and running dmatest, which completed sucessfully. Morimoto-
> > san, is there an easy way to test cyclic transfers with your audio driver
> > ?
>
> Thank you for your offer.
> I tested this patchset with audio DMAC (= cyclic transfer)
> but, it doesn't work for me.
> 
> First of all, this sound driver which is using cyclic transfer
> was worked well in shdma-base driver.
> I had sent audio DMA support plafrom side patches before.
> But, of course I'm happy to update sound driver side.
> 
> I will re-send my audio DMAC support patches after this email.
> 
> My troubles are...

[snip]

> 2. cyclic transfer doesn't work
> 
>    I got attached error.

[snip]

I can reproduce that, but I have this error coming up before.

[   16.207027] BUG: sleeping function called from invalid context at kernel/locking/mutex.c:103
[   16.215795] in_atomic(): 1, irqs_disabled(): 128, pid: 1319, name: aplay
[   16.222636] CPU: 0 PID: 1319 Comm: aplay Not tainted 3.16.0-rc5-02821-g12a72a3 #2501
[   16.230536] Backtrace: 
[   16.233056] [<c00121e4>] (dump_backtrace) from [<c0012598>] (show_stack+0x18/0x1c)
[   16.240778]  r6:ffffffff r5:c04aa7c0 r4:00000000 r3:00000000
[   16.246593] [<c0012580>] (show_stack) from [<c032ea84>] (dump_stack+0x8c/0xc0)
[   16.253967] [<c032e9f8>] (dump_stack) from [<c0049e98>] (__might_sleep+0xcc/0x108)
[   16.261689]  r4:e8dd2000 r3:00000093
[   16.265357] [<c0049dcc>] (__might_sleep) from [<c0332134>] (mutex_lock+0x20/0x70)
[   16.272990]  r5:00000000 r4:e900fe00
[   16.276657] [<c0332114>] (mutex_lock) from [<c01fa4dc>] (regmap_lock_mutex+0x10/0x14)
[   16.284644]  r4:e900fe00 r3:00000000
[   16.288309] [<c01fa4cc>] (regmap_lock_mutex) from [<c01fb9dc>] (regmap_update_bits+0x2c/0x64)
[   16.297009] [<c01fb9b0>] (regmap_update_bits) from [<c01fba90>] (regmap_fields_write+0x38/0x44)
[   16.305883]  r7:e8d9d990 r6:00000004 r5:00000040 r4:f0368200
[   16.311701] [<c01fba58>] (regmap_fields_write) from [<bf0ec280>] (rsnd_write+0x30/0x4c [snd_soc_rcar])
[   16.321195]  r5:e93a4c00 r4:e8d1f898
[   16.324866] [<bf0ec250>] (rsnd_write [snd_soc_rcar]) from [<bf0ec884>] (rsnd_src_set_convert_rate.isra.6+0xf8/0x144 [snd_soc_rcar])
[   16.336940] [<bf0ec78c>] (rsnd_src_set_convert_rate.isra.6 [snd_soc_rcar]) from [<bf0ec8fc>] (rsnd_src_init_gen2+0x2c/0xc4 [snd_soc_rcar])
[   16.349624]  r6:00000004 r5:e8d9d810 r4:e8d1f898 r3:bf0ec8d0
[   16.355438] [<bf0ec8d0>] (rsnd_src_init_gen2 [snd_soc_rcar]) from [<bf0ea640>] (rsnd_soc_dai_trigger+0x1cc/0x22c [snd_soc_rcar])
[   16.367236]  r5:e8d9d810 r4:e8d9d824
[   16.370916] [<bf0ea474>] (rsnd_soc_dai_trigger [snd_soc_rcar]) from [<bf0c51ec>] (soc_pcm_trigger+0xa8/0xf8 [snd_soc_core])
[   16.382271]  r10:00002000 r9:00002000 r8:e9290d00 r7:e8d9d700 r6:00000001 r5:e99fb500
[   16.390301]  r4:e8ef3810
[   16.392910] [<bf0c5144>] (soc_pcm_trigger [snd_soc_core]) from [<bf094704>] (snd_pcm_do_start+0x34/0x38 [snd_pcm])
[   16.403467]  r8:bf09e050 r7:00000000 r6:00000003 r5:e99fb500 r4:bf09e050 r3:bf0c5144
[   16.411421] [<bf0946d0>] (snd_pcm_do_start [snd_pcm]) from [<bf0941f8>] (snd_pcm_action_single+0x40/0x80 [snd_pcm])
[   16.422079] [<bf0941b8>] (snd_pcm_action_single [snd_pcm]) from [<bf09443c>] (snd_pcm_action+0xcc/0xd0 [snd_pcm])
[   16.432547]  r7:00000003 r6:e99fb5c8 r5:bf09e4c0 r4:e99fb500
[   16.438366] [<bf094370>] (snd_pcm_action [snd_pcm]) from [<bf097098>] (snd_pcm_start+0x1c/0x24 [snd_pcm])
[   16.448125]  r8:00000000 r7:e8dd2000 r6:e93a4c00 r5:bf09e4c0 r4:e99fb500 r3:00002000
[   16.456083] [<bf09707c>] (snd_pcm_start [snd_pcm]) from [<bf09b094>] (snd_pcm_lib_write1+0x40c/0x4f0 [snd_pcm])
[   16.466391] [<bf09ac88>] (snd_pcm_lib_write1 [snd_pcm]) from [<bf09b244>] (snd_pcm_lib_write+0x64/0x78 [snd_pcm])
[   16.476860]  r10:be91ea4c r9:e8dd2000 r8:e8d66488 r7:00000000 r6:0002c780 r5:00000800
[   16.484889]  r4:e99fb500
[   16.487494] [<bf09b1e0>] (snd_pcm_lib_write [snd_pcm]) from [<bf096c38>] (snd_pcm_playback_ioctl1+0x134/0x4c8 [snd_pcm])
[   16.498583]  r6:00000000 r5:be91ea4c r4:e99fb500
[   16.503330] [<bf096b04>] (snd_pcm_playback_ioctl1 [snd_pcm]) from [<bf096ffc>] (snd_pcm_playback_ioctl+0x30/0x3c [snd_pcm])
[   16.514685]  r8:e8d66488 r7:be91ea4c r6:00000004 r5:e93d3880 r4:e93d3880
[   16.521575] [<bf096fcc>] (snd_pcm_playback_ioctl [snd_pcm]) from [<c00d7c10>] (do_vfs_ioctl+0x80/0x5c8)
[   16.531163] [<c00d7b90>] (do_vfs_ioctl) from [<c00d8194>] (SyS_ioctl+0x3c/0x60)
[   16.538618]  r10:00000000 r9:e8dd2000 r8:00000004 r7:be91ea4c r6:400c4150 r5:e93d3880
[   16.546648]  r4:e93d3880
[   16.549243] [<c00d8158>] (SyS_ioctl) from [<c000f8a0>] (ret_fast_syscall+0x0/0x30)
[   16.556964]  r8:c000fa24 r7:00000036 r6:00000000 r5:0002c498 r4:0002c448 r3:be91ea4c

The rsnd_soc_dai_trigger() function takes a spinlock, making the context
atomic, which regmap doesn't like as it locks a mutex.

It might be possible to fix this by setting the fast_io field in both the
regmap_config and regmap_bus structures in sound/soc/sh/rcar/gen.c. regmap
will then use a spinlock instead of a mutex. However, even if I believe that
change makes sense and should be done, another atomic context issue will come
from the rcar-dmac driver which allocates memory in the prep_dma_cyclic
function, called by rsnd_dma_start() from rsnd_soc_dai_trigger() with the
spinlock help.

What context is the rsnd_soc_dai_trigger() function called in by the alsa
core ? If it's guaranteed to be a sleepable context, would it make sense to
replace the rsnd_priv spinlock with a mutex ?

-- 
Regards,

Laurent Pinchart