[alsa-devel] [PATCH v7] ASoC: omap-mcbsp: Add PM QoS support for McBSP to prevent glitches

[Tony Lindgren]

* Matt Ranostay <matt at ranostay.consulting> [170112 19:55]:
> We can get audio errors if hitting deeper idle states on omaps:
> 
> [alsa.c:230] error: Fatal problem with alsa output, error -5.
> [audio.c:614] error: Error in writing audio (Input/output error?)!
> 
> This seems to happen with off mode idle enabled as power for the
> whole SoC may get cut off between filling the McBSP fifo using DMA.
> While active DMA blocks deeper idle states in hardware, McBSP
> activity does not seem to do so.
> 
> Basing the QoS latency calculation on the FIFO size, threshold,
> sample rate, and channels.
> 
> Based on the original patch by Tony Lindgren
> Link: https://patchwork.kernel.org/patch/9305867/
> 
> Cc: Tony Lindgren <tony at atomide.com>
> Cc: Peter Ujfalusi <peter.ujfalusi at ti.com>
> Acked-by: Peter Ujfalusi <peter.ujfalusi at ti.com>
> Signed-off-by: Matt Ranostay <matt at ranostay.consulting>
> ---
> Changes from v1:
> * add calculations for latency per number of FIFO locations
> 
> Changes from v2:
> * add missing mcbsp.h header change
> 
> Changes from v3:
> * base the latency calculations on threshold, buffer size, sample
>   rate, and channels
> 
> Changes from v4:
> * using Peter Ujfalusi's suggestions for restoring a higher latency on
>   audio stream completion, or if not applicable remove the QoS request
> 
> Changes from v5:
> * clean up latency checking logic
> * move logic to .prepare and .shutdown to avoid functions that can sleep
> 
> Changes from v6:
> * move QoS removal to asoc_mcbsp_remove from omap_mcbsp_cleanup
> * also remove header include that is unneeded

Hmm now I'm seeing these when starting or stopping playback:

WARNING: CPU: 0 PID: 373 at kernel/power/qos.c:534 omap_mcbsp_dai_shutdown+0x6c/0x70 [snd_soc_omap_mcbsp]
pm_qos_remove_request() called for unknown object
Modules linked in: snd_soc_omap_twl4030 snd_soc_twl4030 snd_soc_omap_mcbsp evdev mwifiex_sdio mwifiex leds_gpio
 snd_soc_omap cfg80211 bq27xxx_battery_i2c leds_pca963x bq27xxx_battery led_class bq24190_charger phy_twl4030_usb omap2430 mus
 b_hdrc usbcore snd_soc_core twl4030_wdt snd_pcm_dmaengine rtc_twl snd_pcm snd_timer snd soundcore twl4030_pwrbutton pwm_twl_le
 d twl4030_keypad pwm_twl matrix_keymap omap_ssi hsi ledtrig_timer usb_f_serial usb_f_rndis usb_f_mass_storage usb_f_ecm u_ethe
 r usb_f_acm libcomposite u_serial udc_core usb_common autofs4 [last unloaded: snd_soc_omap_mcbsp]
 [   51.542541] CPU: 0 PID: 373 Comm: mpg123 Not tainted 4.10.0-rc2-next-20170109+ #751
 [   51.550231] Hardware name: Generic OMAP36xx (Flattened Device Tree)
 [   51.556579] [<c0110198>] (unwind_backtrace) from [<c010c208>] (show_stack+0x10/0x14)
 [   51.564361] [<c010c208>] (show_stack) from [<c04be0a0>] (dump_stack+0xac/0xe0)
 [   51.571655] [<c04be0a0>] (dump_stack) from [<c0137428>] (__warn+0xd8/0x104)
 [   51.578643] [<c0137428>] (__warn) from [<c0137488>] (warn_slowpath_fmt+0x34/0x44)
 [   51.586212] [<c0137488>] (warn_slowpath_fmt) from [<bf3538f4>] (omap_mcbsp_dai_shutdown+0x6c/0x70 [snd_soc_omap_mcbsp])
 [   51.597351] [<bf3538f4>] (omap_mcbsp_dai_shutdown [snd_soc_omap_mcbsp]) from [<bf11037c>] (soc_pcm_close+0xa0/0x2b8 [snd_so
 c_core])
 [   51.609497] [<bf11037c>] (soc_pcm_close [snd_soc_core]) from [<bf0d0654>] (snd_pcm_release_substream.part.13+0x48/0xac [snd
 _pcm])
 [   51.621337] [<bf0d0654>] (snd_pcm_release_substream.part.13 [snd_pcm]) from [<bf0d0764>] (snd_pcm_release+0x94/0xb4 [snd_pc
 m])
 [   51.632843] [<bf0d0764>] (snd_pcm_release [snd_pcm]) from [<c02b91d8>] (__fput+0x94/0x1e4)
 [   51.641174] [<c02b91d8>] (__fput) from [<c015b768>] (task_work_run+0xcc/0x104)
 [   51.648437] [<c015b768>] (task_work_run) from [<c010bb38>] (do_work_pending+0xbc/0xc0)
 [   51.656402] [<c010bb38>] (do_work_pending) from [<c01077c8>] (slow_work_pending+0xc/0x20)


Regards,

Tony