[alsa-devel] warnings with clk_disable_unprepare()

[Stephen Boyd]

On 12/05, Pierre-Louis Bossart wrote:
> Hi,
> In the modified cht-bsw_rt5645 machine driver for Asus X205TA and
> T100HA, I disable the audio mclk with a call to
> clk_disable_unprepare() when I see a SND_SOC_DAPM_EVENT_OFF event in
> the platform_clock_control hook.
> 
> For some reason I seem to get multiple SND_SOC_DAPM_EVENT_OFF events
> and the clock framework complains with dmesg warnings that the
> refcount is already zero (which has no functional side effect).
> 
> WARNING: CPU: 0 PID: 2002 at drivers/clk/clk.c:476 clk_unprepare+0x1a/0x21
> 
> WARNING: CPU: 2 PID: 2095 at drivers/clk/clk.c:594
> clk_core_disable_lock+0x12/0x1b
> 
> I could fix this in three different ways:
> - remove multiple SND_SOC_DAPM_EVENT_OFF events (not sure what the
> root cause is, maybe issues with jack detection?)

It would be good to know what the root cause is here before
thinking about doing anything else.

> - call a clk_is_enabled() or clk_refcount() function before calling
> clk_disable_unprepare() (but they don't seem to exist in
> include/linux/clk.h)
> - count the references myself (which does exactly the same as what
> the clk framework already does so it's not terribly elegant)
> 

Both of these sound like hacks around the problem of unbalanced
off event calls.

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