[alsa-devel] [PATCH v6] ASoC: omap-mcbsp: Add PM QoS support for McBSP to prevent glitches

[Matt Ranostay]

> On Jan 10, 2017, at 23:26, Peter Ujfalusi <peter.ujfalusi at ti.com> wrote:
> 
>> On 01/11/2017 07:46 AM, Matt Ranostay wrote:
>> 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>
>> Signed-off-by: Matt Ranostay <matt at ranostay.consulting>
>> ---
>> hanges 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
>> 
>> sound/soc/omap/mcbsp.c      |  4 ++++
>> sound/soc/omap/mcbsp.h      |  3 +++
>> sound/soc/omap/omap-mcbsp.c | 44 +++++++++++++++++++++++++++++++++++++++++++-
>> 3 files changed, 50 insertions(+), 1 deletion(-)
>> 
>> diff --git a/sound/soc/omap/mcbsp.c b/sound/soc/omap/mcbsp.c
>> index 06fec5699cc8..e1c3d21dc5ed 100644
>> --- a/sound/soc/omap/mcbsp.c
>> +++ b/sound/soc/omap/mcbsp.c
>> @@ -25,6 +25,7 @@
>> #include <linux/io.h>
>> #include <linux/slab.h>
>> #include <linux/pm_runtime.h>
>> +#include <linux/pm_qos.h>
>> 
>> #include <linux/platform_data/asoc-ti-mcbsp.h>
>> 
>> @@ -1098,6 +1099,9 @@ int omap_mcbsp_init(struct platform_device *pdev)
>> 
>> void omap_mcbsp_cleanup(struct omap_mcbsp *mcbsp)
>> {
>> +    if (pm_qos_request_active(&mcbsp->pm_qos_req))
>> +        pm_qos_remove_request(&mcbsp->pm_qos_req);
>> +
> 
> It might be better to do this in asoc_mcbsp_remove() in omap-mcbsp.c so
> the pm_qos stuff is handled within one file.

Good point will I test tomorrow esp if I have a foot of snow outside...
> 
>>    if (mcbsp->pdata->buffer_size)
>>        sysfs_remove_group(&mcbsp->dev->kobj, &additional_attr_group);
>> 
>> diff --git a/sound/soc/omap/mcbsp.h b/sound/soc/omap/mcbsp.h
>> index 61e93b1c185d..46ae1269a698 100644
>> --- a/sound/soc/omap/mcbsp.h
>> +++ b/sound/soc/omap/mcbsp.h
>> @@ -323,8 +323,11 @@ struct omap_mcbsp {
>> 
>>    unsigned int fmt;
>>    unsigned int in_freq;
>> +    unsigned int latency[2];
>>    int clk_div;
>>    int wlen;
>> +
>> +    struct pm_qos_request pm_qos_req;
>> };
>> 
>> void omap_mcbsp_config(struct omap_mcbsp *mcbsp,
>> diff --git a/sound/soc/omap/omap-mcbsp.c b/sound/soc/omap/omap-mcbsp.c
>> index d018e966e533..3814a234ef61 100644
>> --- a/sound/soc/omap/omap-mcbsp.c
>> +++ b/sound/soc/omap/omap-mcbsp.c
> 
> #include <linux/pm_qos.h> ?
> 
> 
> -- 
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