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

[Peter Ujfalusi]

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.

>  	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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