On Mon, 12 Nov 2018 13:47:18 +0100,
<twischer@xxxxxxxxxxxxxx> wrote:
>
> From: Laxmi Devi <Laxmi.Devi@xxxxxxxxxxxx>
>
> These changes are required due to the kernel
> commit 07b7acb51d283d8469696c906b91f1882696a4d4
> ("ASoC: rsnd: update pointer more accurate")
>
> Issue is that snd_pcm_wait() goes back to waiting because the hw_ptr
> is not period aligned. Therefore snd_pcm_wait() will block for a longer
> time as required.
>
> With these rcar driver changes the exact position of the dma is returned.
> During snd_pcm_start they read hw_ptr as reference, and this hw_ptr
> is now not period aligned, and is a little ahead over the period while it
> is read. Therefore when the avail is calculated during snd_pcm_wait(),
> it is missing the avail_min by a few frames.
>
> An additional option hw_ptr_filter is provided to dmix configuration,
> to allow the user to configure the slave application and hw pointer
> alignment at startup
>
>
> Signed-off-by: Laxmi Devi <Laxmi.Devi@xxxxxxxxxxxx>
Please provide your own sign-off when you submitting a patch, too.
The subject line should be adjusted better to match with the change;
it's about adding an option to allow alignment of hwptr reporting.
About the changes:
the term "hw_ptr_filter" might sound confusing. IMO, this is about
the (hw)ptr alignment, not about filtering.
Also, a too long option string can easily lead to a misspell :)
After all, we do either "no" alignment, "roundup" or "rounddown", or
"auto" choice.
thanks,
Takashi
> diff --git a/src/pcm/pcm_direct.c b/src/pcm/pcm_direct.c
> index 091fd78..1ff7527 100644
> --- a/src/pcm/pcm_direct.c
> +++ b/src/pcm/pcm_direct.c
> @@ -1883,6 +1883,7 @@ int snd_pcm_direct_parse_open_conf(snd_config_t *root, snd_config_t *conf,
> rec->max_periods = 0;
> rec->var_periodsize = 0;
> rec->direct_memory_access = 1;
> + rec->hw_ptr_filter = SND_PCM_HW_PTR_FLTR_AUTO;
>
> /* read defaults */
> if (snd_config_search(root, "defaults.pcm.dmix_max_periods", &n) >= 0) {
> @@ -1924,6 +1925,28 @@ int snd_pcm_direct_parse_open_conf(snd_config_t *root, snd_config_t *conf,
> rec->ipc_perm = perm;
> continue;
> }
> + if (strcmp(id, "hw_ptr_filter") == 0) {
> + const char *str;
> + err = snd_config_get_string(n, &str);
> + if (err < 0) {
> + SNDERR("Invalid type for %s", id);
> + return -EINVAL;
> + }
> + if (strcmp(str, "min_latency_min_frame_drop") == 0)
> + rec->hw_ptr_filter = SND_PCM_HW_PTR_FLTR_MIN_LATENCY_MIN_FRAME_DROP;
> + else if (strcmp(str, "no_frame_drop") == 0)
> + rec->hw_ptr_filter = SND_PCM_HW_PTR_FLTR_NO_FRAME_DROP;
> + else if (strcmp(str, "exact_wakeup") == 0)
> + rec->hw_ptr_filter = SND_PCM_HW_PTR_FLTR_EXACT_WAKEUP;
> + else if (strcmp(str, "auto") == 0)
> + rec->hw_ptr_filter = SND_PCM_HW_PTR_FLTR_AUTO;
> + else {
> + SNDERR("The field hw_ptr_filter is invalid : %s", str);
> + return -EINVAL;
> + }
> +
> + continue;
> + }
> if (strcmp(id, "ipc_gid") == 0) {
> char *group;
> char *endp;
> diff --git a/src/pcm/pcm_direct.h b/src/pcm/pcm_direct.h
> index 582f055..bd0d0a1 100644
> --- a/src/pcm/pcm_direct.h
> +++ b/src/pcm/pcm_direct.h
> @@ -49,6 +49,13 @@ typedef void (mix_areas_u8_t)(unsigned int size,
> volatile signed int *sum, size_t dst_step,
> size_t src_step, size_t sum_step);
>
> +typedef enum snd_pcm_direct_hw_ptr_filter {
> + SND_PCM_HW_PTR_FLTR_MIN_LATENCY_MIN_FRAME_DROP = 0, /* use the hw_ptr as is and do no rounding */
> + SND_PCM_HW_PTR_FLTR_NO_FRAME_DROP = 1, /* round the slave_appl_ptr up to slave_period */
> + SND_PCM_HW_PTR_FLTR_EXACT_WAKEUP = 2, /* round slave_hw_ptr and slave_appl_ptr down to slave_period */
> + SND_PCM_HW_PTR_FLTR_AUTO = 3 /* automatic selection */
> +} snd_pcm_direct_hw_ptr_filter_t;
> +
> struct slave_params {
> snd_pcm_format_t format;
> int rate;
> @@ -159,6 +166,7 @@ struct snd_pcm_direct {
> unsigned int *bindings;
> unsigned int recoveries; /* mirror of executed recoveries on slave */
> int direct_memory_access; /* use arch-optimized buffer RW */
> + snd_pcm_direct_hw_ptr_filter_t hw_ptr_filter;
> union {
> struct {
> int shmid_sum; /* IPC global sum ring buffer memory identification */
> @@ -341,6 +349,7 @@ struct snd_pcm_direct_open_conf {
> int max_periods;
> int var_periodsize;
> int direct_memory_access;
> + snd_pcm_direct_hw_ptr_filter_t hw_ptr_filter;
> snd_config_t *slave;
> snd_config_t *bindings;
> };
> diff --git a/src/pcm/pcm_dmix.c b/src/pcm/pcm_dmix.c
> index 881154e..ad1bd90 100644
> --- a/src/pcm/pcm_dmix.c
> +++ b/src/pcm/pcm_dmix.c
> @@ -55,6 +55,9 @@ const char *_snd_module_pcm_dmix = "";
> #define STATE_RUN_PENDING 1024
> #endif
>
> +#define SEC_TO_MS 1000 /* Seconds representing in Milli seconds */
> +#define LOW_LATENCY_PERIOD_TIME 10 /* slave_period time for low latency requirements in ms */
> +
> /*
> *
> */
> @@ -560,14 +563,17 @@ static int snd_pcm_dmix_hwsync(snd_pcm_t *pcm)
> static void reset_slave_ptr(snd_pcm_t *pcm, snd_pcm_direct_t *dmix)
> {
> dmix->slave_appl_ptr = dmix->slave_hw_ptr = *dmix->spcm->hw.ptr;
> - if (pcm->buffer_size > pcm->period_size * 2)
> - return;
> - /* If we have too litte periods, better to align the start position
> - * to the period boundary so that the interrupt can be handled properly
> - * at the right time.
> - */
> - dmix->slave_appl_ptr = ((dmix->slave_appl_ptr + dmix->slave_period_size - 1)
> +
> + if (dmix->hw_ptr_filter == SND_PCM_HW_PTR_FLTR_NO_FRAME_DROP ||
> + (dmix->hw_ptr_filter == SND_PCM_HW_PTR_FLTR_AUTO &&
> + pcm->buffer_size <= pcm->period_size * 2))
> + dmix->slave_appl_ptr = ((dmix->slave_appl_ptr + dmix->slave_period_size - 1)
> / dmix->slave_period_size) * dmix->slave_period_size;
> + else if (dmix->hw_ptr_filter == SND_PCM_HW_PTR_FLTR_EXACT_WAKEUP ||
> + (dmix->hw_ptr_filter == SND_PCM_HW_PTR_FLTR_AUTO &&
> + (((dmix->slave_period_size * SEC_TO_MS) / pcm->rate) < LOW_LATENCY_PERIOD_TIME)))
> + dmix->slave_appl_ptr = dmix->slave_hw_ptr = ((dmix->slave_hw_ptr
> + / dmix->slave_period_size) * dmix->slave_period_size);
> }
>
> static int snd_pcm_dmix_reset(snd_pcm_t *pcm)
> @@ -1086,6 +1092,7 @@ int snd_pcm_dmix_open(snd_pcm_t **pcmp, const char *name,
> dmix->slowptr = opts->slowptr;
> dmix->max_periods = opts->max_periods;
> dmix->var_periodsize = opts->var_periodsize;
> + dmix->hw_ptr_filter = opts->hw_ptr_filter;
> dmix->sync_ptr = snd_pcm_dmix_sync_ptr;
> dmix->direct_memory_access = opts->direct_memory_access;
>
> @@ -1241,6 +1248,12 @@ pcm.name {
> ipc_key INT # unique IPC key
> ipc_key_add_uid BOOL # add current uid to unique IPC key
> ipc_perm INT # IPC permissions (octal, default 0600)
> + hw_ptr_filter STR # Slave application and hw pointer alignment type
> + # STR can be one of the below strings :
> + # min_latency_min_frame_drop
> + # no_frame_drop
> + # exact_wakeup
> + # auto (default)
> slave STR
> # or
> slave { # Slave definition
> @@ -1273,6 +1286,25 @@ added to the value set in <code>ipc_key</code>. This will
> avoid the confliction of the same IPC key with different users
> concurrently.
>
> +<code>hw_ptr_filter</code> specifies slave application and hw pointer alignment
> +type. By default hw_ptr_filter is auto. Below are the possible configurations :
> +- min_latency_min_frame_drop : minimal latency with minimal frames dropped at
> + startup. But wakeup of application (return from snd_pcm_wait() or poll())
> + can take up to 2 * period.
> +- no_frame_drop : It is guaranteed that all frames will be played at startup. But
> + the latency will increase upto period-1 frames.
> +- exact_wakeup : It is guaranteed that a wakeup will happen for each period and
> + frames can be written from application. But on startup upto period-1 frames
> + will be dropped.
> +- auto : Selects the best approach depending on the used period and buffer size.
> + If the application buffer size is < 2 * application period, no_frame_drop
> + will be selected to avoid under runs. If the slave_period is < 10ms we
> + could expect that there are low latency requirements. Therefore exact_wakeup
> + will be chosen to avoid long wakeup times. Such wakeup delay could otherwise
> + end up with Xruns in case of a dependency to another sound device
> + (e.g. forwarding of microphone to speaker). Else min_latency_min_frame_drop
> + will be chosen.
> +
> Note that the dmix plugin itself supports only a single configuration.
> That is, it supports only the fixed rate (default 48000), format
> (\c S16), channels (2), and period_time (125000).
> --
> 2.7.4
>
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