Re: [PATCH 4.4 14/19] Revert "ALSA: usb-audio: Improve frames size computation"

[Takashi Iwai <tiwai@suse.de>]

On Tue, 07 Jul 2020 17:10:17 +0200,
Greg Kroah-Hartman wrote:
> 
> From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> 
> This reverts commit 02c56650f3c118d3752122996d96173d26bb13aa which is
> commit f0bd62b64016508938df9babe47f65c2c727d25c upstream.
> 
> It causes a number of reported issues and a fix for it has not hit
> Linus's tree yet.

FYI, I'm going to send a pull request to Linus in tomorrow.
So the fix will be available in a couple of days.
Though...

> Revert this to resolve those problems.

... I'm not against the revert itself if this needs to be addressed
right now.


thanks,

Takashi

> 
> Cc: Alexander Tsoy <alexander@tsoy.me>
> Cc: Takashi Iwai <tiwai@suse.de>
> Cc: Sasha Levin <sashal@kernel.org>
> Cc: Hans de Goede <jwrdegoede@fedoraproject.org>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> ---
>  sound/usb/card.h     |    4 ----
>  sound/usb/endpoint.c |   43 +++++--------------------------------------
>  sound/usb/endpoint.h |    1 -
>  sound/usb/pcm.c      |    2 --
>  4 files changed, 5 insertions(+), 45 deletions(-)
> 
> --- a/sound/usb/card.h
> +++ b/sound/usb/card.h
> @@ -80,10 +80,6 @@ struct snd_usb_endpoint {
>  	dma_addr_t sync_dma;		/* DMA address of syncbuf */
>  
>  	unsigned int pipe;		/* the data i/o pipe */
> -	unsigned int framesize[2];	/* small/large frame sizes in samples */
> -	unsigned int sample_rem;	/* remainder from division fs/fps */
> -	unsigned int sample_accum;	/* sample accumulator */
> -	unsigned int fps;		/* frames per second */
>  	unsigned int freqn;		/* nominal sampling rate in fs/fps in Q16.16 format */
>  	unsigned int freqm;		/* momentary sampling rate in fs/fps in Q16.16 format */
>  	int	   freqshift;		/* how much to shift the feedback value to get Q16.16 */
> --- a/sound/usb/endpoint.c
> +++ b/sound/usb/endpoint.c
> @@ -137,12 +137,12 @@ int snd_usb_endpoint_implicit_feedback_s
>  
>  /*
>   * For streaming based on information derived from sync endpoints,
> - * prepare_outbound_urb_sizes() will call slave_next_packet_size() to
> + * prepare_outbound_urb_sizes() will call next_packet_size() to
>   * determine the number of samples to be sent in the next packet.
>   *
> - * For implicit feedback, slave_next_packet_size() is unused.
> + * For implicit feedback, next_packet_size() is unused.
>   */
> -int snd_usb_endpoint_slave_next_packet_size(struct snd_usb_endpoint *ep)
> +int snd_usb_endpoint_next_packet_size(struct snd_usb_endpoint *ep)
>  {
>  	unsigned long flags;
>  	int ret;
> @@ -159,29 +159,6 @@ int snd_usb_endpoint_slave_next_packet_s
>  	return ret;
>  }
>  
> -/*
> - * For adaptive and synchronous endpoints, prepare_outbound_urb_sizes()
> - * will call next_packet_size() to determine the number of samples to be
> - * sent in the next packet.
> - */
> -int snd_usb_endpoint_next_packet_size(struct snd_usb_endpoint *ep)
> -{
> -	int ret;
> -
> -	if (ep->fill_max)
> -		return ep->maxframesize;
> -
> -	ep->sample_accum += ep->sample_rem;
> -	if (ep->sample_accum >= ep->fps) {
> -		ep->sample_accum -= ep->fps;
> -		ret = ep->framesize[1];
> -	} else {
> -		ret = ep->framesize[0];
> -	}
> -
> -	return ret;
> -}
> -
>  static void retire_outbound_urb(struct snd_usb_endpoint *ep,
>  				struct snd_urb_ctx *urb_ctx)
>  {
> @@ -226,8 +203,6 @@ static void prepare_silent_urb(struct sn
>  
>  		if (ctx->packet_size[i])
>  			counts = ctx->packet_size[i];
> -		else if (ep->sync_master)
> -			counts = snd_usb_endpoint_slave_next_packet_size(ep);
>  		else
>  			counts = snd_usb_endpoint_next_packet_size(ep);
>  
> @@ -904,17 +879,10 @@ int snd_usb_endpoint_set_params(struct s
>  	ep->maxpacksize = fmt->maxpacksize;
>  	ep->fill_max = !!(fmt->attributes & UAC_EP_CS_ATTR_FILL_MAX);
>  
> -	if (snd_usb_get_speed(ep->chip->dev) == USB_SPEED_FULL) {
> +	if (snd_usb_get_speed(ep->chip->dev) == USB_SPEED_FULL)
>  		ep->freqn = get_usb_full_speed_rate(rate);
> -		ep->fps = 1000;
> -	} else {
> +	else
>  		ep->freqn = get_usb_high_speed_rate(rate);
> -		ep->fps = 8000;
> -	}
> -
> -	ep->sample_rem = rate % ep->fps;
> -	ep->framesize[0] = rate / ep->fps;
> -	ep->framesize[1] = (rate + (ep->fps - 1)) / ep->fps;
>  
>  	/* calculate the frequency in 16.16 format */
>  	ep->freqm = ep->freqn;
> @@ -973,7 +941,6 @@ int snd_usb_endpoint_start(struct snd_us
>  	ep->active_mask = 0;
>  	ep->unlink_mask = 0;
>  	ep->phase = 0;
> -	ep->sample_accum = 0;
>  
>  	snd_usb_endpoint_start_quirk(ep);
>  
> --- a/sound/usb/endpoint.h
> +++ b/sound/usb/endpoint.h
> @@ -27,7 +27,6 @@ void snd_usb_endpoint_release(struct snd
>  void snd_usb_endpoint_free(struct snd_usb_endpoint *ep);
>  
>  int snd_usb_endpoint_implicit_feedback_sink(struct snd_usb_endpoint *ep);
> -int snd_usb_endpoint_slave_next_packet_size(struct snd_usb_endpoint *ep);
>  int snd_usb_endpoint_next_packet_size(struct snd_usb_endpoint *ep);
>  
>  void snd_usb_handle_sync_urb(struct snd_usb_endpoint *ep,
> --- a/sound/usb/pcm.c
> +++ b/sound/usb/pcm.c
> @@ -1473,8 +1473,6 @@ static void prepare_playback_urb(struct
>  	for (i = 0; i < ctx->packets; i++) {
>  		if (ctx->packet_size[i])
>  			counts = ctx->packet_size[i];
> -		else if (ep->sync_master)
> -			counts = snd_usb_endpoint_slave_next_packet_size(ep);
>  		else
>  			counts = snd_usb_endpoint_next_packet_size(ep);
>  
> 
>