[PATCH v3 1/2] usb: gadget: f_uac2: finalize wMaxPacketSize according to bandwidth

[PATCH v3 1/2] usb: gadget: f_uac2: finalize wMaxPacketSize according to bandwidth

[Peter Chen]

According to USB Audio Device 2.0 Spec, Ch4.10.1.1:
wMaxPacketSize is defined as follows:
Maximum packet size this endpoint is capable of sending or receiving
when this configuration is selected.
This is determined by the audio bandwidth constraints of the endpoint.

In current code, the wMaxPacketSize is defined as the maximum packet size
for ISO endpoint, and it will let the host reserve much more space than
it really needs, so that we can't let more endpoints work together at
one frame.

We find this issue when we try to let 4 f_uac2 gadgets work together [1]
at FS connection.

[1]http://www.spinics.net/lists/linux-usb/msg123478.html

Cc: andrzej.p@samsung.com
Cc: Daniel Mack <zonque@gmail.com>
Cc: tiwai@suse.de
Cc: <stable@vger.kernel.org> #v3.18+
Cc: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Peter Chen <peter.chen@freescale.com>
---

Changes for v3:
- Consider 'bInterval' to calculate wMaxPacketSize
- playback endpoint is IN ep, and capture endpoint is OUT ep

Changes for v2:
- Using DIV_ROUND_UP to calculate max packet size

 drivers/usb/gadget/function/f_uac2.c | 33 +++++++++++++++++++++++++++++++--
 1 file changed, 31 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/gadget/function/f_uac2.c b/drivers/usb/gadget/function/f_uac2.c
index 6d3eb8b..51ca32d 100644
--- a/drivers/usb/gadget/function/f_uac2.c
+++ b/drivers/usb/gadget/function/f_uac2.c
@@ -987,6 +987,8 @@ afunc_bind(struct usb_configuration *cfg, struct usb_function *fn)
 	struct f_uac2_opts *uac2_opts;
 	struct usb_string *us;
 	int ret;
+	u16 max_packet_size;
+	struct usb_endpoint_descriptor *ep_desc;
 
 	uac2_opts = container_of(fn->fi, struct f_uac2_opts, func_inst);
 
@@ -1070,10 +1072,37 @@ afunc_bind(struct usb_configuration *cfg, struct usb_function *fn)
 	uac2->p_prm.uac2 = uac2;
 	uac2->c_prm.uac2 = uac2;
 
+	/* Calculate wMaxPacketSize according to audio bandwidth */
+	ep_desc = &fs_epin_desc;
+	max_packet_size = num_channels(uac2_opts->p_chmask) *
+		uac2_opts->p_ssize * DIV_ROUND_UP(uac2_opts->p_srate,
+			1000 / (1 << (ep_desc->bInterval - 1)));
+	ep_desc->wMaxPacketSize = min(cpu_to_le16(max_packet_size),
+				ep_desc->wMaxPacketSize);
+
+	ep_desc = &fs_epout_desc;
+	max_packet_size = num_channels(uac2_opts->c_chmask) *
+		uac2_opts->c_ssize * DIV_ROUND_UP(uac2_opts->c_srate,
+			1000 / (1 << (ep_desc->bInterval - 1)));
+	ep_desc->wMaxPacketSize = min(cpu_to_le16(max_packet_size),
+				ep_desc->wMaxPacketSize);
+
+	ep_desc = &hs_epin_desc;
+	max_packet_size = num_channels(uac2_opts->p_chmask) *
+		uac2_opts->p_ssize * DIV_ROUND_UP(uac2_opts->p_srate,
+			8000 / (1 << (ep_desc->bInterval - 1)));
+	ep_desc->wMaxPacketSize = min(cpu_to_le16(max_packet_size),
+				ep_desc->wMaxPacketSize);
+
+	ep_desc = &hs_epout_desc;
+	max_packet_size = num_channels(uac2_opts->c_chmask) *
+		uac2_opts->c_ssize * DIV_ROUND_UP(uac2_opts->c_srate,
+			8000 / (1 << (ep_desc->bInterval - 1)));
+	ep_desc->wMaxPacketSize = min(cpu_to_le16(max_packet_size),
+				ep_desc->wMaxPacketSize);
+
 	hs_epout_desc.bEndpointAddress = fs_epout_desc.bEndpointAddress;
-	hs_epout_desc.wMaxPacketSize = fs_epout_desc.wMaxPacketSize;
 	hs_epin_desc.bEndpointAddress = fs_epin_desc.bEndpointAddress;
-	hs_epin_desc.wMaxPacketSize = fs_epin_desc.wMaxPacketSize;
 
 	ret = usb_assign_descriptors(fn, fs_audio_desc, hs_audio_desc, NULL);
 	if (ret)
-- 
1.9.1

[PATCH 2/2] usb: gadget: f_uac2: fix calculation of uac2->p_interval

[Peter Chen]

The p_interval should be less if the 'bInterval' at the descriptor
is larger, eg, if 'bInterval' is 5 for HS, the p_interval should be
8000 / 16 = 500.

It fixes the patch 9bb87f16 "usb: gadget: f_uac2: send reasonably
sized packets"

Cc: Daniel Mack <zonque@gmail.com>
Cc: <stable@vger.kernel.org> #v3.18+
Signed-off-by: Peter Chen <peter.chen@freescale.com>
---
 drivers/usb/gadget/function/f_uac2.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/gadget/function/f_uac2.c b/drivers/usb/gadget/function/f_uac2.c
index 51ca32d..4bd9a8e 100644
--- a/drivers/usb/gadget/function/f_uac2.c
+++ b/drivers/usb/gadget/function/f_uac2.c
@@ -1191,14 +1191,14 @@ afunc_set_alt(struct usb_function *fn, unsigned intf, unsigned alt)
 			factor = 1000;
 		} else {
 			ep_desc = &hs_epin_desc;
-			factor = 125;
+			factor = 8000;
 		}
 
 		/* pre-compute some values for iso_complete() */
 		uac2->p_framesize = opts->p_ssize *
 				    num_channels(opts->p_chmask);
 		rate = opts->p_srate * uac2->p_framesize;
-		uac2->p_interval = (1 << (ep_desc->bInterval - 1)) * factor;
+		uac2->p_interval = factor / (1 << (ep_desc->bInterval - 1));
 		uac2->p_pktsize = min_t(unsigned int, rate / uac2->p_interval,
 					prm->max_psize);
 
-- 
1.9.1

Re: [PATCH v3 1/2] usb: gadget: f_uac2: finalize wMaxPacketSize according to bandwidth

[Daniel Mack]

On 07/27/2015 08:51 AM, Peter Chen wrote:
> According to USB Audio Device 2.0 Spec, Ch4.10.1.1:
> wMaxPacketSize is defined as follows:
> Maximum packet size this endpoint is capable of sending or receiving
> when this configuration is selected.
> This is determined by the audio bandwidth constraints of the endpoint.
> 
> In current code, the wMaxPacketSize is defined as the maximum packet size
> for ISO endpoint, and it will let the host reserve much more space than
> it really needs, so that we can't let more endpoints work together at
> one frame.
> 
> We find this issue when we try to let 4 f_uac2 gadgets work together [1]
> at FS connection.
> 
> [1]http://www.spinics.net/lists/linux-usb/msg123478.html
> 
> Cc: andrzej.p@samsung.com
> Cc: Daniel Mack <zonque@gmail.com>
> Cc: tiwai@suse.de
> Cc: <stable@vger.kernel.org> #v3.18+
> Cc: Alan Stern <stern@rowland.harvard.edu>
> Signed-off-by: Peter Chen <peter.chen@freescale.com>
> ---
> 
> Changes for v3:
> - Consider 'bInterval' to calculate wMaxPacketSize
> - playback endpoint is IN ep, and capture endpoint is OUT ep
> 
> Changes for v2:
> - Using DIV_ROUND_UP to calculate max packet size
> 
>  drivers/usb/gadget/function/f_uac2.c | 33 +++++++++++++++++++++++++++++++--
>  1 file changed, 31 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/gadget/function/f_uac2.c b/drivers/usb/gadget/function/f_uac2.c
> index 6d3eb8b..51ca32d 100644
> --- a/drivers/usb/gadget/function/f_uac2.c
> +++ b/drivers/usb/gadget/function/f_uac2.c
> @@ -987,6 +987,8 @@ afunc_bind(struct usb_configuration *cfg, struct usb_function *fn)
>  	struct f_uac2_opts *uac2_opts;
>  	struct usb_string *us;
>  	int ret;
> +	u16 max_packet_size;
> +	struct usb_endpoint_descriptor *ep_desc;
>  
>  	uac2_opts = container_of(fn->fi, struct f_uac2_opts, func_inst);
>  
> @@ -1070,10 +1072,37 @@ afunc_bind(struct usb_configuration *cfg, struct usb_function *fn)
>  	uac2->p_prm.uac2 = uac2;
>  	uac2->c_prm.uac2 = uac2;
>  
> +	/* Calculate wMaxPacketSize according to audio bandwidth */
> +	ep_desc = &fs_epin_desc;
> +	max_packet_size = num_channels(uac2_opts->p_chmask) *
> +		uac2_opts->p_ssize * DIV_ROUND_UP(uac2_opts->p_srate,
> +			1000 / (1 << (ep_desc->bInterval - 1)));
> +	ep_desc->wMaxPacketSize = min(cpu_to_le16(max_packet_size),
> +				ep_desc->wMaxPacketSize);
> +
> +	ep_desc = &fs_epout_desc;
> +	max_packet_size = num_channels(uac2_opts->c_chmask) *
> +		uac2_opts->c_ssize * DIV_ROUND_UP(uac2_opts->c_srate,
> +			1000 / (1 << (ep_desc->bInterval - 1)));
> +	ep_desc->wMaxPacketSize = min(cpu_to_le16(max_packet_size),
> +				ep_desc->wMaxPacketSize);
> +
> +	ep_desc = &hs_epin_desc;
> +	max_packet_size = num_channels(uac2_opts->p_chmask) *
> +		uac2_opts->p_ssize * DIV_ROUND_UP(uac2_opts->p_srate,
> +			8000 / (1 << (ep_desc->bInterval - 1)));
> +	ep_desc->wMaxPacketSize = min(cpu_to_le16(max_packet_size),
> +				ep_desc->wMaxPacketSize);
> +
> +	ep_desc = &hs_epout_desc;
> +	max_packet_size = num_channels(uac2_opts->c_chmask) *
> +		uac2_opts->c_ssize * DIV_ROUND_UP(uac2_opts->c_srate,
> +			8000 / (1 << (ep_desc->bInterval - 1)));
> +	ep_desc->wMaxPacketSize = min(cpu_to_le16(max_packet_size),
> +				ep_desc->wMaxPacketSize);

Basically, the same operation is repeated 4 times here. What about
factoring the code out to a helper function, so that the call site looks
like this:

  set_ep_max_packet_size(&fs_epin_desc,  uac2_opts, 1000);
  set_ep_max_packet_size(&fs_epout_desc, uac2_opts, 1000);
  set_ep_max_packet_size(&hs_epin_desc,  uac2_opts, 8000);
  set_ep_max_packet_size(&hs_epout_desc, uac2_opts, 8000);


Other than that, the patch now looks good to me!


Thanks,
Daniel



> +
>  	hs_epout_desc.bEndpointAddress = fs_epout_desc.bEndpointAddress;
> -	hs_epout_desc.wMaxPacketSize = fs_epout_desc.wMaxPacketSize;
>  	hs_epin_desc.bEndpointAddress = fs_epin_desc.bEndpointAddress;
> -	hs_epin_desc.wMaxPacketSize = fs_epin_desc.wMaxPacketSize;
>  
>  	ret = usb_assign_descriptors(fn, fs_audio_desc, hs_audio_desc, NULL);
>  	if (ret)
> 

Re: [PATCH 2/2] usb: gadget: f_uac2: fix calculation of uac2->p_interval

[Daniel Mack]

On 07/27/2015 08:51 AM, Peter Chen wrote:
> The p_interval should be less if the 'bInterval' at the descriptor
> is larger, eg, if 'bInterval' is 5 for HS, the p_interval should be
> 8000 / 16 = 500.
> 
> It fixes the patch 9bb87f16 "usb: gadget: f_uac2: send reasonably
> sized packets"
> 

Acked-by: Daniel Mack <zonque@gmail.com>


Thanks for spotting this!

Daniel


> Cc: Daniel Mack <zonque@gmail.com>
> Cc: <stable@vger.kernel.org> #v3.18+
> Signed-off-by: Peter Chen <peter.chen@freescale.com>
> ---
>  drivers/usb/gadget/function/f_uac2.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/gadget/function/f_uac2.c b/drivers/usb/gadget/function/f_uac2.c
> index 51ca32d..4bd9a8e 100644
> --- a/drivers/usb/gadget/function/f_uac2.c
> +++ b/drivers/usb/gadget/function/f_uac2.c
> @@ -1191,14 +1191,14 @@ afunc_set_alt(struct usb_function *fn, unsigned intf, unsigned alt)
>  			factor = 1000;
>  		} else {
>  			ep_desc = &hs_epin_desc;
> -			factor = 125;
> +			factor = 8000;
>  		}
>  
>  		/* pre-compute some values for iso_complete() */
>  		uac2->p_framesize = opts->p_ssize *
>  				    num_channels(opts->p_chmask);
>  		rate = opts->p_srate * uac2->p_framesize;
> -		uac2->p_interval = (1 << (ep_desc->bInterval - 1)) * factor;
> +		uac2->p_interval = factor / (1 << (ep_desc->bInterval - 1));
>  		uac2->p_pktsize = min_t(unsigned int, rate / uac2->p_interval,
>  					prm->max_psize);
>  
>