patch "usb: gadget: f_uac2: finalize wMaxPacketSize according to bandwidth" added to usb-next

patch "usb: gadget: f_uac2: finalize wMaxPacketSize according to bandwidth" added to usb-next

[gregkh]

This is a note to let you know that I've just added the patch titled

    usb: gadget: f_uac2: finalize wMaxPacketSize according to bandwidth

to my usb git tree which can be found at
    git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
in the usb-next branch.

The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)

The patch will also be merged in the next major kernel release
during the merge window.

If you have any questions about this process, please let me know.


>From 913e4a90b6f9687ac0f543e7b632753e4f51c441 Mon Sep 17 00:00:00 2001
From: Peter Chen <peter.chen@freescale.com>
Date: Thu, 30 Jul 2015 13:13:03 +0800
Subject: usb: gadget: f_uac2: finalize wMaxPacketSize according to bandwidth

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

Acked-by: Daniel Mack <zonque@gmail.com>
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>
Signed-off-by: Felipe Balbi <balbi@ti.com>
---
 drivers/usb/gadget/function/f_uac2.c | 31 +++++++++++++++++++++++++++++--
 1 file changed, 29 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/gadget/function/f_uac2.c b/drivers/usb/gadget/function/f_uac2.c
index 6d3eb8b00a48..b5680246d6aa 100644
--- a/drivers/usb/gadget/function/f_uac2.c
+++ b/drivers/usb/gadget/function/f_uac2.c
@@ -975,6 +975,29 @@ free_ep(struct uac2_rtd_params *prm, struct usb_ep *ep)
 			"%s:%d Error!\n", __func__, __LINE__);
 }
 
+static void set_ep_max_packet_size(const struct f_uac2_opts *uac2_opts,
+	struct usb_endpoint_descriptor *ep_desc,
+	unsigned int factor, bool is_playback)
+{
+	int chmask, srate, ssize;
+	u16 max_packet_size;
+
+	if (is_playback) {
+		chmask = uac2_opts->p_chmask;
+		srate = uac2_opts->p_srate;
+		ssize = uac2_opts->p_ssize;
+	} else {
+		chmask = uac2_opts->c_chmask;
+		srate = uac2_opts->c_srate;
+		ssize = uac2_opts->c_ssize;
+	}
+
+	max_packet_size = num_channels(chmask) * ssize *
+		DIV_ROUND_UP(srate, factor / (1 << (ep_desc->bInterval - 1)));
+	ep_desc->wMaxPacketSize = cpu_to_le16(min(max_packet_size,
+				le16_to_cpu(ep_desc->wMaxPacketSize)));
+}
+
 static int
 afunc_bind(struct usb_configuration *cfg, struct usb_function *fn)
 {
@@ -1070,10 +1093,14 @@ 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 */
+	set_ep_max_packet_size(uac2_opts, &fs_epin_desc, 1000, true);
+	set_ep_max_packet_size(uac2_opts, &fs_epout_desc, 1000, false);
+	set_ep_max_packet_size(uac2_opts, &hs_epin_desc, 8000, true);
+	set_ep_max_packet_size(uac2_opts, &hs_epout_desc, 8000, false);
+
 	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)
-- 
2.5.0