usb: gadget: f_uac2: Optionally determine bInterval for HS and SS

Allow setting configfs params p_hs_bint/c_hs_bint to 0. If they are set
to 0, determine the largest bInterval (4 to 1) for which the required
bandwidth of the max samplerate fits the max allowed packet size. If the
required bandwidth exceeds max bandwidth for single-packet mode
(ep->mc=1), keep bInterval at 1.

The FS speed is left at fixed bInterval=1.

If for any speed the required bandwidth exceeds the max bandwidth
corresponding to the selected/determined bInterval, print a warning.

Signed-off-by: Pavel Hofman <pavel.hofman@ivitera.com>
Link: https://lore.kernel.org/r/20220127114331.41367-4-pavel.hofman@ivitera.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2 files changed, 87 insertions, 43 deletions

diff --git a/drivers/usb/gadget/function/f_uac2.c b/drivers/usb/gadget/function/f_uac2.c
index 34bb6c9a9023..48d6fb26bb19 100644
--- a/drivers/usb/gadget/function/f_uac2.c
+++ b/drivers/usb/gadget/function/f_uac2.c
@@ -664,29 +664,11 @@ static int get_max_srate(const int *srates)
 	return max_srate;
 }
 
-static int set_ep_max_packet_size(const struct f_uac2_opts *uac2_opts,
-	struct usb_endpoint_descriptor *ep_desc,
-	enum usb_device_speed speed, bool is_playback)
+static int get_max_bw_for_bint(const struct f_uac2_opts *uac2_opts,
+	u8 bint, unsigned int factor, bool is_playback)
 {
 	int chmask, srate, ssize;
-	u16 max_size_bw, max_size_ep;
-	unsigned int factor;
-
-	switch (speed) {
-	case USB_SPEED_FULL:
-		max_size_ep = 1023;
-		factor = 1000;
-		break;
-
-	case USB_SPEED_HIGH:
-	case USB_SPEED_SUPER:
-		max_size_ep = 1024;
-		factor = 8000;
-		break;
-
-	default:
-		return -EINVAL;
-	}
+	u16 max_size_bw;
 
 	if (is_playback) {
 		chmask = uac2_opts->p_chmask;
@@ -704,14 +686,76 @@ static int set_ep_max_packet_size(const struct f_uac2_opts *uac2_opts,
 		srate = srate * (1000 + uac2_opts->fb_max) / 1000;
 		// updated srate is always bigger, therefore DIV_ROUND_UP always yields +1
 		max_size_bw = num_channels(chmask) * ssize *
-			(DIV_ROUND_UP(srate, factor / (1 << (ep_desc->bInterval - 1))));
+			(DIV_ROUND_UP(srate, factor / (1 << (bint - 1))));
 	} else {
 		// adding 1 frame provision for Win10
 		max_size_bw = num_channels(chmask) * ssize *
-			(DIV_ROUND_UP(srate, factor / (1 << (ep_desc->bInterval - 1))) + 1);
+			(DIV_ROUND_UP(srate, factor / (1 << (bint - 1))) + 1);
 	}
-	ep_desc->wMaxPacketSize = cpu_to_le16(min_t(u16, max_size_bw,
-						    max_size_ep));
+	return max_size_bw;
+}
+
+static int set_ep_max_packet_size_bint(struct device *dev, const struct f_uac2_opts *uac2_opts,
+	struct usb_endpoint_descriptor *ep_desc,
+	enum usb_device_speed speed, bool is_playback)
+{
+	u16 max_size_bw, max_size_ep;
+	u8 bint, opts_bint;
+	char *dir;
+
+	switch (speed) {
+	case USB_SPEED_FULL:
+		max_size_ep = 1023;
+		// fixed
+		bint = ep_desc->bInterval;
+		max_size_bw = get_max_bw_for_bint(uac2_opts, bint, 1000, is_playback);
+		break;
+
+	case USB_SPEED_HIGH:
+	case USB_SPEED_SUPER:
+		max_size_ep = 1024;
+		if (is_playback)
+			opts_bint = uac2_opts->p_hs_bint;
+		else
+			opts_bint = uac2_opts->c_hs_bint;
+
+		if (opts_bint > 0) {
+			/* fixed bint */
+			bint = opts_bint;
+			max_size_bw = get_max_bw_for_bint(uac2_opts, bint, 8000, is_playback);
+		} else {
+			/* checking bInterval from 4 to 1 whether the required bandwidth fits */
+			for (bint = 4; bint > 0; --bint) {
+				max_size_bw = get_max_bw_for_bint(
+					uac2_opts, bint, 8000, is_playback);
+				if (max_size_bw <= max_size_ep)
+					break;
+			}
+		}
+		break;
+
+	default:
+		return -EINVAL;
+	}
+
+	if (is_playback)
+		dir = "Playback";
+	else
+		dir = "Capture";
+
+	if (max_size_bw <= max_size_ep)
+		dev_dbg(dev,
+			"%s: Will use maxpctksize %d and bInterval %d\n",
+			dir, max_size_bw, bint);
+	else {
+		dev_warn(dev,
+			"%s: Req. maxpcktsize %d at bInterval %d > max ISOC %d, may drop data!\n",
+			dir, max_size_bw, bint, max_size_ep);
+		max_size_bw = max_size_ep;
+	}
+
+	ep_desc->wMaxPacketSize = cpu_to_le16(max_size_bw);
+	ep_desc->bInterval = bint;
 
 	return 0;
 }
@@ -965,13 +1009,13 @@ static int afunc_validate_opts(struct g_audio *agdev, struct device *dev)
 			return -EINVAL;
 	}
 
-	if ((opts->p_hs_bint < 1) || (opts->p_hs_bint > 4)) {
-		dev_err(dev, "Error: incorrect playback HS/SS bInterval (1-4)\n");
+	if ((opts->p_hs_bint < 0) || (opts->p_hs_bint > 4)) {
+		dev_err(dev, "Error: incorrect playback HS/SS bInterval (1-4: fixed, 0: auto)\n");
 		return -EINVAL;
 	}
 
-	if ((opts->c_hs_bint < 1) || (opts->c_hs_bint > 4)) {
-		dev_err(dev, "Error: incorrect capture HS/SS bInterval (1-4)\n");
+	if ((opts->c_hs_bint < 0) || (opts->c_hs_bint > 4)) {
+		dev_err(dev, "Error: incorrect capture HS/SS bInterval (1-4: fixed, 0: auto)\n");
 		return -EINVAL;
 	}
 
@@ -1141,43 +1185,43 @@ afunc_bind(struct usb_configuration *cfg, struct usb_function *fn)
 	ss_epout_desc.bInterval = uac2_opts->c_hs_bint;
 
 	/* Calculate wMaxPacketSize according to audio bandwidth */
-	ret = set_ep_max_packet_size(uac2_opts, &fs_epin_desc, USB_SPEED_FULL,
-				     true);
+	ret = set_ep_max_packet_size_bint(dev, uac2_opts, &fs_epin_desc,
+					USB_SPEED_FULL, true);
 	if (ret < 0) {
 		dev_err(dev, "%s:%d Error!\n", __func__, __LINE__);
 		return ret;
 	}
 
-	ret = set_ep_max_packet_size(uac2_opts, &fs_epout_desc, USB_SPEED_FULL,
-				     false);
+	ret = set_ep_max_packet_size_bint(dev, uac2_opts, &fs_epout_desc,
+					USB_SPEED_FULL, false);
 	if (ret < 0) {
 		dev_err(dev, "%s:%d Error!\n", __func__, __LINE__);
 		return ret;
 	}
 
-	ret = set_ep_max_packet_size(uac2_opts, &hs_epin_desc, USB_SPEED_HIGH,
-				     true);
+	ret = set_ep_max_packet_size_bint(dev, uac2_opts, &hs_epin_desc,
+					USB_SPEED_HIGH, true);
 	if (ret < 0) {
 		dev_err(dev, "%s:%d Error!\n", __func__, __LINE__);
 		return ret;
 	}
 
-	ret = set_ep_max_packet_size(uac2_opts, &hs_epout_desc, USB_SPEED_HIGH,
-				     false);
+	ret = set_ep_max_packet_size_bint(dev, uac2_opts, &hs_epout_desc,
+					USB_SPEED_HIGH, false);
 	if (ret < 0) {
 		dev_err(dev, "%s:%d Error!\n", __func__, __LINE__);
 		return ret;
 	}
 
-	ret = set_ep_max_packet_size(uac2_opts, &ss_epin_desc, USB_SPEED_SUPER,
-				     true);
+	ret = set_ep_max_packet_size_bint(dev, uac2_opts, &ss_epin_desc,
+					USB_SPEED_SUPER, true);
 	if (ret < 0) {
 		dev_err(dev, "%s:%d Error!\n", __func__, __LINE__);
 		return ret;
 	}
 
-	ret = set_ep_max_packet_size(uac2_opts, &ss_epout_desc, USB_SPEED_SUPER,
-				     false);
+	ret = set_ep_max_packet_size_bint(dev, uac2_opts, &ss_epout_desc,
+					USB_SPEED_SUPER, false);
 	if (ret < 0) {
 		dev_err(dev, "%s:%d Error!\n", __func__, __LINE__);
 		return ret;
diff --git a/drivers/usb/gadget/function/u_uac2.h b/drivers/usb/gadget/function/u_uac2.h
index 733a0e0945fb..0510c9bad58d 100644
--- a/drivers/usb/gadget/function/u_uac2.h
+++ b/drivers/usb/gadget/function/u_uac2.h
@@ -19,11 +19,11 @@
 #define UAC2_DEF_PCHMASK 0x3
 #define UAC2_DEF_PSRATE 48000
 #define UAC2_DEF_PSSIZE 2
-#define UAC2_DEF_PHSBINT 4
+#define UAC2_DEF_PHSBINT 0
 #define UAC2_DEF_CCHMASK 0x3
 #define UAC2_DEF_CSRATE 64000
 #define UAC2_DEF_CSSIZE 2
-#define UAC2_DEF_CHSBINT 4
+#define UAC2_DEF_CHSBINT 0
 #define UAC2_DEF_CSYNC		USB_ENDPOINT_SYNC_ASYNC
 
 #define UAC2_DEF_MUTE_PRESENT	1