[PATCH v2 1/3] Revert "usb: gadget: u_audio: add real feedback implementation"

From: Ferry Toth
Date: Thu Aug 26 2021 - 15:14:32 EST

This reverts commit e89bb4288378b85c82212b60dc98ecda6b3d3a70.

The commit is part of a series with commit
24f779dac8f3efb9629adc0e486914d93dc45517 causing a BUG on dwc3
hardware, at least on Intel Merrifield platform when configured
through configfs:
BUG: kernel NULL pointer dereference, address: 0000000000000008
...
RIP: 0010:dwc3_gadget_del_and_unmap_request+0x19/0xe0
...
Call Trace:
dwc3_remove_requests.constprop.0+0x12f/0x170
__dwc3_gadget_ep_disable+0x7a/0x160
dwc3_gadget_ep_disable+0x3d/0xd0
usb_ep_disable+0x1c/0x70
u_audio_stop_capture+0x79/0x120 [u_audio]
afunc_set_alt+0x73/0x80 [usb_f_uac2]
composite_setup+0x224/0x1b90 [libcomposite]

Pavel's suggestion to add
`echo "adaptive" > functions/uac2.usb0/c_sync` to the configfs script
resolves the issue.
Thinh suggests "the crash is probably because of f_uac2 prematurely
freeing feedback request before its completion. usb_ep_dequeue() is
asynchronous. dwc2() may treat it as a synchronous call so you didn't
get a crash."

Revert as this is a regression and the kernel shouldn't crash depending
on configuration parameters.

Signed-off-by: Ferry Toth <ftoth@xxxxxxxxxxxxxx>
---
.../ABI/testing/configfs-usb-gadget-uac2 | 1 -
Documentation/usb/gadget-testing.rst | 1 -
drivers/usb/gadget/function/f_uac2.c | 9 +-
drivers/usb/gadget/function/u_audio.c | 124 ++----------------
drivers/usb/gadget/function/u_audio.h | 9 --
drivers/usb/gadget/function/u_uac2.h | 2 -
6 files changed, 10 insertions(+), 136 deletions(-)

diff --git a/Documentation/ABI/testing/configfs-usb-gadget-uac2 b/Documentation/ABI/testing/configfs-usb-gadget-uac2
index 26fb8e9b4e61..e7e59d7fb12f 100644
--- a/Documentation/ABI/testing/configfs-usb-gadget-uac2
+++ b/Documentation/ABI/testing/configfs-usb-gadget-uac2
@@ -9,7 +9,6 @@ Description:
c_srate capture sampling rate
c_ssize capture sample size (bytes)
c_sync capture synchronization type (async/adaptive)
- fb_max maximum extra bandwidth in async mode
p_chmask playback channel mask
p_srate playback sampling rate
p_ssize playback sample size (bytes)
diff --git a/Documentation/usb/gadget-testing.rst b/Documentation/usb/gadget-testing.rst
index 9d6276f82774..f5a12667bd41 100644
--- a/Documentation/usb/gadget-testing.rst
+++ b/Documentation/usb/gadget-testing.rst
@@ -729,7 +729,6 @@ The uac2 function provides these attributes in its function directory:
c_srate capture sampling rate
c_ssize capture sample size (bytes)
c_sync capture synchronization type (async/adaptive)
- fb_max maximum extra bandwidth in async mode
p_chmask playback channel mask
p_srate playback sampling rate
p_ssize playback sample size (bytes)
diff --git a/drivers/usb/gadget/function/f_uac2.c b/drivers/usb/gadget/function/f_uac2.c
index ae29ff2b2b68..321e6c05ba93 100644
--- a/drivers/usb/gadget/function/f_uac2.c
+++ b/drivers/usb/gadget/function/f_uac2.c
@@ -584,11 +584,8 @@ static int set_ep_max_packet_size(const struct f_uac2_opts *uac2_opts,
ssize = uac2_opts->c_ssize;
}

- if (!is_playback && (uac2_opts->c_sync == USB_ENDPOINT_SYNC_ASYNC))
- srate = srate * (1000 + uac2_opts->fb_max) / 1000;
-
max_size_bw = num_channels(chmask) * ssize *
- DIV_ROUND_UP(srate, factor / (1 << (ep_desc->bInterval - 1)));
+ ((srate / (factor / (1 << (ep_desc->bInterval - 1)))) + 1);
ep_desc->wMaxPacketSize = cpu_to_le16(min_t(u16, max_size_bw,
max_size_ep));

@@ -960,7 +957,6 @@ afunc_bind(struct usb_configuration *cfg, struct usb_function *fn)
agdev->params.c_srate = uac2_opts->c_srate;
agdev->params.c_ssize = uac2_opts->c_ssize;
agdev->params.req_number = uac2_opts->req_number;
- agdev->params.fb_max = uac2_opts->fb_max;
ret = g_audio_setup(agdev, "UAC2 PCM", "UAC2_Gadget");
if (ret)
goto err_free_descs;
@@ -1333,7 +1329,6 @@ UAC2_ATTRIBUTE(c_srate);
UAC2_ATTRIBUTE_SYNC(c_sync);
UAC2_ATTRIBUTE(c_ssize);
UAC2_ATTRIBUTE(req_number);
-UAC2_ATTRIBUTE(fb_max);

static struct configfs_attribute *f_uac2_attrs[] = {
&f_uac2_opts_attr_p_chmask,
@@ -1344,7 +1339,6 @@ static struct configfs_attribute *f_uac2_attrs[] = {
&f_uac2_opts_attr_c_ssize,
&f_uac2_opts_attr_c_sync,
&f_uac2_opts_attr_req_number,
- &f_uac2_opts_attr_fb_max,
NULL,
};

@@ -1384,7 +1378,6 @@ static struct usb_function_instance *afunc_alloc_inst(void)
opts->c_ssize = UAC2_DEF_CSSIZE;
opts->c_sync = UAC2_DEF_CSYNC;
opts->req_number = UAC2_DEF_REQ_NUM;
- opts->fb_max = UAC2_DEF_FB_MAX;
return &opts->func_inst;
}

diff --git a/drivers/usb/gadget/function/u_audio.c b/drivers/usb/gadget/function/u_audio.c
index 018dd0978995..f637ebec80b0 100644
--- a/drivers/usb/gadget/function/u_audio.c
+++ b/drivers/usb/gadget/function/u_audio.c
@@ -16,7 +16,6 @@
#include <sound/core.h>
#include <sound/pcm.h>
#include <sound/pcm_params.h>
-#include <sound/control.h>

#include "u_audio.h"

@@ -36,12 +35,12 @@ struct uac_rtd_params {

void *rbuf;

- unsigned int pitch; /* Stream pitch ratio to 1000000 */
unsigned int max_psize; /* MaxPacketSize of endpoint */

struct usb_request **reqs;

struct usb_request *req_fback; /* Feedback endpoint request */
+ unsigned int ffback; /* Real frequency reported by feedback endpoint */
bool fb_ep_enabled; /* if the ep is enabled */
};

@@ -76,29 +75,18 @@ static const struct snd_pcm_hardware uac_pcm_hardware = {
};

static void u_audio_set_fback_frequency(enum usb_device_speed speed,
- unsigned long long freq,
- unsigned int pitch,
- void *buf)
+ unsigned int freq, void *buf)
{
u32 ff = 0;

- /*
- * Because the pitch base is 1000000, the final divider here
- * will be 1000 * 1000000 = 1953125 << 9
- *
- * Instead of dealing with big numbers lets fold this 9 left shift
- */
-
if (speed == USB_SPEED_FULL) {
/*
* Full-speed feedback endpoints report frequency
- * in samples/frame
+ * in samples/microframe
* Format is encoded in Q10.10 left-justified in the 24 bits,
* so that it has a Q10.14 format.
- *
- * ff = (freq << 14) / 1000
*/
- freq <<= 5;
+ ff = DIV_ROUND_UP((freq << 14), 1000);
} else {
/*
* High-speed feedback endpoints report frequency
@@ -106,14 +94,9 @@ static void u_audio_set_fback_frequency(enum usb_device_speed speed,
* Format is encoded in Q12.13 fitted into four bytes so that
* the binary point is located between the second and the third
* byte fromat (that is Q16.16)
- *
- * ff = (freq << 16) / 8000
*/
- freq <<= 4;
+ ff = DIV_ROUND_UP((freq << 13), 1000);
}
-
- ff = DIV_ROUND_CLOSEST_ULL((freq * pitch), 1953125);
-
*(__le32 *)buf = cpu_to_le32(ff);
}

@@ -226,8 +209,8 @@ static void u_audio_iso_fback_complete(struct usb_ep *ep,
struct uac_rtd_params *prm = req->context;
struct snd_uac_chip *uac = prm->uac;
struct g_audio *audio_dev = uac->audio_dev;
- struct uac_params *params = &audio_dev->params;
int status = req->status;
+ unsigned long flags;

/* i/f shutting down */
if (!prm->fb_ep_enabled || req->status == -ESHUTDOWN)
@@ -242,8 +225,7 @@ static void u_audio_iso_fback_complete(struct usb_ep *ep,
__func__, status, req->actual, req->length);

u_audio_set_fback_frequency(audio_dev->gadget->speed,
- params->c_srate, prm->pitch,
- req->buf);
+ prm->ffback, req->buf);

if (usb_ep_queue(ep, req, GFP_ATOMIC))
dev_err(uac->card->dev, "%d Error!\n", __LINE__);
@@ -498,10 +480,9 @@ int u_audio_start_capture(struct g_audio *audio_dev)
* Always start with original frequency since its deviation can't
* be meauserd at start of playback
*/
- prm->pitch = 1000000;
+ prm->ffback = params->c_srate;
u_audio_set_fback_frequency(audio_dev->gadget->speed,
- params->c_srate, prm->pitch,
- req_fback->buf);
+ prm->ffback, req_fback->buf);

if (usb_ep_queue(ep_fback, req_fback, GFP_ATOMIC))
dev_err(dev, "%s:%d Error!\n", __func__, __LINE__);
@@ -597,82 +578,12 @@ void u_audio_stop_playback(struct g_audio *audio_dev)
}
EXPORT_SYMBOL_GPL(u_audio_stop_playback);

-static int u_audio_pitch_info(struct snd_kcontrol *kcontrol,
- struct snd_ctl_elem_info *uinfo)
-{
- struct uac_rtd_params *prm = snd_kcontrol_chip(kcontrol);
- struct snd_uac_chip *uac = prm->uac;
- struct g_audio *audio_dev = uac->audio_dev;
- struct uac_params *params = &audio_dev->params;
- unsigned int pitch_min, pitch_max;
-
- pitch_min = (1000 - FBACK_SLOW_MAX) * 1000;
- pitch_max = (1000 + params->fb_max) * 1000;
-
- uinfo->type = SNDRV_CTL_ELEM_TYPE_INTEGER;
- uinfo->count = 1;
- uinfo->value.integer.min = pitch_min;
- uinfo->value.integer.max = pitch_max;
- uinfo->value.integer.step = 1;
- return 0;
-}
-
-static int u_audio_pitch_get(struct snd_kcontrol *kcontrol,
- struct snd_ctl_elem_value *ucontrol)
-{
- struct uac_rtd_params *prm = snd_kcontrol_chip(kcontrol);
-
- ucontrol->value.integer.value[0] = prm->pitch;
-
- return 0;
-}
-
-static int u_audio_pitch_put(struct snd_kcontrol *kcontrol,
- struct snd_ctl_elem_value *ucontrol)
-{
- struct uac_rtd_params *prm = snd_kcontrol_chip(kcontrol);
- struct snd_uac_chip *uac = prm->uac;
- struct g_audio *audio_dev = uac->audio_dev;
- struct uac_params *params = &audio_dev->params;
- unsigned int val;
- unsigned int pitch_min, pitch_max;
- int change = 0;
-
- pitch_min = (1000 - FBACK_SLOW_MAX) * 1000;
- pitch_max = (1000 + params->fb_max) * 1000;
-
- val = ucontrol->value.integer.value[0];
-
- if (val < pitch_min)
- val = pitch_min;
- if (val > pitch_max)
- val = pitch_max;
-
- if (prm->pitch != val) {
- prm->pitch = val;
- change = 1;
- }
-
- return change;
-}
-
-static const struct snd_kcontrol_new u_audio_controls[] = {
-{
- .iface = SNDRV_CTL_ELEM_IFACE_PCM,
- .name = "Capture Pitch 1000000",
- .info = u_audio_pitch_info,
- .get = u_audio_pitch_get,
- .put = u_audio_pitch_put,
-},
-};
-
int g_audio_setup(struct g_audio *g_audio, const char *pcm_name,
const char *card_name)
{
struct snd_uac_chip *uac;
struct snd_card *card;
struct snd_pcm *pcm;
- struct snd_kcontrol *kctl;
struct uac_params *params;
int p_chmask, c_chmask;
int err;
@@ -760,23 +671,6 @@ int g_audio_setup(struct g_audio *g_audio, const char *pcm_name,
snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_PLAYBACK, &uac_pcm_ops);
snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_CAPTURE, &uac_pcm_ops);

- if (c_chmask && g_audio->in_ep_fback) {
- strscpy(card->mixername, card_name, sizeof(card->driver));
-
- kctl = snd_ctl_new1(&u_audio_controls[0], &uac->c_prm);
- if (!kctl) {
- err = -ENOMEM;
- goto snd_fail;
- }
-
- kctl->id.device = pcm->device;
- kctl->id.subdevice = 0;
-
- err = snd_ctl_add(card, kctl);
- if (err < 0)
- goto snd_fail;
- }
-
strscpy(card->driver, card_name, sizeof(card->driver));
strscpy(card->shortname, card_name, sizeof(card->shortname));
sprintf(card->longname, "%s %i", card_name, card->dev->id);
diff --git a/drivers/usb/gadget/function/u_audio.h b/drivers/usb/gadget/function/u_audio.h
index a218cdf771fe..53e6baf55cbf 100644
--- a/drivers/usb/gadget/function/u_audio.h
+++ b/drivers/usb/gadget/function/u_audio.h
@@ -11,14 +11,6 @@

#include <linux/usb/composite.h>

-/*
- * Same maximum frequency deviation on the slower side as in
- * sound/usb/endpoint.c. Value is expressed in per-mil deviation.
- * The maximum deviation on the faster side will be provided as
- * parameter, as it impacts the endpoint required bandwidth.
- */
-#define FBACK_SLOW_MAX 250
-
struct uac_params {
/* playback */
int p_chmask; /* channel mask */
@@ -31,7 +23,6 @@ struct uac_params {
int c_ssize; /* sample size */

int req_number; /* number of preallocated requests */
- int fb_max; /* upper frequency drift feedback limit per-mil */
};

struct g_audio {
diff --git a/drivers/usb/gadget/function/u_uac2.h b/drivers/usb/gadget/function/u_uac2.h
index 179d3ef6a195..13589c3c805c 100644
--- a/drivers/usb/gadget/function/u_uac2.h
+++ b/drivers/usb/gadget/function/u_uac2.h
@@ -23,7 +23,6 @@
#define UAC2_DEF_CSSIZE 2
#define UAC2_DEF_CSYNC USB_ENDPOINT_SYNC_ASYNC
#define UAC2_DEF_REQ_NUM 2
-#define UAC2_DEF_FB_MAX 5

struct f_uac2_opts {
struct usb_function_instance func_inst;
@@ -35,7 +34,6 @@ struct f_uac2_opts {
int c_ssize;
int c_sync;
int req_number;
- int fb_max;
bool bound;

struct mutex lock;
--
2.30.2