Re: Regression: DVBSky S960 USB tuner doesn't work in 4.10 or newer

[Mauro Carvalho Chehab <mchehab+samsung@kernel.org>]

Em Sat, 28 Apr 2018 08:01:21 +0200
Olli Salonen <olli.salonen@iki.fi> escreveu:

> I did test the patch and while it doesn't seem to introduce any
> negative side effects it does not provide a remedy for the original
> problem that was seen after introducing
> 9d659ae14b545c4296e812c70493bfdc999b5c1c (you probably did not expect
> that either).

Ok, I'll apply it then. Having one less lock makes it cleaner.
> 
> 
> Cheers,
> -olli
> 
> On 27 April 2018 at 18:33, Mauro Carvalho Chehab
> <mchehab+samsung@kernel.org> wrote:
> > Em Fri, 27 Apr 2018 16:25:08 +0200
> > Olli Salonen <olli.salonen@iki.fi> escreveu:
> >
> >> Thanks for the suggestion Antti.
> >>
> >> I've tried to add a delay in various places, but haven't seen any
> >> improvement. However, what I did saw was that if I added an msleep
> >> after the lock:
> >>
> >> static int dvbsky_usb_generic_rw(struct dvb_usb_device *d,
> >>                 u8 *wbuf, u16 wlen, u8 *rbuf, u16 rlen)
> >> {
> >>         int ret;
> >>         struct dvbsky_state *state = d_to_priv(d);
> >>
> >>         mutex_lock(&d->usb_mutex);
> >>         msleep(20);
> >>
> >> The error was seen very within a minute. If I increased the msleep to
> >> 50, it failed within seconds. This doesn't seem to make sense to me.
> >> This is the only function where usb_mutex is used. If the mutex is
> >> held for a longer time, the next attempt to lock the mutex should just
> >> be delayed a bit, no?
> >
> > I don't like the idea of having two mutexes there to protect reading/writing
> > to data one for "generic" r/w ops, and another one just for streaming
> > control, with ends by calling the "generic" mutex.
> >
> > IMHO, I would get rid of one of the mutexes, e. g. something like the
> > patch below (untested).
> >
> > Regards,
> > Mauro
> >
> > media: dvbsky: use just one mutex for serializing device R/W ops
> >
> > Right now, there are two mutexes serializing r/w ops: one "generic"
> > and another one specifically for stream on/off.
> >
> > Clean it a little bit, getting rid of one of the mutexes.
> >
> > Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
> >
> > diff --git a/drivers/media/usb/dvb-usb-v2/dvbsky.c b/drivers/media/usb/dvb-usb-v2/dvbsky.c
> > index 43eb82884555..50553975c39d 100644
> > --- a/drivers/media/usb/dvb-usb-v2/dvbsky.c
> > +++ b/drivers/media/usb/dvb-usb-v2/dvbsky.c
> > @@ -31,7 +31,6 @@ MODULE_PARM_DESC(disable_rc, "Disable inbuilt IR receiver.");
> >  DVB_DEFINE_MOD_OPT_ADAPTER_NR(adapter_nr);
> >
> >  struct dvbsky_state {
> > -       struct mutex stream_mutex;
> >         u8 ibuf[DVBSKY_BUF_LEN];
> >         u8 obuf[DVBSKY_BUF_LEN];
> >         u8 last_lock;
> > @@ -68,18 +67,17 @@ static int dvbsky_usb_generic_rw(struct dvb_usb_device *d,
> >
> >  static int dvbsky_stream_ctrl(struct dvb_usb_device *d, u8 onoff)
> >  {
> > -       struct dvbsky_state *state = d_to_priv(d);
> >         int ret;
> > -       u8 obuf_pre[3] = { 0x37, 0, 0 };
> > -       u8 obuf_post[3] = { 0x36, 3, 0 };
> > +       static u8 obuf_pre[3] = { 0x37, 0, 0 };
> > +       static u8 obuf_post[3] = { 0x36, 3, 0 };
> >
> > -       mutex_lock(&state->stream_mutex);
> > -       ret = dvbsky_usb_generic_rw(d, obuf_pre, 3, NULL, 0);
> > +       mutex_lock(&d->usb_mutex);
> > +       ret = dvb_usbv2_generic_rw_locked(d, obuf_pre, 3, NULL, 0);
> >         if (!ret && onoff) {
> >                 msleep(20);
> > -               ret = dvbsky_usb_generic_rw(d, obuf_post, 3, NULL, 0);
> > +               ret = dvb_usbv2_generic_rw_locked(d, obuf_post, 3, NULL, 0);
> >         }
> > -       mutex_unlock(&state->stream_mutex);
> > +       mutex_unlock(&d->usb_mutex);
> >         return ret;
> >  }
> >
> > @@ -744,8 +742,6 @@ static int dvbsky_init(struct dvb_usb_device *d)
> >         if (ret)
> >                 return ret;
> >         */
> > -       mutex_init(&state->stream_mutex);
> > -
> >         state->last_lock = 0;
> >
> >         return 0;
> >
> >
> >
> > Thanks,
> > Mauro



Thanks,
Mauro