Re: [linux-sunxi] [PATCH v3 06/16] drm/sun4i: Release exclusive clock lock when disabling TCON

["Jernej Škrabec" <jernej.skrabec@siol.net>]

Hi,

Dne petek, 09. marec 2018 ob 01:44:55 CET je Ond=C5=99ej Jirman napisal(a):
> Hi,
>=20
> I've debugged this further and it seems that the code has incorrect
> assumptions. See docs for mode_set_nofb.
>=20
> https://elixir.bootlin.com/linux/v4.16-rc4/source/include/drm/drm_modeset=
_he
> lper_vtables.h#L209
>

Does this happen with https://github.com/jernejsk/linux-1/tree/h3_hdmi_v3 ?

I also tested running X, but I don't remember having the issue.
=20
> I've added traces to a few functions that call clk_.*exclusive.*()
> functions, and I see this after a few restarts of Xorg server:
>=20
> [    0.783842] *** sun4i_tcon1_mode_set()
> [    0.783886] *** sun4i_tcon_channel_set_status(..., 1, true)
> [    6.881690] *** sun4i_tcon_channel_set_status(..., 1, false)
> [    6.881758] *** sun4i_tcon_channel_set_status(..., 1, true)
> [   52.335085] *** sun4i_tcon_channel_set_status(..., 1, false)
> [   52.335343] *** sun4i_tcon_channel_set_status(..., 1, true)
> [   68.921079] *** sun4i_tcon_channel_set_status(..., 1, false)
> [   68.921337] *** sun4i_tcon_channel_set_status(..., 1, true)
>=20
> mode_set_nofb is called just once, yet sun4i_tcon_channel_set_status(...,=
 1,
> false) is called multiple times, which leads to unbalanced calls to
> clk_set_rate_exclusive and clk_rate_exclusive_put.
>=20
> I don't know how to fix this.

Since there is no function to check if clock is protected, flag can be=20
introduced within TCON which is set when clock rate is protected and unset=
=20
when it is unprotected. That way we could track if clk_rate_exclusive_put()=
=20
needs to be called or not.

Best regards,
Jernej

>=20
> regards,
>   o.
>=20
> On Fri, Mar 09, 2018 at 01:13:14AM +0100, 'Ond=C5=99ej Jirman' via linux-=
sunxi=20
wrote:
> > Hi Jernej,
> >=20
> > On Thu, Mar 08, 2018 at 11:57:40PM +0100, Jernej =C5=A0krabec wrote:
> > > Hi,
> > >=20
> > > Dne =C4=8Detrtek, 08. marec 2018 ob 23:47:17 CET je Ond=C5=99ej Jirma=
n napisal(a):
> > > > Hi,
> > > >=20
> > > > On Thu, Mar 01, 2018 at 10:34:32PM +0100, Jernej Skrabec wrote:
> > > > > Currently exclusive TCON clock lock is never released, which, for
> > > > > example, prevents changing resolution on HDMI.
> > > > >=20
> > > > > In order to fix that, release clock when disabling TCON. TCON is
> > > > > always
> > > > > disabled first before new mode is set.
> > > > >=20
> > > > > Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
> > > > > ---
> > > > >=20
> > > > >  drivers/gpu/drm/sun4i/sun4i_tcon.c | 6 ++++--
> > > > >  1 file changed, 4 insertions(+), 2 deletions(-)
> > > > >=20
> > > > > diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.c
> > > > > b/drivers/gpu/drm/sun4i/sun4i_tcon.c index
> > > > > 1d714c06ec9d..7f6c4125c89f
> > > > > 100644
> > > > > --- a/drivers/gpu/drm/sun4i/sun4i_tcon.c
> > > > > +++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c
> > > > > @@ -102,10 +102,12 @@ static void
> > > > > sun4i_tcon_channel_set_status(struct
> > > > > sun4i_tcon *tcon, int channel,>
> > > > >=20
> > > > >  		return;
> > > > >  =09
> > > > >  	}
> > > > >=20
> > > > > -	if (enabled)
> > > > > +	if (enabled) {
> > > > >=20
> > > > >  		clk_prepare_enable(clk);
> > > > >=20
> > > > > -	else
> > > > > +	} else {
> > > > > +		clk_rate_exclusive_put(clk);
> > > > >=20
> > > > >  		clk_disable_unprepare(clk);
> > > > >=20
> > > > > +	}
> > > > >=20
> > > > >  }
> > > >=20
> > > > At least in the linux-next/master I can't see clk_rate_exclusive_ge=
t=20
call:
> > > It is in drm-misc/drm-misc-fixes:
> > > https://cgit.freedesktop.org/drm/drm-misc/commit/?h=3Ddrm-misc-fixes&=
id=3D79
> > > d103a565d16b1893d990b2ee5e0fe71767759f
> > >=20
> > > My patch is also applied in same branch, so there should be no issues
> > > while
> > > merging all those branches.
> > >=20
> > > linux-next doesn't have either patches currently:
> > > https://git.kernel.org/pub/
> > > scm/linux/kernel/git/next/linux-next.git/log/drivers/gpu/drm/sun4i
> > >=20
> > > This is issue only if you manually apply one patch without the other.
> >=20
> > I have (and had) both patches applied. There's perhaps some code path,
> > where sun4i_tcon_channel_set_status(..., false) is called in unbalanced
> > way with regards to clk_set_rate_exclusive().
> >=20
> > The issue occurs when starting Xorg. But Xorg works fine.
> >=20
> > regards,
> >=20
> >   o.
> >  =20
> > > Best regards,
> > > Jernej
> > >=20
> > > > $ git grep 'exclusive' linux-next/master -- drivers/gpu/drm/sun4i
> > > >=20
> > > > linux-next/master:sun4i_hdmi.h:    * On sun5i the threshold is
> > > > exclusive,
> > > > i.e. does not include, linux-next/master:sun4i_tcon.c:
> > > > clk_rate_exclusive_put(clk); linux-next/master:sun4i_tcon.c:
> > > > clk_set_rate_exclusive(tcon->dclk, mode->crtc_clock * 1000);
> > > > linux-next/master:sun4i_tcon.c:   clk_set_rate_exclusive(tcon->sclk=
1,
> > > > mode->crtc_clock * 1000);
> > > >=20
> > > > and the kernel complains too:
> > > >=20
> > > > [  841.915161] ------------[ cut here ]------------
> > > > [  841.915187] WARNING: CPU: 0 PID: 273 at
> > > > /workspace/megous.com/orangepi-pc/linux-4.16/drivers/clk/clk.c:608
> > > > clk_rate_exclusive_put+0x48/0x4c [  841.915194] CPU: 0 PID: 273 Com=
m:
> > > > Xorg
> > > > Not tainted 4.16.0-rc4-00268-gbac2ecf73ed0 #13 [  841.915196] Hardw=
are
> > > > name: Allwinner sun8i Family
> > > > [  841.915217] [<c0228440>] (unwind_backtrace) from [<c0225b90>]
> > > > (show_stack+0x10/0x14) [  841.915228] [<c0225b90>] (show_stack) from
> > > > [<c0b094bc>] (dump_stack+0x88/0x9c) [  841.915237] [<c0b094bc>]
> > > > (dump_stack) from [<c0240294>] (__warn+0xd4/0xf0) [  841.915244]
> > > > [<c0240294>] (__warn) from [<c0240380>] (warn_slowpath_null+0x40/0x=
48)
> > > > [
> > > > 841.915250] [<c0240380>] (warn_slowpath_null) from [<c0619b6c>]
> > > > (clk_rate_exclusive_put+0x48/0x4c) [  841.915261] [<c0619b6c>]
> > > > (clk_rate_exclusive_put) from [<c0694624>]
> > > > (sun4i_tcon_set_status+0x178/0x2f0) [  841.915269] [<c0694624>]
> > > > (sun4i_tcon_set_status) from [<c06930c0>]
> > > > (sun4i_crtc_atomic_disable+0x7c/0xe4) [  841.915279] [<c06930c0>]
> > > > (sun4i_crtc_atomic_disable) from [<c06637fc>]
> > > > (drm_atomic_helper_commit_modeset_disables+0x390/0x46c) [  841.9152=
88]
> > > > [<c06637fc>] (drm_atomic_helper_commit_modeset_disables) from
> > > > [<c0664df4>]
> > > > (drm_atomic_helper_commit_tail_rpm+0x18/0x64) [  841.915295]
> > > > [<c0664df4>]
> > > > (drm_atomic_helper_commit_tail_rpm) from [<c0664da8>]
> > > > (commit_tail+0x40/0x6c) [  841.915302] [<c0664da8>] (commit_tail) f=
rom
> > > > [<c06652b0>] (drm_atomic_helper_commit+0xbc/0x128) [  841.915311]
> > > > [<c06652b0>] (drm_atomic_helper_commit) from [<c0668d40>]
> > > > (restore_fbdev_mode_atomic+0x100/0x1fc) [  841.915319] [<c0668d40>]
> > > > (restore_fbdev_mode_atomic) from [<c0668f1c>]
> > > > (drm_fb_helper_dpms+0x50/0x130) [  841.915328] [<c0668f1c>]
> > > > (drm_fb_helper_dpms) from [<c0669e9c>] (drm_fb_helper_blank+0x54/0x=
90)
> > > > [
> > > > 841.915337] [<c0669e9c>] (drm_fb_helper_blank) from [<c06088cc>]
> > > > (fb_blank+0x54/0xa8) [  841.915343] [<c06088cc>] (fb_blank) from
> > > > [<c0608c80>] (do_fb_ioctl+0x360/0x62c) [  841.915351] [<c0608c80>]
> > > > (do_fb_ioctl) from [<c0362648>] (do_vfs_ioctl+0x9c/0x774) [=20
> > > > 841.915358]
> > > > [<c0362648>] (do_vfs_ioctl) from [<c0362d54>] (SyS_ioctl+0x34/0x58)=
 [
> > > > 841.915364] [<c0362d54>] (SyS_ioctl) from [<c0201120>]
> > > > (ret_fast_syscall+0x0/0x4c) [  841.915368] Exception stack(0xe5fc5f=
a8
> > > > to
> > > > 0xe5fc5ff0)
> > > > [  841.915373] 5fa0:                   00674f10 00675460 0000000b
> > > > 00004611
> > > > 00000001 00000000 [  841.915379] 5fc0: 00674f10 00675460 00000001
> > > > 00000036
> > > > 00650474 00000000 006504a4 00675df8 [  841.915382] 5fe0: b61a502c
> > > > be8acb2c
> > > > b6192c38 b6b152ec
> > > > [  841.915386] ---[ end trace fa81b956197707f8 ]---
> > > >=20
> > > > It looks like clk_rate_exclusive_put inside
> > > > sun4i_tcon_channel_set_status is called without first calling some
> > > > function that would call
> > > > clk_set_rate_exclusive, leading to unbalanced get/put calls.
> > > >=20
> > > > regards,
> > > >=20
> > > >   o.
> > > >  =20
> > > > >  static void sun4i_tcon_lvds_set_status(struct sun4i_tcon *tcon,
> > > > >=20
> > > > > --
> > > > > 2.16.2
> > > > >=20
> > > > > --
> > > > > You received this message because you are subscribed to the Google
> > > > > Groups
> > > > > "linux-sunxi" group. To unsubscribe from this group and stop
> > > > > receiving
> > > > > emails from it, send an email to
> > > > > linux-sunxi+unsubscribe@googlegroups.com. For more options, visit
> > > > > https://groups.google.com/d/optout.
> > >=20
> > > --
> > > You received this message because you are subscribed to the Google
> > > Groups "linux-sunxi" group. To unsubscribe from this group and stop
> > > receiving emails from it, send an email to
> > > linux-sunxi+unsubscribe@googlegroups.com. For more options, visit
> > > https://groups.google.com/d/optout.
> >=20
> > --
> > You received this message because you are subscribed to the Google Grou=
ps
> > "linux-sunxi" group. To unsubscribe from this group and stop receiving
> > emails from it, send an email to
> > linux-sunxi+unsubscribe@googlegroups.com. For more options, visit
> > https://groups.google.com/d/optout.