Re: [PATCH] drm/rockchip: vop: power off until vop standby take effect

[Mark yao]

On 2015å02æ02æ 15:53, Daniel Vetter wrote:
> On Mon, Feb 02, 2015 at 10:30:09AM +0800, Mark yao wrote:
> > On 2015å02æ02æ 10:07, Daniel Kurtz wrote:
> > > Hi Mark, Heiko,
> > >
> > > On Sat, Jan 31, 2015 at 4:41 PM, Mark Yao <mark.yao@xxxxxxxxxxxxxx> wrote:
> > > > Vop standby will take effect end of current frame,
> > > > if dsp_hold_valid_irq happen, it means vop standby complete.
> > > >
> > > > we must wait standby complete when we want to disable aclk,
> > > > if not, memory bus maybe dead.
> > > >
> > > > Signed-off-by: Mark Yao <mark.yao@xxxxxxxxxxxxxx>
> > > > ---
> > > >   drivers/gpu/drm/rockchip/rockchip_drm_vop.c |   76 ++++++++++++++++++++++-----
> > > >   1 file changed, 63 insertions(+), 13 deletions(-)
> > > >
> > > > diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
> > > > index fb25836..47ea61f 100644
> > > > --- a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
> > > > +++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
> > > > @@ -89,6 +89,7 @@ struct vop {
> > > >          /* mutex vsync_ work */
> > > >          struct mutex vsync_mutex;
> > > >          bool vsync_work_pending;
> > > > +       struct completion dsp_hold_completion;
> > > >
> > > >          const struct vop_data *data;
> > > >
> > > > @@ -382,6 +383,34 @@ static bool is_alpha_support(uint32_t format)
> > > >          }
> > > >   }
> > > >
> > > > +static void vop_dsp_hold_valid_irq_enable(struct vop *vop)
> > > > +{
> > > > +       unsigned long flags;
> > > > +
> > > > +       BUG_ON(!vop->is_enabled);
> > > Re: Heiko "use a WARN_ON":
> > >
> > > If the VOP clock is off, then the system will just hang when trying to
> > > write the VOP register so in this case, BUG_ON gives a more reliable
> > > crash dump than the hang.
> >    In this way, you are right, if vop clocks is disabled, write vop register
> > will hang system, and the WARN_ON
> if (WARN_ON(cond))
> 	return;
>
> is what we commonly use in i915. Because it's really not any good to use
> BUG_ON in drm drivers, at least if you expect anyone to use fbcon on top
> of it (i.e. anything even remotely resembling a normal distro): Then the
> intial modeset is all done under console_lock, which means that _none_ of
> your BUG_ON will ever get out over serial console.
>
> The problem is fbcon locking, but no fool yet signed up to fix it (it's
> horrible, I looked ...).
> -Daniel
I know this problem, if fbcon locking, and BUG_ON, we can't get any log 
from serial console, Trouble
me many times. So know, if no drm log output, the first thing I do is 
remove the fbcon lock, and then
we can see the crash dump.

But here, I expect to use BUG_ON, because if BUG happen, vop register 
will hang system, and WARN_ON
may be have no chance to output.

Mark

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