[PATCH] drm/sun4i: tcon: Unconditionally reset the TCON

[Maxime Ripard]

On Fri, Sep 08, 2017 at 02:49:52PM +0800, Chen-Yu Tsai wrote:
> On Fri, Sep 8, 2017 at 2:42 PM, Maxime Ripard
> <maxime.ripard at free-electrons.com> wrote:
> > Hi,
> >
> > On Fri, Sep 08, 2017 at 12:15:45PM +0800, Chen-Yu Tsai wrote:
> >> When binding the TCON, we were checking the reset control status and
> >> asserting reset if it wasn't in reset. The check failed to account for
> >> the reset control API returning error codes if the status callback was
> >> not implemented.
> >>
> >> Since we want the TCON to be reset in all cases, and re-asserting the
> >> reset control does no harm, just assert the reset unconditionally.
> >>
> >> Fixes: 9026e0d122ac ("drm: Add Allwinner A10 Display Engine support")
> >> Signed-off-by: Chen-Yu Tsai <wens at csie.org>
> >> ---
> >>  drivers/gpu/drm/sun4i/sun4i_tcon.c | 3 +--
> >>  1 file changed, 1 insertion(+), 2 deletions(-)
> >>
> >> diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.c b/drivers/gpu/drm/sun4i/sun4i_tcon.c
> >> index d9791292553e..eb32676d5b01 100644
> >> --- a/drivers/gpu/drm/sun4i/sun4i_tcon.c
> >> +++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c
> >> @@ -530,8 +530,7 @@ static int sun4i_tcon_bind(struct device *dev, struct device *master,
> >>       }
> >>
> >>       /* Make sure our TCON is reset */
> >> -     if (!reset_control_status(tcon->lcd_rst))
> >> -             reset_control_assert(tcon->lcd_rst);
> >> +     reset_control_assert(tcon->lcd_rst);
> >
> > That doesn't really reset it if it was already de-asserted. In that
> > case, the TCON will not be reset, unlike what your commit log says.
> 
> Why not? It is now asserting the reset control, regardless of the
> status.

Oh, right, sorry.

> > Maybe you wanted to use reset_control_reset?
> 
> If you prefer it, sure. When I did this patch we didn't support the
> .reset callback, so this is an explicit assert followed by the existing
> deassert.

Still, if we rework that part, I guess that just using reset
unconditonally would make it more obvious.

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
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