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

[Chen-Yu Tsai]

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.

> 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.

ChenYu