On Mon, Dec 10, 2018 at 02:15:11PM -0800, Dhinakaran Pandiyan wrote:
> On Mon, 2018-12-10 at 23:29 +0200, Ville Syrjälä wrote:
> > On Mon, Dec 10, 2018 at 01:07:49PM -0800, Dhinakaran Pandiyan wrote:
> > > The Write_Status_Update_Request I2C transaction requires the MOT
> > > bit to
> > > be set, Change the logical AND to OR to fix what looks like a typo.
> >
> > It's not a type. We're just preserving MOT. What makes you think it
> > should always be set?
> >
> The table defining request commands (2-148) has the MOT bit set for
> Write_Status_Update_Request, doesn't make it look like an option when
> querying the status. Checking the callers again, I see that we could
> get a defer when ending an i2c transaction and that will require a
> Write_Status_Update_Request with MOT unset. Sorry for the noise.
Or a short reply. Admittedly the spec is a bit vague on this topic,
but after trawling it thorougly again I spotted that table 2-151 #9
does have an example of write_status_update with mot==0. So I guess
my original interpretation was in fact correct. Phew :)
>
>
>
>
> > >
> > > Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
> > > Cc: Jani Nikula <jani.nikula@xxxxxxxxx>
> > > Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> > > Fixes: 68ec2a2a2481 ("drm/dp: Use I2C_WRITE_STATUS_UPDATE to drain
> > > partial I2C_WRITE requests")
> > > Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@xxxxxxxxx>
> > > ---
> > > drivers/gpu/drm/drm_dp_helper.c | 2 +-
> > > 1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/gpu/drm/drm_dp_helper.c
> > > b/drivers/gpu/drm/drm_dp_helper.c
> > > index 2d6c491a0542..d98805b517f0 100644
> > > --- a/drivers/gpu/drm/drm_dp_helper.c
> > > +++ b/drivers/gpu/drm/drm_dp_helper.c
> > > @@ -677,7 +677,7 @@ static void
> > > drm_dp_i2c_msg_write_status_update(struct drm_dp_aux_msg *msg)
> > > * rest of the message
> > > */
> > > if ((msg->request & ~DP_AUX_I2C_MOT) == DP_AUX_I2C_WRITE) {
> > > - msg->request &= DP_AUX_I2C_MOT;
> > > + msg->request |= DP_AUX_I2C_MOT;
> > > msg->request |= DP_AUX_I2C_WRITE_STATUS_UPDATE;
> > > }
> > > }
> > > --
> > > 2.17.1
> >
> >
--
Ville Syrjälä
Intel
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