[Intel-gfx] [PATCH 3/5] drm/dp: Implement I2C_M_STOP for i2c-over-aux

[Daniel Vetter]

On Mon, Dec 10, 2018 at 06:47:00PM -0800, Dhinakaran Pandiyan wrote:
> On Fri, 2018-09-28 at 21:04 +0300, Ville Syrjala wrote:
> > From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > 
> > Consult the I2C_M_STOP flag to determine whether to set the MOT bit
> > or
> > not. Makes it possible to send multiple messages in one go with
> > stop+start generated between the messages (as opposed nothing or
> > repstart depending on whether thr address/rw changed).
> > 
> > Not sure anyone has actual use for this but figured I'd handle it
> > since I started to look at that flag for MST remote i2c xfers.
> > 
> Don't see the I2C_M_STOP flag anywhere in drm_edid.c, but the change
> introduced here does make sense.

Iirc it's the i2c core library which takes an entire transaction, splits
it up, and sets the stop flag only on the very last one. Or something like
that.
-Daniel

> 
> Reviewed-by: Dhinakaran Pandiyan <dhinakaran.pandiyan at intel.com>
> > Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > ---
> >  drivers/gpu/drm/drm_dp_helper.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_dp_helper.c
> > b/drivers/gpu/drm/drm_dp_helper.c
> > index 37c01b6076ec..e85cea299d2a 100644
> > --- a/drivers/gpu/drm/drm_dp_helper.c
> > +++ b/drivers/gpu/drm/drm_dp_helper.c
> > @@ -884,7 +884,8 @@ static void drm_dp_i2c_msg_set_request(struct
> > drm_dp_aux_msg *msg,
> >  {
> >  	msg->request = (i2c_msg->flags & I2C_M_RD) ?
> >  		DP_AUX_I2C_READ : DP_AUX_I2C_WRITE;
> > -	msg->request |= DP_AUX_I2C_MOT;
> > +	if (!(i2c_msg->flags & I2C_M_STOP))
> > +		msg->request |= DP_AUX_I2C_MOT;
> >  }
> >  
> >  /*
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch