[PATCH v2 17/29] drm: bridge: dw-hdmi: Refactor PHY power handling

[Laurent Pinchart]

Hi Jose,

On Tuesday 20 Dec 2016 12:17:23 Jose Abreu wrote:
> On 20-12-2016 11:45, Russell King - ARM Linux wrote:
> > On Tue, Dec 20, 2016 at 03:33:48AM +0200, Laurent Pinchart wrote:
> >> Instead of spreading version-dependent PHY power handling code around,
> >> group it in two functions to power the PHY on and off and use them
> >> through the driver.
> >> 
> >> Powering off the PHY at the beginning of the setup phase is currently
> >> split in two locations for first and second generation PHYs, group all
> >> the operations in the dw_hdmi_phy_init() function.
> > 
> > This changes the behaviour of the driver.
> > 
> >> +static void dw_hdmi_phy_power_off(struct dw_hdmi *hdmi)
> >> +{
> >> +	if (hdmi->phy->gen == 1) {
> >> +		dw_hdmi_phy_enable_tmds(hdmi, 0);
> >> +		dw_hdmi_phy_enable_powerdown(hdmi, true);
> >> +	} else {
> >> +		dw_hdmi_phy_gen2_txpwron(hdmi, 0);
> >> +		dw_hdmi_phy_gen2_pddq(hdmi, 1);
> >> +	}
> >> +}
> >> @@ -1290,9 +1302,7 @@ static void dw_hdmi_phy_disable(struct dw_hdmi
> >> *hdmi)
> >> 
> >>  	if (!hdmi->phy_enabled)
> >>  	
> >>  		return;
> >> 
> >> -	dw_hdmi_phy_enable_tmds(hdmi, 0);
> >> -	dw_hdmi_phy_enable_powerdown(hdmi, true);
> >> -
> >> +	dw_hdmi_phy_power_off(hdmi);
> > 
> > This makes dw_hdmi_phy_disable() power down a gen2 phy.
> > 
> > The iMX6 has a DW_HDMI_PHY_DWC_HDMI_3D_TX_PHY phy, which you list as a
> > gen2 phy.  I've been carrying this change for a while, which I've had
> > to revert (and finally expunge), as it causes problems on iMX6:
> > 
> > @@ -1112,6 +1112,14 @@ static void dw_hdmi_phy_disable(struct dw_hdmi
> > *hdmi)> 
> >         if (!hdmi->phy_enabled)
> >         
> >                 return;
> > 
> > +       /* Actually set the phy into low power mode */
> > +       dw_hdmi_phy_gen2_txpwron(hdmi, 0);
> > +
> > +       /* FIXME: We should wait for TX_READY to be deasserted */
> > +
> > +       dw_hdmi_phy_gen2_pddq(hdmi, 1);
> > +
> > +       /* This appears to have no effect on iMX6 */
> > 
> >         dw_hdmi_phy_enable_tmds(hdmi, 0);
> >         dw_hdmi_phy_enable_powerdown(hdmi, true);
> > 
> > So, I think your change here will cause problems for iMX6.
> > 
> > From what I remember, it seems that iMX6 has issues with RXSENSE/HPD
> > bouncing when the PHY is powered down.  I can't promise when I'll be
> > able to check for that again.
> 
> Indeed TX_READY must be low before asserting pddq.

The TX_READY signal is documented in the i.MX6 datasheet as being a PHY output 
signal, but there seems to be no HDMI TX register from which its state can be 
read. Do I need to poll the HDMI_PHY_PTRPT_ENBL register through I2C ? How 
long is the PHY expected to take to set TX_READY to 0 ?

> HPD and RXSENSE should work in power down mode by enabling enhpdrxsense
> bit in phy_conf0 BUT to enter power down you must disable TX_PWRON,
> enhpdrxsense and enable PDDQ and PHY_RESET. Only after doing this (and
> consequently entering power down mode) you can enable again enhpdrxsense.

Thanks, I'll give it a try.

-- 
Regards,

Laurent Pinchart