Re: [PATCH 01/19] drm/i915/lnl+/tc: Fix handling of an enabled/disconnected dp-alt sink

[Imre Deak <imre.deak@intel.com>]

On Thu, Aug 07, 2025 at 03:33:04PM +0300, Imre Deak wrote:
> On Thu, Aug 07, 2025 at 03:19:17PM +0300, Jani Nikula wrote:
> > On Thu, 07 Aug 2025, Imre Deak <imre.deak@intel.com> wrote:
> > > On Thu, Aug 07, 2025 at 01:59:21PM +0300, Luca Coelho wrote:
> > >> On Tue, 2025-08-05 at 10:36 +0300, Imre Deak wrote:
> > >> > The TypeC PHY HW readout during driver loading and system resume
> > >> > determines which TypeC mode the PHY is in (legacy/DP-alt/TBT-alt) and
> > >> > whether the PHY is connected, based on the PHY's Owned and Ready flags.
> > >> > For the PHY to be in DP-alt or legacy mode and for the PHY to be in the
> > >> > connected state in these modes, both the Owned (set by the BIOS/driver)
> > >> > and the Ready (set by the HW) flags should be set.
> > >> > 
> > >> > On ICL-MTL the HW kept the PHY's Ready flag set after the driver
> > >> > connected the PHY by acquiring the PHY ownership (by setting the Owned
> > >> > flag), until the driver disconnected the PHY by releasing the PHY
> > >> > ownership (by clearing the Owned flag). On LNL+ this has changed, in
> > >> > that the HW clears the Ready flag as soon as the sink gets disconnected,
> > >> > even if the PHY ownership was acquired already and hence the PHY is
> > >> > being used by the display.
> > >> > 
> > >> > When inheriting the HW state from BIOS for a PHY connected in DP-alt
> > >> > mode on which the sink got disconnected - i.e. in a case where the sink
> > >> > was connected while BIOS/GOP was running and so the sink got enabled
> > >> > connecting the PHY, but the user disconnected the sink by the time the
> > >> > driver loaded - the PHY Owned but not Ready state must be accounted for
> > >> > on LNL+ according to the above. Do that by assuming on LNL+ that the PHY
> > >> > is connected in DP-alt mode whenever the PHY Owned flag is set,
> > >> > regardless of the PHY Ready flag.
> > >> > 
> > >> > This fixes a problem on LNL+, where the PHY TypeC mode / connected state
> > >> > was detected incorrectly for a DP-alt sink, which got connected and then
> > >> > disconnected by the user in the above way.
> > >> > 
> > >> > Cc: stable@vger.kernel.org # v6.8+
> > >> > Reported-by: Charlton Lin <charlton.lin@intel.com>
> > >> > Tested-by: Khaled Almahallawy <khaled.almahallawy@intel.com>
> > >> > Signed-off-by: Imre Deak <imre.deak@intel.com>
> > >> > ---
> > >> >  drivers/gpu/drm/i915/display/intel_tc.c | 16 ++++++++++------
> > >> >  1 file changed, 10 insertions(+), 6 deletions(-)
> > >> > 
> > >> > diff --git a/drivers/gpu/drm/i915/display/intel_tc.c b/drivers/gpu/drm/i915/display/intel_tc.c
> > >> > index 3bc57579fe53e..73a08bd84a70a 100644
> > >> > --- a/drivers/gpu/drm/i915/display/intel_tc.c
> > >> > +++ b/drivers/gpu/drm/i915/display/intel_tc.c
> > >> > @@ -1226,14 +1226,18 @@ static void tc_phy_get_hw_state(struct intel_tc_port *tc)
> > >> >  	tc->phy_ops->get_hw_state(tc);
> > >> >  }
> > >> >  
> > >> > -static bool tc_phy_is_ready_and_owned(struct intel_tc_port *tc,
> > >> > -				      bool phy_is_ready, bool phy_is_owned)
> > >> > +static bool tc_phy_in_legacy_or_dp_alt_mode(struct intel_tc_port *tc,
> > >> > +					    bool phy_is_ready, bool phy_is_owned)
> > >> 
> > >> Personally I don't like the "or" in the function name.  You're
> > >> returning a boolean which is true or false.  The return value is akin
> > >> to answering "Yes/No" to the question "Is it black or white".
> > >
> > > The question the function is meant to answer is "Is the PHY in legacy or
> > > DP-alt mode?". The return value is true (yes) if the PHY is in either
> > > legacy or DP-alt mode, false (no) if the PHY is neither in legacy or
> > > DP-alt mode. There are many other uses of "or" in function names in this
> > > sense, so not sure how else I'd name this one. Simply leaving out "or"
> > > would make it less clear that the legacy and DP-alt modes are two
> > > separate modes.
> > 
> > What's the opposite of "Is the PHY in legacy or DP-alt mode"?
> >
> > Would that lead to a simpler name, with the reversed return value?
> 
> The opposite is either TBT-alt or disconnected mode, so the reversal
> would result in the same function name format.

Would you be ok with

tc_phy_owned_by_display()

?

> 
> > BR,
> > Jani.
> > 
> > 
> > 
> > >
> > >> This is a nitpick, obviously, so I'll leave it up to you.
> > >> 
> > >> Regardless:
> > >> 
> > >> Reviewed-by: Luca Coelho <luciano.coelho@intel.com>
> > >> 
> > >> --
> > >> Cheers,
> > >> Luca.
> > >> 
> > >> >  {
> > >> >  	struct intel_display *display = to_intel_display(tc->dig_port);
> > >> >  
> > >> > -	drm_WARN_ON(display->drm, phy_is_owned && !phy_is_ready);
> > >> > +	if (DISPLAY_VER(display) < 20) {
> > >> > +		drm_WARN_ON(display->drm, phy_is_owned && !phy_is_ready);
> > >> >  
> > >> > -	return phy_is_ready && phy_is_owned;
> > >> > +		return phy_is_ready && phy_is_owned;
> > >> > +	} else {
> > >> > +		return phy_is_owned;
> > >> > +	}
> > >> >  }
> > >> >  
> > >> >  static bool tc_phy_is_connected(struct intel_tc_port *tc,
> > >> > @@ -1244,7 +1248,7 @@ static bool tc_phy_is_connected(struct intel_tc_port *tc,
> > >> >  	bool phy_is_owned = tc_phy_is_owned(tc);
> > >> >  	bool is_connected;
> > >> >  
> > >> > -	if (tc_phy_is_ready_and_owned(tc, phy_is_ready, phy_is_owned))
> > >> > +	if (tc_phy_in_legacy_or_dp_alt_mode(tc, phy_is_ready, phy_is_owned))
> > >> >  		is_connected = port_pll_type == ICL_PORT_DPLL_MG_PHY;
> > >> >  	else
> > >> >  		is_connected = port_pll_type == ICL_PORT_DPLL_DEFAULT;
> > >> > @@ -1352,7 +1356,7 @@ tc_phy_get_current_mode(struct intel_tc_port *tc)
> > >> >  	phy_is_ready = tc_phy_is_ready(tc);
> > >> >  	phy_is_owned = tc_phy_is_owned(tc);
> > >> >  
> > >> > -	if (!tc_phy_is_ready_and_owned(tc, phy_is_ready, phy_is_owned)) {
> > >> > +	if (!tc_phy_in_legacy_or_dp_alt_mode(tc, phy_is_ready, phy_is_owned)) {
> > >> >  		mode = get_tc_mode_in_phy_not_owned_state(tc, live_mode);
> > >> >  	} else {
> > >> >  		drm_WARN_ON(display->drm, live_mode == TC_PORT_TBT_ALT);
> > 
> > -- 
> > Jani Nikula, Intel