Re: [PATCH 29/32] drm/i915/display: Handle dedicated external ports in intel_encoder_is_tc()

[Gustavo Sousa <gustavo.sousa@intel.com>]

Quoting Jani Nikula (2025-10-15 12:33:31-03:00)
>On Wed, 15 Oct 2025, Gustavo Sousa <gustavo.sousa@intel.com> wrote:
>> Starting with Xe3p_LPD, the VBT has a new field, called in the driver
>> "dedicated_external", which tells that a Type-C capable port is
>> physically connected to a PHY outside of the Type-C subsystem.  When
>> that's the case, the driver must not do the extra Type-C programming for
>> that port.  Update intel_encoder_is_tc() to check for that case.
>>
>> While at it, add a note to intel_phy_is_tc() to remind us that it is
>> about whether the respective port is a Type-C capable port rather than
>> the PHY itself.
>>
>> (Maybe it would be a nice idea to rename intel_phy_is_tc()?)
>>
>> Note that this was handled with a new bool member added to struct
>> intel_digital_port instead of having querying the VBT directly because
>> VBT memory is freed (intel_bios_driver_remove) before encoder cleanup
>> (intel_ddi_encoder_destroy), which would cause an oops to happen when
>> the latter calls intel_encoder_is_tc().  This could be fixed by keeping
>> VBT data around longer, but that's left for a follow-up work, if deemed
>> necessary.
>>
>> Cc: Shekhar Chauhan <shekhar.chauhan@intel.com>
>> Signed-off-by: Gustavo Sousa <gustavo.sousa@intel.com>
>> ---
>>  drivers/gpu/drm/i915/display/intel_ddi.c           |  7 +++++++
>>  drivers/gpu/drm/i915/display/intel_display.c       | 19 ++++++++++++++++++-
>>  drivers/gpu/drm/i915/display/intel_display_types.h |  1 +
>>  3 files changed, 26 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c b/drivers/gpu/drm/i915/display/intel_ddi.c
>> index c09aa759f4d4..6fcbebb81263 100644
>> --- a/drivers/gpu/drm/i915/display/intel_ddi.c
>> +++ b/drivers/gpu/drm/i915/display/intel_ddi.c
>> @@ -5343,6 +5343,13 @@ void intel_ddi_init(struct intel_display *display,
>>                          goto err;
>>          }
>>  
>> +        if (intel_bios_encoder_is_dedicated_external(devdata)) {
>> +                dig_port->dedicated_external = true;
>> +                drm_dbg_kms(display->drm,
>> +                            "Port %c is dedicated external\n",
>> +                            port_name(port));
>> +        }
>
>With the information print added in parse_ddi_port(), the printing here
>becomes redundant.
>
>> +
>>          if (intel_encoder_is_tc(encoder)) {
>>                  bool is_legacy =
>>                          !intel_bios_encoder_supports_typec_usb(devdata) &&
>> diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
>> index 6ac718192e1c..46474199d1ab 100644
>> --- a/drivers/gpu/drm/i915/display/intel_display.c
>> +++ b/drivers/gpu/drm/i915/display/intel_display.c
>> @@ -1778,7 +1778,17 @@ bool intel_phy_is_combo(struct intel_display *display, enum phy phy)
>>                  return false;
>>  }
>>  
>> -/* Prefer intel_encoder_is_tc() */
>> +/*
>> + * This function returns true if the DDI port respective to the PHY enumeration
>> + * is a Type-C capable port.
>> + *
>> + * Depending on the VBT, the port might be configured
>> + * as a "dedicated external" port, meaning that actual physical PHY is outside
>> + * of the Type-C subsystem and, as such, not really a "Type-C PHY".
>> + *
>> + * Prefer intel_encoder_is_tc(), especially if you really need to know if we
>> + * are dealing with Type-C connections.
>> + */
>>  bool intel_phy_is_tc(struct intel_display *display, enum phy phy)
>>  {
>>          /*
>> @@ -1863,6 +1873,13 @@ bool intel_encoder_is_tc(struct intel_encoder *encoder)
>>  {
>>          struct intel_display *display = to_intel_display(encoder);
>>  
>> +        if (intel_encoder_is_dig_port(encoder)) {
>> +                struct intel_digital_port *dig_port = enc_to_dig_port(encoder);
>> +
>> +                if (dig_port->dedicated_external)
>
>Why go through all the trouble of duplicating the "decicated external"
>information in the digital port, when you already have encoder
>available, and can just use intel_bios_encoder_is_dedicated_external()
>right here?

I believe the last paragraph of the commit message explains the why.
Are you suggesting that we handle the lifespan issue right in this
series instead?

Using intel_bios_encoder_is_dedicated_external() my first approach, but
then we were hit with an oops because the VBT data was not available
anymore in the driver unbind path.

--
Gustavo Sousa

>
>> +                        return false;
>> +        }
>> +
>>          return intel_phy_is_tc(display, intel_encoder_to_phy(encoder));
>>  }
>>  
>> diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
>> index 13652e2996a4..b5b9351501b1 100644
>> --- a/drivers/gpu/drm/i915/display/intel_display_types.h
>> +++ b/drivers/gpu/drm/i915/display/intel_display_types.h
>> @@ -1909,6 +1909,7 @@ struct intel_digital_port {
>>          bool lane_reversal;
>>          bool ddi_a_4_lanes;
>>          bool release_cl2_override;
>> +        bool dedicated_external;
>>          u8 max_lanes;
>>          /* Used for DP and ICL+ TypeC/DP and TypeC/HDMI ports. */
>>          enum aux_ch aux_ch;
>
>-- 
>Jani Nikula, Intel