[PATCH v2 20/21] drm/i915/dp: Read DPRX for all long HPD pulses

[Shankar, Uma]

> -----Original Message-----
> From: Intel-gfx <intel-gfx-bounces at lists.freedesktop.org> On Behalf Of Imre
> Deak
> Sent: Wednesday, February 21, 2024 2:49 AM
> To: intel-gfx at lists.freedesktop.org; dri-devel at lists.freedesktop.org
> Subject: [PATCH v2 20/21] drm/i915/dp: Read DPRX for all long HPD pulses
> 
> The TBT DP tunnel BW request logic in the Thunderbolt Connection Manager
> depends on the GFX driver reading out the sink's DPRX capabilities in response to
> a long HPD pulse. Since in i915 this read-out can be blocked by another
> connector's/encoder's hotplug event handling (which is serialized by
> drm_mode_config::connection_mutex), do a dummy DPRX read-out in the
> encoder's HPD pulse handler (which is not blocked by other encoders).

Looks Good to me.
Reviewed-by: Uma Shankar <uma.shankar at intel.com>

> Signed-off-by: Imre Deak <imre.deak at intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_dp.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c
> b/drivers/gpu/drm/i915/display/intel_dp.c
> index 35ef17439038a..f7f8bd5742ad4 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -6162,6 +6162,7 @@ intel_dp_hpd_pulse(struct intel_digital_port *dig_port,
> bool long_hpd)  {
>  	struct drm_i915_private *i915 = to_i915(dig_port->base.base.dev);
>  	struct intel_dp *intel_dp = &dig_port->dp;
> +	u8 dpcd[DP_RECEIVER_CAP_SIZE];
> 
>  	if (dig_port->base.type == INTEL_OUTPUT_EDP &&
>  	    (long_hpd || !intel_pps_have_panel_power_or_vdd(intel_dp))) { @@ -
> 6184,6 +6185,17 @@ intel_dp_hpd_pulse(struct intel_digital_port *dig_port,
> bool long_hpd)
>  		    dig_port->base.base.name,
>  		    long_hpd ? "long" : "short");
> 
> +	/*
> +	 * TBT DP tunnels require the GFX driver to read out the DPRX caps in
> +	 * response to long HPD pulses. The DP hotplug handler does that,
> +	 * however the hotplug handler may be blocked by another
> +	 * connector's/encoder's hotplug handler. Since the TBT CM may not
> +	 * complete the DP tunnel BW request for the latter connector/encoder
> +	 * waiting for this encoder's DPRX read, perform a dummy read here.
> +	 */
> +	if (long_hpd)
> +		intel_dp_read_dprx_caps(intel_dp, dpcd);
> +
>  	if (long_hpd) {
>  		intel_dp->reset_link_params = true;
>  		return IRQ_NONE;
> --
> 2.39.2