diff mbox series

[v2,1/4] drm/i915: Force DPLL calculation for TC ports after readout

Message ID 20220922191236.4194-1-ville.syrjala@linux.intel.com (mailing list archive)
State New, archived
Headers show
Series [v2,1/4] drm/i915: Force DPLL calculation for TC ports after readout | expand

Commit Message

Ville Syrjälä Sept. 22, 2022, 7:12 p.m. UTC 
From: Ville Syrjälä <ville.syrjala@linux.intel.com>

We always allocate two DPLLs (TC and TBT) for TC ports. This
is because we can't know ahead of time wherher we need to put
the PHY into DP-Alt or TBT mode.

However during readout we can obviously only read out the state
of the DPLL that the port is actually using. Thus the state after
readout will not have both DPLLs populated.

We run into problems if during readout the TC port is in DP-Alt
mode, but we then perform a modeset on the port without going
through the full .compute_config() machinery, and during said
modeset the port cannot be switched back into DP-Alt mode and
we need to take the TBT fallback path. Such a modeset can
happen eg. due to cdclk reprogramming.

This wasn't a problem earlier because we did all the DPLL
calculations much later in the modeset. So even if flagged
a modeset very late we'd still have gone through the DPLL
calculations. But now all the DPLL calculations happen much
earlier and so we need to deal with it, or else we'll attempt
a modeset without a DPLL.

To guarantee that we always have both DPLLs fully cal/ulated
for TC ports force a full modeset computation during the
initial commit.

v2: Avoid bitwise operation on bool (Jani)
    Call the return variable 'fastset' to convey its meaning

Reported-by: Lee Shawn C <shawn.c.lee@intel.com>
Fixes: b000abd3b3d2 ("drm/i915: Do .crtc_compute_clock() earlier")
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
 drivers/gpu/drm/i915/display/intel_ddi.c | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

Comments

Jani Nikula Sept. 26, 2022, 5 p.m. UTC | #1 
On Thu, 22 Sep 2022, Ville Syrjala <ville.syrjala@linux.intel.com> wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>
> We always allocate two DPLLs (TC and TBT) for TC ports. This
> is because we can't know ahead of time wherher we need to put
> the PHY into DP-Alt or TBT mode.
>
> However during readout we can obviously only read out the state
> of the DPLL that the port is actually using. Thus the state after
> readout will not have both DPLLs populated.
>
> We run into problems if during readout the TC port is in DP-Alt
> mode, but we then perform a modeset on the port without going
> through the full .compute_config() machinery, and during said
> modeset the port cannot be switched back into DP-Alt mode and
> we need to take the TBT fallback path. Such a modeset can
> happen eg. due to cdclk reprogramming.
>
> This wasn't a problem earlier because we did all the DPLL
> calculations much later in the modeset. So even if flagged
> a modeset very late we'd still have gone through the DPLL
> calculations. But now all the DPLL calculations happen much
> earlier and so we need to deal with it, or else we'll attempt
> a modeset without a DPLL.
>
> To guarantee that we always have both DPLLs fully cal/ulated
> for TC ports force a full modeset computation during the
> initial commit.
>
> v2: Avoid bitwise operation on bool (Jani)
>     Call the return variable 'fastset' to convey its meaning

I think the end result is more readable too.

On the series,

Reviewed-by: Jani Nikula <jani.nikula@intel.com>


>
> Reported-by: Lee Shawn C <shawn.c.lee@intel.com>
> Fixes: b000abd3b3d2 ("drm/i915: Do .crtc_compute_clock() earlier")
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_ddi.c | 18 +++++++++++++++---
>  1 file changed, 15 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c b/drivers/gpu/drm/i915/display/intel_ddi.c
> index 643832d55c28..da8472cdc135 100644
> --- a/drivers/gpu/drm/i915/display/intel_ddi.c
> +++ b/drivers/gpu/drm/i915/display/intel_ddi.c
> @@ -3600,10 +3600,22 @@ static void intel_ddi_sync_state(struct intel_encoder *encoder,
>  static bool intel_ddi_initial_fastset_check(struct intel_encoder *encoder,
>  					    struct intel_crtc_state *crtc_state)
>  {
> -	if (intel_crtc_has_dp_encoder(crtc_state))
> -		return intel_dp_initial_fastset_check(encoder, crtc_state);
> +	struct drm_i915_private *i915 = to_i915(encoder->base.dev);
> +	enum phy phy = intel_port_to_phy(i915, encoder->port);
> +	bool fastset = true;
>  
> -	return true;
> +	if (intel_phy_is_tc(i915, phy)) {
> +		drm_dbg_kms(&i915->drm, "[ENCODER:%d:%s] Forcing full modeset to compute TC port DPLLs\n",
> +			    encoder->base.base.id, encoder->base.name);
> +		crtc_state->uapi.mode_changed = true;
> +		fastset = false;
> +	}
> +
> +	if (intel_crtc_has_dp_encoder(crtc_state) &&
> +	    !intel_dp_initial_fastset_check(encoder, crtc_state))
> +		fastset = false;
> +
> +	return fastset;
>  }
>  
>  static enum intel_output_type
diff mbox series

Patch

diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c b/drivers/gpu/drm/i915/display/intel_ddi.c
index 643832d55c28..da8472cdc135 100644
--- a/drivers/gpu/drm/i915/display/intel_ddi.c
+++ b/drivers/gpu/drm/i915/display/intel_ddi.c
@@ -3600,10 +3600,22 @@  static void intel_ddi_sync_state(struct intel_encoder *encoder,
 static bool intel_ddi_initial_fastset_check(struct intel_encoder *encoder,
 					    struct intel_crtc_state *crtc_state)
 {
-	if (intel_crtc_has_dp_encoder(crtc_state))
-		return intel_dp_initial_fastset_check(encoder, crtc_state);
+	struct drm_i915_private *i915 = to_i915(encoder->base.dev);
+	enum phy phy = intel_port_to_phy(i915, encoder->port);
+	bool fastset = true;
 
-	return true;
+	if (intel_phy_is_tc(i915, phy)) {
+		drm_dbg_kms(&i915->drm, "[ENCODER:%d:%s] Forcing full modeset to compute TC port DPLLs\n",
+			    encoder->base.base.id, encoder->base.name);
+		crtc_state->uapi.mode_changed = true;
+		fastset = false;
+	}
+
+	if (intel_crtc_has_dp_encoder(crtc_state) &&
+	    !intel_dp_initial_fastset_check(encoder, crtc_state))
+		fastset = false;
+
+	return fastset;
 }
 
 static enum intel_output_type