Re: [PATCH 2/2] drm/i915/bxt: WA for swapped HPD pins in A stepping

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On 7/15/2015 2:37 PM, Daniel Vetter wrote:
On Wed, Jul 15, 2015 at 01:34:29PM +0530, Jindal, Sonika wrote:


On 7/15/2015 12:05 PM, Jindal, Sonika wrote:


On 7/14/2015 7:52 PM, Imre Deak wrote:
On ti, 2015-07-14 at 11:18 +0530, Sonika Jindal wrote:
As per bspec, on BXT A0/A1, sw needs to activate DDIA HPD logic
and interrupts to check the external panel connection and DDIC HPD
logic for edp panel.

Signed-off-by: Sonika Jindal <sonika.jindal@xxxxxxxxx>
---
   drivers/gpu/drm/i915/intel_dp.c   |   18 ++++++++++++++++--
   drivers/gpu/drm/i915/intel_hdmi.c |    9 ++++++++-
   2 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 7b54b9d..c32f3d3 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -5869,10 +5869,24 @@ intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
   	/* Set up the hotplug pin. */
   	switch (port) {
   	case PORT_A:
-		intel_encoder->hpd_pin = HPD_PORT_A;
+		/*
+		 * On BXT A0/A1, sw needs to activate DDIC HPD logic and
+		 * interrupts to check the eDP panel connection.
+		 */
+		if (IS_BROXTON(dev_priv) && (INTEL_REVID(dev) < BXT_REVID_B0))
+			intel_encoder->hpd_pin = HPD_PORT_C;
+		else
+			intel_encoder->hpd_pin = HPD_PORT_A;
   		break;
   	case PORT_B:
-		intel_encoder->hpd_pin = HPD_PORT_B;
+		/*
+		 * On BXT A0/A1, sw needs to activate DDIA HPD logic and
+		 * interrupts to check the external panel connection.
+		 */
+		if (IS_BROXTON(dev_priv) && (INTEL_REVID(dev) < BXT_REVID_B0))
+			intel_encoder->hpd_pin = HPD_PORT_A;
+		else
+			intel_encoder->hpd_pin = HPD_PORT_B;
   		break;
   	case PORT_C:
   		intel_encoder->hpd_pin = HPD_PORT_C;

This won't work for a couple of reasons: atm i915_digport_work_func()
assumes a fixed pin->port mapping, for example it'll call the HPD
handler for the port A encoder for a short/long pulse event triggered
via the HPD_PORT_A pin, whereas after the above patch you want to select
port B's encoder on BXT A0/1. This could be fixed by setting up
hotplug.irq_port in intel_ddi_init() according to the above change, or
not using irq_port at all, but instead looking up the encoder the same
way i915_hotplug_work_func() does using intel_encoder->hpd_pin.

Yeah that's kinda a bug in digport_work_func, but that part is also a
mess. Simplest would be to rename hotplug.irq_port to irq_pin and change
the assignment for that too.

Hmm, i didnt realize that.
Moving this check to intel_ddi_init, will again make the checks spread
all over which we wanted to avoid since hpd_pin was in place.
But looks like hpd_pin is only for i915_hotplug_work_func.
I feel we can move back to the older approach itself
What do you suggest?

But then we can remove these checks from here, and have it only in
intel_ddi_init, right? So it should look fine.

For HPD_PORT_A, I think we can skip that part as of now.

Please suggest..

I still think that fake-handling hpd A in the low-level irq handler is
massively confusing. And we need to change all the same parts anyway (i.e.
you'd have to change the digport_work_func too with the old approach).
-Daniel

So, for now, I will just correct it in intel_ddi_init and leave the handling of HPD for port A untouched. I will only change the irq_port for external DP (port B). And the other part with hpd_pin to handle hdmi hotplug will remain as is.
Please let me know if you see any issue in this.

Regards,
Sonika

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