[Intel-gfx] [PATCH] [RFC] drm/i915: Handle HPD when it has actually occurred

[Sonika Jindal]

Writing to PCH_PORT_HOTPLUG for each interrupt is not required.
Handle it only if hpd has actually occurred like we handle other
interrupts.

Signed-off-by: Sonika Jindal <sonika.jindal at intel.com>
---
Hi,

I see we don't check for hotplug_trigger before processing the HPD for any of the platform. Is there any reason for this?
For SKL, if I let write to PCH_PORT_HOTPLUG happen for all interrupts, somehow this register gets an invalid value at one point and it zeroes it out.
If I put this check before handling HPD, hotplug behaves fine.
Please let me know if you see any issue with this approach.

Thanks,
Sonika

 drivers/gpu/drm/i915/i915_irq.c |   11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index a6fbe64..2d47372 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -1760,11 +1760,12 @@ static void cpt_irq_handler(struct drm_device *dev, u32 pch_iir)
 	u32 dig_hotplug_reg;
 	u32 pin_mask, long_mask;
 
-	dig_hotplug_reg = I915_READ(PCH_PORT_HOTPLUG);
-	I915_WRITE(PCH_PORT_HOTPLUG, dig_hotplug_reg);
-
-	pch_get_hpd_pins(&pin_mask, &long_mask, hotplug_trigger, dig_hotplug_reg, hpd_cpt);
-	intel_hpd_irq_handler(dev, pin_mask, long_mask);
+	if (hotplug_trigger) {
+		dig_hotplug_reg = I915_READ(PCH_PORT_HOTPLUG);
+		I915_WRITE(PCH_PORT_HOTPLUG, dig_hotplug_reg);
+		pch_get_hpd_pins(&pin_mask, &long_mask, hotplug_trigger, dig_hotplug_reg, hpd_cpt);
+		intel_hpd_irq_handler(dev, pin_mask, long_mask);
+	}
 
 	if (pch_iir & SDE_AUDIO_POWER_MASK_CPT) {
 		int port = ffs((pch_iir & SDE_AUDIO_POWER_MASK_CPT) >>
-- 
1.7.10.4