drm/i915: add bxt gmbus support

For BXT gmbus is pulled from PCH to CPU. From implementation point of
view only pin pair configuration will change. The existing
implementation supports all platforms previous to GEN8 and also SKL. But
for BXT pin pair configuration is completely different than SKL or other
previous GEN's. This patch introduces the new pin pair configuration
structure specific to BXT and also ensures every real gmbus port has a
gpio pin.

v3 by Jani: with the platform independent prep work in place, the bxt
enabling reduces to a fairly trivial patch. Credits are due Sunil for
giving me the ideas (with his patches) what the platform independent
parts should look like.

v4: Fix intel_hdmi_init_connector() for bxt. Abstract gmbus_pin access
more. s/GPU/PCH/ in commit message.

v5: Rebase.

Issue: VIZ-3574
Signed-off-by: A.Sunil Kamath <sunil.kamath@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_reg.h

@@ -1794,6 +1794,9 @@ enum skl_disp_power_wells {
 #define   GMBUS_PIN_DPB		5 /* SDVO, HDMIB */
 #define   GMBUS_PIN_DPD		6 /* HDMID */
 #define   GMBUS_PIN_RESERVED	7 /* 7 reserved */
+#define   GMBUS_PIN_1_BXT	1
+#define   GMBUS_PIN_2_BXT	2
+#define   GMBUS_PIN_3_BXT	3
 #define   GMBUS_NUM_PINS	7 /* including 0 */
 #define GMBUS1			0x5104 /* command/status */
 #define   GMBUS_SW_CLR_INT	(1<<31)

drivers/gpu/drm/i915/intel_hdmi.c

@@ -1681,15 +1681,23 @@ void intel_hdmi_init_connector(struct intel_digital_port *intel_dig_port,
 
 	switch (port) {
 	case PORT_B:
-		intel_hdmi->ddc_bus = GMBUS_PIN_DPB;
+		if (IS_BROXTON(dev_priv))
+			intel_hdmi->ddc_bus = GMBUS_PIN_1_BXT;
+		else
+			intel_hdmi->ddc_bus = GMBUS_PIN_DPB;
 		intel_encoder->hpd_pin = HPD_PORT_B;
 		break;
 	case PORT_C:
-		intel_hdmi->ddc_bus = GMBUS_PIN_DPC;
+		if (IS_BROXTON(dev_priv))
+			intel_hdmi->ddc_bus = GMBUS_PIN_2_BXT;
+		else
+			intel_hdmi->ddc_bus = GMBUS_PIN_DPC;
 		intel_encoder->hpd_pin = HPD_PORT_C;
 		break;
 	case PORT_D:
-		if (IS_CHERRYVIEW(dev))
+		if (WARN_ON(IS_BROXTON(dev_priv)))
+			intel_hdmi->ddc_bus = GMBUS_PIN_DISABLED;
+		else if (IS_CHERRYVIEW(dev_priv))
 			intel_hdmi->ddc_bus = GMBUS_PIN_DPD_CHV;
 		else
 			intel_hdmi->ddc_bus = GMBUS_PIN_DPD;

drivers/gpu/drm/i915/intel_i2c.c

@@ -49,10 +49,33 @@ static const struct gmbus_pin gmbus_pins[] = {
 	[GMBUS_PIN_DPD] = { "dpd", GPIOF },
 };
 
+static const struct gmbus_pin gmbus_pins_bxt[] = {
+	[GMBUS_PIN_1_BXT] = { "dpb", PCH_GPIOB },
+	[GMBUS_PIN_2_BXT] = { "dpc", PCH_GPIOC },
+	[GMBUS_PIN_3_BXT] = { "misc", PCH_GPIOD },
+};
+
+/* pin is expected to be valid */
+static const struct gmbus_pin *get_gmbus_pin(struct drm_i915_private *dev_priv,
+					     unsigned int pin)
+{
+	if (IS_BROXTON(dev_priv))
+		return &gmbus_pins_bxt[pin];
+	else
+		return &gmbus_pins[pin];
+}
+
 bool intel_gmbus_is_valid_pin(struct drm_i915_private *dev_priv,
 			      unsigned int pin)
 {
-	return pin < ARRAY_SIZE(gmbus_pins) && gmbus_pins[pin].reg;
+	unsigned int size;
+
+	if (IS_BROXTON(dev_priv))
+		size = ARRAY_SIZE(gmbus_pins_bxt);
+	else
+		size = ARRAY_SIZE(gmbus_pins);
+
+	return pin < size && get_gmbus_pin(dev_priv, pin)->reg;
 }
 
 /* Intel GPIO access functions */
@@ -196,7 +219,8 @@ intel_gpio_setup(struct intel_gmbus *bus, unsigned int pin)
 
 	algo = &bus->bit_algo;
 
-	bus->gpio_reg = dev_priv->gpio_mmio_base + gmbus_pins[pin].reg;
+	bus->gpio_reg = dev_priv->gpio_mmio_base +
+		get_gmbus_pin(dev_priv, pin)->reg;
 
 	bus->adapter.algo_data = algo;
 	algo->setsda = set_data;
@@ -550,7 +574,7 @@ int intel_setup_gmbus(struct drm_device *dev)
 		snprintf(bus->adapter.name,
 			 sizeof(bus->adapter.name),
 			 "i915 gmbus %s",
-			 gmbus_pins[pin].name);
+			 get_gmbus_pin(dev_priv, pin)->name);
 
 		bus->adapter.dev.parent = &dev->pdev->dev;
 		bus->dev_priv = dev_priv;