ALSA: hda - implement link_power ops for i915 display power control

This patch implements the bus link_power ops to request/release i915 display
power well. It can be used by the display codec which shares this power well
with GPU on Intel platforms.
Signed-off-by: Mengdong Lin <mengdong.lin@intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/pci/hda/hda_controller.c

@@ -775,9 +775,20 @@ static int azx_get_response(struct hdac_bus *bus, unsigned int addr,
 		return azx_rirb_get_response(bus, addr, res);
 }
 
+static int azx_link_power(struct hdac_bus *bus, bool enable)
+{
+	struct azx *chip = bus_to_azx(bus);
+
+	if (chip->ops->link_power)
+		return chip->ops->link_power(chip, enable);
+	else
+		return -EINVAL;
+}
+
 static const struct hdac_bus_ops bus_core_ops = {
 	.command = azx_send_cmd,
 	.get_response = azx_get_response,
+	.link_power = azx_link_power,
 };
 
 #ifdef CONFIG_SND_HDA_DSP_LOADER

sound/pci/hda/hda_controller.h

@@ -89,6 +89,8 @@ struct hda_controller_ops {
 				 struct vm_area_struct *area);
 	/* Check if current position is acceptable */
 	int (*position_check)(struct azx *chip, struct azx_dev *azx_dev);
+	/* enable/disable the link power */
+	int (*link_power)(struct azx *chip, bool enable);
 };
 
 struct azx_pcm {

sound/pci/hda/hda_intel.c

@@ -540,6 +540,14 @@ static int azx_position_check(struct azx *chip, struct azx_dev *azx_dev)
 	return 0;
 }
 
+/* Enable/disable i915 display power for the link */
+static int azx_intel_link_power(struct azx *chip, bool enable)
+{
+	struct hda_intel *hda = container_of(chip, struct hda_intel, chip);
+
+	return hda_display_power(hda, enable);
+}
+
 /*
  * Check whether the current DMA position is acceptable for updating
  * periods.  Returns non-zero if it's OK.
@@ -1786,6 +1794,7 @@ static const struct hda_controller_ops pci_hda_ops = {
 	.substream_free_pages = substream_free_pages,
 	.pcm_mmap_prepare = pcm_mmap_prepare,
 	.position_check = azx_position_check,
+	.link_power = azx_intel_link_power,
 };
 
 static int azx_probe(struct pci_dev *pci,