[alsa-devel] [PATCH v2] ALSA: hda - restore BCLK M/N values when resuming HSW/BDW display controller

[mengdong.lin at intel.com]

From: Mengdong Lin <mengdong.lin at intel.com>

For Intel Haswell/Broadwell display HD-A controller, the 24MHz HD-A link BCLK
is converted from Core Display Clock (CDCLK): BCLK = CDCLK * M / N
And there are two registers EM4 and EM5 to program M, N value respectively.
The EM4/EM5 values will be lost and when the display power well is disabled.

BIOS programs CDCLK selected by OEM and EM4/EM5, but BIOS has no idea about
display power well on/off at runtime. So the M/N can be wrong if non-default
CDCLK is used when the audio controller resumes, which results in an invalid
BCLK and abnormal audio playback rate. So this patch saves and restores valid
M/N values on controller suspend/resume.

And 'struct hda_intel' is defined to contain standard HD-A 'struct azx' and
Intel specific fields, as Takashi suggested.

Signed-off-by: Mengdong Lin <mengdong.lin at intel.com>

diff --git a/sound/pci/hda/hda_intel.c b/sound/pci/hda/hda_intel.c
index bb65a124..ff9cacd 100644
--- a/sound/pci/hda/hda_intel.c
+++ b/sound/pci/hda/hda_intel.c
@@ -288,6 +288,24 @@ static char *driver_short_names[] = {
 	[AZX_DRIVER_GENERIC] = "HD-Audio Generic",
 };
 
+
+/* Intel HSW/BDW display HDA controller Extended Mode registers.
+ * EM4 (M value) and EM5 (N Value) are used to convert CDClk (Core Display
+ * Clock) to 24MHz BCLK: BCLK = CDCLK * M / N
+ * The values will be lost when the display power well is disabled.
+ */
+#define ICH6_REG_EM4			0x100c
+#define ICH6_REG_EM5			0x1010
+
+struct hda_intel {
+	struct azx chip;
+
+	/* HSW/BDW display HDA controller to restore BCLK from CDCLK */
+	unsigned int bclk_m;
+	unsigned int bclk_n;
+};
+
+
 #ifdef CONFIG_X86
 static void __mark_pages_wc(struct azx *chip, struct snd_dma_buffer *dmab, bool on)
 {
@@ -580,6 +598,22 @@ static int param_set_xint(const char *val, const struct kernel_param *kp)
 #define azx_del_card_list(chip) /* NOP */
 #endif /* CONFIG_PM */
 
+static void haswell_save_bclk(struct azx *chip)
+{
+	struct hda_intel *hda = container_of(chip, struct hda_intel, chip);
+
+	hda->bclk_m = azx_readw(chip, EM4);
+	hda->bclk_n = azx_readw(chip, EM5);
+}
+
+static void haswell_restore_bclk(struct azx *chip)
+{
+	struct hda_intel *hda = container_of(chip, struct hda_intel, chip);
+
+	azx_writew(chip, EM4, hda->bclk_m);
+	azx_writew(chip, EM5, hda->bclk_n);
+}
+
 #if defined(CONFIG_PM_SLEEP) || defined(SUPPORT_VGA_SWITCHEROO)
 /*
  * power management
@@ -606,6 +640,13 @@ static int azx_suspend(struct device *dev)
 		free_irq(chip->irq, chip);
 		chip->irq = -1;
 	}
+
+	/* Save BCLK M/N values before they become invalid in D3.
+	 * Will test if display power well can be released now.
+	 */
+	if (chip->driver_caps & AZX_DCAPS_I915_POWERWELL)
+		haswell_save_bclk(chip);
+
 	if (chip->msi)
 		pci_disable_msi(chip->pci);
 	pci_disable_device(pci);
@@ -625,8 +666,10 @@ static int azx_resume(struct device *dev)
 	if (chip->disabled)
 		return 0;
 
-	if (chip->driver_caps & AZX_DCAPS_I915_POWERWELL)
+	if (chip->driver_caps & AZX_DCAPS_I915_POWERWELL) {
 		hda_display_power(true);
+		haswell_restore_bclk(chip);
+	}
 	pci_set_power_state(pci, PCI_D0);
 	pci_restore_state(pci);
 	if (pci_enable_device(pci) < 0) {
@@ -670,8 +713,10 @@ static int azx_runtime_suspend(struct device *dev)
 	azx_stop_chip(chip);
 	azx_enter_link_reset(chip);
 	azx_clear_irq_pending(chip);
-	if (chip->driver_caps & AZX_DCAPS_I915_POWERWELL)
+	if (chip->driver_caps & AZX_DCAPS_I915_POWERWELL) {
+		haswell_save_bclk(chip);
 		hda_display_power(false);
+	}
 	return 0;
 }
 
@@ -689,8 +734,10 @@ static int azx_runtime_resume(struct device *dev)
 	if (!(chip->driver_caps & AZX_DCAPS_PM_RUNTIME))
 		return 0;
 
-	if (chip->driver_caps & AZX_DCAPS_I915_POWERWELL)
+	if (chip->driver_caps & AZX_DCAPS_I915_POWERWELL) {
 		hda_display_power(true);
+		haswell_restore_bclk(chip);
+	}
 
 	/* Read STATESTS before controller reset */
 	status = azx_readw(chip, STATESTS);
@@ -883,6 +930,8 @@ static int register_vga_switcheroo(struct azx *chip)
 static int azx_free(struct azx *chip)
 {
 	struct pci_dev *pci = chip->pci;
+	struct hda_intel *hda = container_of(chip, struct hda_intel, chip);
+
 	int i;
 
 	if ((chip->driver_caps & AZX_DCAPS_PM_RUNTIME)
@@ -930,7 +979,7 @@ static int azx_free(struct azx *chip)
 		hda_display_power(false);
 		hda_i915_exit();
 	}
-	kfree(chip);
+	kfree(hda);
 
 	return 0;
 }
@@ -1174,6 +1223,7 @@ static int azx_create(struct snd_card *card, struct pci_dev *pci,
 	static struct snd_device_ops ops = {
 		.dev_free = azx_dev_free,
 	};
+	struct hda_intel *hda;
 	struct azx *chip;
 	int err;
 
@@ -1183,13 +1233,14 @@ static int azx_create(struct snd_card *card, struct pci_dev *pci,
 	if (err < 0)
 		return err;
 
-	chip = kzalloc(sizeof(*chip), GFP_KERNEL);
-	if (!chip) {
-		dev_err(card->dev, "Cannot allocate chip\n");
+	hda = kzalloc(sizeof(*hda), GFP_KERNEL);
+	if (!hda) {
+		dev_err(card->dev, "Cannot allocate hda\n");
 		pci_disable_device(pci);
 		return -ENOMEM;
 	}
 
+	chip = &hda->chip;
 	spin_lock_init(&chip->reg_lock);
 	mutex_init(&chip->open_mutex);
 	chip->card = card;
-- 
1.8.1.2