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

[Takashi Iwai]

At Thu, 26 Jun 2014 15:37:16 +0800,
mengdong.lin at intel.com wrote:
> 
> 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.

Can this be the cause of bko#74861?
   https://bugzilla.kernel.org/show_bug.cgi?id=74861


> 
> 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..90a2750 100644
> --- a/sound/pci/hda/hda_intel.c
> +++ b/sound/pci/hda/hda_intel.c
> @@ -580,6 +580,18 @@ 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)
> +{
> +	chip->bclk_m = azx_readw(chip, EM4);
> +	chip->bclk_n = azx_readw(chip, EM5);
> +}
> +
> +static void haswell_restore_bclk(struct azx *chip)
> +{
> +	azx_writew(chip, EM4, chip->bclk_m);
> +	azx_writew(chip, EM5, chip->bclk_n);
> +}

This is HSW/BDW specific, so we should avoid adding new fields in struct
azx.  Instead, define struct hda_intel in hda_intel.c,

	struct hda_intel {
		struct azx chip;
		
		/* HSW/BDW display HDA controller to restore BCLK from CDCLK */
		unsigned int bclk_m;
		unsigned int bclk_n;
	};

then change azx_create() to allocate struct hda_intel instead of
struct azx.

	struct hda_intel *hda;

	hda = kzalloc(sizeof(*hda), GFP_KERNEL);
	if (!hda) {
		...
	}

	chip = &hda->chip;
	spin_lock_init(&chip->reg_lock);
	mutex_init(&chip->open_mutex);
	chip->card = card;
	...

and access to bclk_m and bclk_n via cast using container_of().

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);
}


> +
>  #if defined(CONFIG_PM_SLEEP) || defined(SUPPORT_VGA_SWITCHEROO)
>  /*
>   * power management
> @@ -606,6 +618,13 @@ 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 +644,10 @@ 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 +691,10 @@ 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 +712,10 @@ 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);
> diff --git a/sound/pci/hda/hda_priv.h b/sound/pci/hda/hda_priv.h
> index 4a7cb01..1469edb 100644
> --- a/sound/pci/hda/hda_priv.h
> +++ b/sound/pci/hda/hda_priv.h
> @@ -96,6 +96,14 @@ enum { SDI0, SDI1, SDI2, SDI3, SDO0, SDO1, SDO2, SDO3 };
>  #define ICH6_REG_SD_BDLPL		0x18
>  #define ICH6_REG_SD_BDLPU		0x1c
>  
> +/* Intel HSW/BDW display HD-A 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

These are definitely not for ICH6.  Define them rather in
hda_intel.c.

I'm going to move more other PCI-controller specific things from
hda_priv.h into hda_intel.c, too.

Also, I guess this deserves for Cc to stable, right?


thanks,

Takashi