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Commit 7c23b7c1 authored by Lu, Han's avatar Lu, Han Committed by Takashi Iwai
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ALSA: hda - Fix playback noise with 24/32 bit sample size on BXT 



In BXT-P A0, HD-Audio DMA requests is later than expected,
and makes an audio stream sensitive to system latencies when
24/32 bits are playing.
Adjusting threshold of DMA fifo to force the DMA request
sooner to improve latency tolerance at the expense of power.

v2: move Intel specific code to hda_intel.c

Signed-off-by: default avatarLu, Han <han.lu@intel.com>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent a74a8216

include/sound/hda_register.h

+3 −0
Original line number Diff line number Diff line
@@ -93,6 +93,9 @@ enum { SDI0, SDI1, SDI2, SDI3, SDO0, SDO1, SDO2, SDO3 }; 
#define AZX_REG_HSW_EM4			0x100c

#define AZX_REG_HSW_EM5			0x1010



/* Skylake/Broxton display HD-A controller Extended Mode registers */

#define AZX_REG_SKL_EM4L		0x1040



/* PCI space */

#define AZX_PCIREG_TCSEL		0x44

sound/pci/hda/hda_intel.c

+23 −0
Original line number Diff line number Diff line
@@ -355,6 +355,8 @@ enum { 
					((pci)->device == 0x0d0c) || \

					((pci)->device == 0x160c))



#define IS_BROXTON(pci)	((pci)->device == 0x5a98)



static char *driver_short_names[] = {

	[AZX_DRIVER_ICH] = "HDA Intel",

	[AZX_DRIVER_PCH] = "HDA Intel PCH",
@@ -506,15 +508,36 @@ static void azx_init_pci(struct azx *chip) 
        }

}



/*

 * In BXT-P A0, HD-Audio DMA requests is later than expected,

 * and makes an audio stream sensitive to system latencies when

 * 24/32 bits are playing.

 * Adjusting threshold of DMA fifo to force the DMA request

 * sooner to improve latency tolerance at the expense of power.

 */

static void bxt_reduce_dma_latency(struct azx *chip)

{

	u32 val;



	val = azx_readl(chip, SKL_EM4L);

	val &= (0x3 << 20);

	azx_writel(chip, SKL_EM4L, val);

}



static void hda_intel_init_chip(struct azx *chip, bool full_reset)

{

	struct hdac_bus *bus = azx_bus(chip);

	struct pci_dev *pci = chip->pci;



	if (chip->driver_caps & AZX_DCAPS_I915_POWERWELL)

		snd_hdac_set_codec_wakeup(bus, true);

	azx_init_chip(chip, full_reset);

	if (chip->driver_caps & AZX_DCAPS_I915_POWERWELL)

		snd_hdac_set_codec_wakeup(bus, false);



	/* reduce dma latency to avoid noise */

	if (IS_BROXTON(pci))

		bxt_reduce_dma_latency(chip);

}



/* calculate runtime delay from LPIB */