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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: Lu, Han <han.lu@intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Lu, Han 2015-12-07 15:59:13 +08:00 committed by Takashi Iwai
parent a74a821624
commit 7c23b7c199
2 changed files with 26 additions and 0 deletions
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3
include/sound/hda_register.h
View File

@ -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

23
sound/pci/hda/hda_intel.c
View File

@ -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 */