From: "Lu, Han" han.lu@intel.com
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.
Signed-off-by: Lu, Han han.lu@intel.com
diff --git a/include/sound/hda_register.h b/include/sound/hda_register.h index 2ae8812..94dc6a9 100644 --- a/include/sound/hda_register.h +++ b/include/sound/hda_register.h @@ -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
diff --git a/sound/pci/hda/hda_controller.c b/sound/pci/hda/hda_controller.c index 22dbfa5..6c2aa4c 100644 --- a/sound/pci/hda/hda_controller.c +++ b/sound/pci/hda/hda_controller.c @@ -27,6 +27,7 @@ #include <linux/module.h> #include <linux/pm_runtime.h> #include <linux/slab.h> +#include <linux/pci.h> #include <sound/core.h> #include <sound/initval.h> #include "hda_controller.h" @@ -34,6 +35,8 @@ #define CREATE_TRACE_POINTS #include "hda_controller_trace.h"
+#define is_broxton(pci) ((pci)->device == 0x5a98) + /* DSP lock helpers */ #define dsp_lock(dev) snd_hdac_dsp_lock(azx_stream(dev)) #define dsp_unlock(dev) snd_hdac_dsp_unlock(azx_stream(dev)) @@ -880,14 +883,35 @@ EXPORT_SYMBOL_GPL(snd_hda_codec_load_dsp_cleanup); #endif /* CONFIG_SND_HDA_DSP_LOADER */
/* + * 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); +} + +/* * reset and start the controller registers */ void azx_init_chip(struct azx *chip, bool full_reset) { + struct pci_dev *pci = chip->pci; + if (snd_hdac_bus_init_chip(azx_bus(chip), full_reset)) { /* correct RINTCNT for CXT */ if (chip->driver_caps & AZX_DCAPS_CTX_WORKAROUND) azx_writew(chip, RINTCNT, 0xc0); + /* reduce dma latency to avoid noise */ + if (is_broxton(pci)) + bxt_reduce_dma_latency(chip); } } EXPORT_SYMBOL_GPL(azx_init_chip);