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List:       alsa-devel
Subject:    Re: [alsa-devel] A bug about cache inconsistency report
From:       Takashi Iwai <tiwai () suse ! de>
Date:       2018-07-31 11:59:20
Message-ID: s5h600vr4yv.wl-tiwai () suse ! de
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On Tue, 31 Jul 2018 12:52:04 +0200,
Hans Hu(SH-RD) wrote:
> 
> Hi All,
> 
> Try send an email.
> 
> Appearance:
> when use non-snoop + ioctl path combination, an issue occurs:
> usage: aplay -D plughw:0,0 44100_S16_LE_2c.wav
> Ubuntu, it performance intermittently noise;
> 
> Root case:
> Function set_pages_array_wc marked the PTE of the original address; Function \
> set_memory_wc marked the PTE both original and after vmaped address. \
> [cid:image002.png@01D428FF.92621520] However, cache or not in transmission process \
> is based on the PTE of the later, and the set_pages_array_wc did't mark it, so a \
> cache inconsistency issue occurs. 
> Related bug:
> SHA1 ID: 9ddf1aeb2134e72275c97a2c6ff2e3eb04f2f27a

OK, so did you confirm that dropping the SG buffer support "fixes" the
noise problem on your system?  The easiest test would be like:

--- a/sound/pci/hda/hda_controller.c
+++ b/sound/pci/hda/hda_controller.c
@@ -770,7 +770,7 @@ int snd_hda_attach_pcm_stream(struct hda_bus *_bus, struct \
hda_codec *codec,  size = CONFIG_SND_HDA_PREALLOC_SIZE * 1024;
 	if (size > MAX_PREALLOC_SIZE)
 		size = MAX_PREALLOC_SIZE;
-	snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_DEV_SG,
+	snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_DEV,
 					      chip->card->dev,
 					      size, MAX_PREALLOC_SIZE);
 	return 0;


thanks,

Takashi
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