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Date:   Tue, 09 Jun 2020 13:45:34 +0200
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From:   Takashi Iwai <tiwai@suse.de>
To:     Christoph Hellwig <hch@lst.de>
Cc:     David Rientjes <rientjes@google.com>,
        "Alex Xu (Hello71)" <alex_y_xu@yahoo.ca>,
        alsa-devel@alsa-project.org, bp@alien8.de, hch@infradead.org,
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        Pavel Machek <pavel@ucw.cz>, perex@perex.cz,
        tglx@linutronix.de, tiwai@suse.com, x86@kernel.org
Subject: Re: next-0519 on thinkpad x60: sound related? window manager crash
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On Tue, 09 Jun 2020 13:40:59 +0200,
Christoph Hellwig wrote:
> 
> On Tue, Jun 09, 2020 at 01:38:46PM +0200, Takashi Iwai wrote:
> > On Tue, 09 Jun 2020 13:31:23 +0200,
> > Christoph Hellwig wrote:
> > > 
> > > On Tue, Jun 09, 2020 at 11:31:20AM +0200, Takashi Iwai wrote:
> > > > > > How would be a proper way to get the virtually mapped SG-buffer pages
> > > > > > with coherent memory?  (Also allowing user-space mmap, too)
> > > > > 
> > > > > dma_mmap_coherent / dma_mmap_attrs for userspace.  We don't really
> > > > > have a good way for kernel space mappings.
> > > > 
> > > > And that's the missing piece right now...  :-<
> > > 
> > > Can you point me to the relevant places (allocation and vmap mostly)
> > > so that I can take a look at how to fix this mess?
> > 
> > Found in sound/core/sgbuf.c.  It's specific to x86.
> 
> So it looks like we could just turn off CONFIG_SND_DMA_SGBUF and
> be done with it?  After all this works on other architectures
> just fine..

Yes, for the sound stuff, something below should make things working.
But it means that we'll lose the SG-buffer allocation and the
allocation of large buffers might fail on some machines.


Takashi

--- a/sound/core/Kconfig
+++ b/sound/core/Kconfig
@@ -192,6 +192,6 @@ config SND_VMASTER
 
 config SND_DMA_SGBUF
 	def_bool y
-	depends on X86
+	depends on X86 && BROKEN
 
 source "sound/core/seq/Kconfig"