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f274baa49b
Currently, USB-audio driver allocates the PCM buffer via vmalloc(), as this serves merely as an intermediate buffer that is copied to each URB transfer buffer. This works well in general on x86, but on some archs this may result in cache coherency issues when mmap is used. OTOH, it works also on such arch unless mmap is used. This patch is a step for mitigating the inconvenience; a new module option "use_vmalloc" is provided so that user can choose to allocate the DMA coherent buffer instead of the existing vmalloc buffer. The drawback is that it'd be the standard dma_alloc_coherent() calls and the system would require contiguous pages on non-x86 archs. Note that it's a global option and not dynamically switchable since the buffer is pre-allocated at the probe time. In theory, it's possible to be switchable, but it'd be trickier and racier. As default use_vmalloc option is set to true, so that the old behavior is kept. For allowing the coherent mmap on ARM or MIPS, pass use_vmalloc=0 option explicitly. Reported-and-tested-by: Daniel Danzberger <daniel@dd-wrt.com> Signed-off-by: Takashi Iwai <tiwai@suse.de>
17 lines
483 B
C
17 lines
483 B
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef __USBAUDIO_PCM_H
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#define __USBAUDIO_PCM_H
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snd_pcm_uframes_t snd_usb_pcm_delay(struct snd_usb_substream *subs,
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unsigned int rate);
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void snd_usb_set_pcm_ops(struct snd_pcm *pcm, int stream);
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int snd_usb_init_pitch(struct snd_usb_audio *chip, int iface,
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struct usb_host_interface *alts,
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struct audioformat *fmt);
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void snd_usb_preallocate_buffer(struct snd_usb_substream *subs);
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#endif /* __USBAUDIO_PCM_H */
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