Freescale Semiconductor i.MX 6DualLite, Справочное руководство

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• asrc_core_clk: ASRC core clock information, which is used for ASRC register
access.
• asrc_audio_clk: ASRC process clock, which is used for input/output clock source.
26.4.1 Programming Interface (Exported API and IOCTLs)
The ASRC Exported API allows the ALSA driver to use ASRC services.
The ASRC IOCTLs below are used for user space applications:
ASRC_REQ_PAIR:
Apply a pair from ASRC driver. Once a pair is allocated, ASRC core clock is enabled.
ASRC_CONFIG_PAIR:
Configure ASRC pair allocated. User is responsible for providing parameters defined in
struct asrc_config. Items in asrc_config are as follows:
• pair: ASRC pair allocated by the IOCTL(ASRC_REQ_PAIR).
• channel_num: channel number.
• buffer_num: buffer number required by input and output buffer. The input/output
buffers are allocated inside ASRC driver. The user is responsible for remapping it
into user space.
• dma_buffer_size: buffer size for input and output buffers. The buffer size should be
in the unit of page size. Usually, 4 KB is used.
• input_sample_rate: input sampling rate. Input sample rate should be 5.512k, 8k,
11.025k, 16k, 22k, 32k, 44.1k, 48k, 64k, 88.2k 96k, 176.4k, or 192k.
• output_sample_rate: output sampling rate. Output sampling rate should be 32k,
44.1k, 48k, 64k, 88.2k, 96k, 176.4k, or 192k.
• input_word_width: word width of input audio data. The input data word width can be
16 bit or 24 bit.
• output_word_width: word width of output audio data. The output data word width
can be 16 bit or 24 bit.
• inclk: the input clock source can be ESAI RX clock, SSI1 RX clock, SSI2 RX clock,
SPDIF RX clock, MLB_clock, ESAI TX clock, SSI1 TX clock, SSI2 TX clock,
SPDIF TX clock, ASRCLK1 clock, or NONE. If using clock except NONE, the user
should make sure that the clock is available.
• outclk: the output clock source is the same as the input clock source.
ASRC_CONVERT:
Convert the input data into output data according to the parameters set by
ASRC_CONFIG_PAIR. Driver would copy input_buffer_length bytes data from the
input_buffer_vaddr for conversion. After conversion, the driver fills the
Chapter 26 Asynchronous Sample Rate Converter (ASRC) Driver
i.MX 6Solo/6DualLite Linux Reference Manual, Rev. L3.0.35_4.1.0, 09/2013
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