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3641c63926
The Bulk Register Access protocol was left as a TODO topic since 2018. It's time to document this protocol and the design of its Linux support. Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.dev> Signed-off-by: Bard Liao <yung-chuan.liao@linux.intel.com> Reviewed-by: Péter Ujfalusi <peter.ujfalusi@linux.intel.com> Reviewed-by: Liam Girdwood <liam.r.girdwood@intel.com> Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com> Reviewed-by: Bagas Sanjaya <bagasdotme@gmail.com> Tested-by: shumingf@realtek.com Link: https://lore.kernel.org/r/20250227140615.8147-2-yung-chuan.liao@linux.intel.com Signed-off-by: Vinod Koul <vkoul@kernel.org>
67 lines
2.4 KiB
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67 lines
2.4 KiB
ReStructuredText
Cadence IP BRA support
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----------------------
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Format requirements
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~~~~~~~~~~~~~~~~~~~
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The Cadence IP relies on PDI0 for TX and PDI1 for RX. The data needs
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to be formatted with the following conventions:
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(1) all Data is stored in bits 15..0 of the 32-bit PDI FIFOs.
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(2) the start of packet is BIT(31).
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(3) the end of packet is BIT(30).
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(4) A packet ID is stored in bits 19..16. This packet ID is
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determined by software and is typically a rolling counter.
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(5) Padding shall be inserted as needed so that the Header CRC,
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Header response, Footer CRC, Footer response are always in
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Byte0. Padding is inserted by software for writes, and on reads
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software shall discard the padding added by the hardware.
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Example format
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~~~~~~~~~~~~~~
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The following table represents the sequence provided to PDI0 for a
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write command followed by a read command.
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::
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+---+---+--------+---------------+---------------+
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+ 1 | 0 | ID = 0 | WR HDR[1] | WR HDR[0] |
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+ | | | WR HDR[3] | WR HDR[2] |
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+ | | | WR HDR[5] | WR HDR[4] |
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+ | | | pad | WR HDR CRC |
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+ | | | WR Data[1] | WR Data[0] |
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+ | | | WR Data[3] | WR Data[2] |
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+ | | | WR Data[n-2] | WR Data[n-3] |
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+ | | | pad | WR Data[n-1] |
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+ 0 | 1 | | pad | WR Data CRC |
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+---+---+--------+---------------+---------------+
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+ 1 | 0 | ID = 1 | RD HDR[1] | RD HDR[0] |
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+ | | | RD HDR[3] | RD HDR[2] |
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+ | | | RD HDR[5] | RD HDR[4] |
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+ 0 | 1 | | pad | RD HDR CRC |
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+---+---+--------+---------------+---------------+
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The table below represents the data received on PDI1 for the same
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write command followed by a read command.
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::
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+---+---+--------+---------------+---------------+
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+ 1 | 0 | ID = 0 | pad | WR Hdr Rsp |
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+ 0 | 1 | | pad | WR Ftr Rsp |
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+---+---+--------+---------------+---------------+
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+ 1 | 0 | ID = 0 | pad | Rd Hdr Rsp |
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+ | | | RD Data[1] | RD Data[0] |
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+ | | | RD Data[3] | RD Data[2] |
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+ | | | RD HDR[n-2] | RD Data[n-3] |
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+ | | | pad | RD Data[n-1] |
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+ | | | pad | RD Data CRC |
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+ 0 | 1 | | pad | RD Ftr Rsp |
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+---+---+--------+---------------+---------------+
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