SoundWire: add read-write command interface in debugfs #4676
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The existing code sets the maximum address at 0x80000000, which is not completely accurate. The last 2 Gbytes are indeed reserved, but so are the 896 Mbytes just before. The maximum address which can be used with paging or BRA is 0x47FFFFFF per Table 131 of the SoundWire 1.2.1 specification. Signed-off-by: Pierre-Louis Bossart <[email protected]>
We have an existing debugfs files to read standard registers (DP0/SCP/DPn). This patch provides a more generic interface to read/write contiguous registers in a peripheral device. In follow-up patches, this interface will be extended to use BRA transfers. Example for a read command: cd /sys/kernel/debug/soundwire/master-0-0/sdw\:0\:025d\:0711\:01/ echo 1 > command echo 6 > num_bytes echo 0x50 > start_address echo 1 > go cat read_buffer address 0x50 val 0x30 address 0x51 val 0x02 address 0x52 val 0x5d address 0x53 val 0x07 address 0x54 val 0x11 address 0x55 val 0x01 FIXME: what should be the interface for writes? I am leaning on the use of a binary firmware file, because that's typically what people want to do. Signed-off-by: Pierre-Louis Bossart <[email protected]>
Example with a 2-byte firmware file written in DP0 address 0x22 od -x /lib/firmware/test_firmware 0000000 0a37 0000002 cd /sys/kernel/debug/soundwire/master-0-0/sdw\:0\:025d\:0711\:01/ echo 0 > command echo 2 > num_bytes echo 0x22 > start_address echo "test_firmware" > firmware_file echo 1 > go cd /sys/kernel/debug/soundwire/master-0-0/sdw\:0\:025d\:0711\:01/ echo 1 > command echo 2 > num_bytes echo 0x22 > start_address echo 1 > go cat read_buffer address 0x22 val 0x37 address 0x23 val 0x0a Signed-off-by: Pierre-Louis Bossart <[email protected]>
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This is a WIP PR to check how we can provide peripheral drivers with the capability to read/write contiguous registers from debugfs. Once this is up and running, we can use this interface to test BRA capabilities.
@bardliao @ujfalusi @shumingfan @jack-cy-yu @oder-chiou @charleskeepax @rfvirgil comments welcome.