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This change introduces an 'external mode' for GPIO-based FSI masters, allowing the clock and data lines to be driven by an external source. For example, external mode is selected by a user when an external debug device is attached to the FSI pins. To do this, we need to set specific states for the trans, mux and enable GPIOs, and prevent access to clk & data from the FSI core code (by returning EBUSY). External mode is controlled by a sysfs attribute, so add the relevant information to Documentation/ABI/ Signed-off-by: Jeremy Kerr <jk@ozlabs.org> Reviewed-by: Joel Stanley <joel@jms.id.au> Signed-off-by: Joel Stanley <joel@jms.id.au> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
11 lines
433 B
Plaintext
11 lines
433 B
Plaintext
What: /sys/bus/platform/devices/[..]/fsi-master-gpio/external_mode
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Date: Feb 2018
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KernelVersion: 4.17
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Contact: jk@ozlabs.org
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Description:
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Controls access arbitration for GPIO-based FSI master. A
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value of 0 (the default) sets normal mode, where the
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driver performs FSI bus transactions, 1 sets external mode,
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where the FSI bus is driven externally (for example, by
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a debug device).
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