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48 lines
1.5 KiB
Text
48 lines
1.5 KiB
Text
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==================================
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TWserial device subsystem analysis
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==================================
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Tomas Hlavacek<tmshlvck@gmail.com>
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2012-03-21
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I) Overview
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-----------
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U-Boot currently implements one common API for TWSerial devices. The interface
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is defined in include/tws.h and comprises of functions:
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int tws_read(uchar *buffer, int len);
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int tws_write(uchar *buffer, int len);
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The functions are implemented by a proper device driver in drivers/twserial
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directory and the driver to be compiled in is selected in a Makefile. There is
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only one driver present now.
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The driver depends on ad-hoc code in board specific data, namely functions:
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void tws_ce(unsigned bit);
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void tws_wr(unsigned bit);
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void tws_clk(unsigned bit);
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void tws_data(unsigned bit);
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unsigned tws_data_read(void);
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void tws_data_config_output(unsigned output);
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implemented in include/configs/inka4x0.h .
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II) Approach
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------------
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U-Boot TWserial drivers exports two simple functions and therefore the conversion
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of the driver and creating a core for it is not needed. It should be consolidated
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with include/configs/inka4x0.h and taken to the misc/ dir.
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III) Analysis of in-tree drivers
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--------------------------------
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1) drivers/twserial/soft_tws.c
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------------------------------
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The driver is the only TWserial driver. The ad-hoc part in
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include/configs/inka4x0.h and the core soft_tws driver should be consolidated
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to one compact driver and moved to misc/ .
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