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authorTomáš Hlaváček <tmshlvck@gmail.com>2012-08-08 13:42:30 +0200
committerWolfgang Denk <wd@denx.de>2012-09-02 18:00:02 +0200
commitbfae89abf10e3dc52504e7f7f91d5eaf8e320cd3 (patch)
treea813b08e8d7287e939d2408d5503db0805932633
parent0d9e59948a6694ac5f5bb08fd9537732b76bceb3 (diff)
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dm: Add twserial device document
Signed-off-by: Tomas Hlavacek<tmshlvck@gmail.com>
-rw-r--r--doc/driver-model/UDM-twserial.txt47
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diff --git a/doc/driver-model/UDM-twserial.txt b/doc/driver-model/UDM-twserial.txt
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+==================================
+TWserial device subsystem analysis
+==================================
+
+Tomas Hlavacek<tmshlvck@gmail.com>
+2012-03-21
+
+I) Overview
+-----------
+
+U-Boot currently implements one common API for TWSerial devices. The interface
+is defined in include/tws.h and comprises of functions:
+
+ int tws_read(uchar *buffer, int len);
+ int tws_write(uchar *buffer, int len);
+
+The functions are implemented by a proper device driver in drivers/twserial
+directory and the driver to be compiled in is selected in a Makefile. There is
+only one driver present now.
+
+The driver depends on ad-hoc code in board specific data, namely functions:
+
+ void tws_ce(unsigned bit);
+ void tws_wr(unsigned bit);
+ void tws_clk(unsigned bit);
+ void tws_data(unsigned bit);
+ unsigned tws_data_read(void);
+ void tws_data_config_output(unsigned output);
+
+implemented in include/configs/inka4x0.h .
+
+II) Approach
+------------
+
+ U-Boot TWserial drivers exports two simple functions and therefore the conversion
+ of the driver and creating a core for it is not needed. It should be consolidated
+ with include/configs/inka4x0.h and taken to the misc/ dir.
+
+
+III) Analysis of in-tree drivers
+--------------------------------
+
+ 1) drivers/twserial/soft_tws.c
+ ------------------------------
+ The driver is the only TWserial driver. The ad-hoc part in
+ include/configs/inka4x0.h and the core soft_tws driver should be consolidated
+ to one compact driver and moved to misc/ .