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-rw-r--r--doc/driver-model/UDM-watchdog.txt334
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+The U-Boot Driver Model Project
+===============================
+Watchdog device subsystem analysis
+==================================
+
+Tomas Hlavacek <tmshlvck@gmail.com>
+2012-03-09
+
+I) Overview
+-----------
+
+U-Boot currently implements an API for HW watchdog devices as explicit drivers
+in drivers/watchdog directory. There are also drivers for both hardware and
+software watchdog on particular CPUs implemented in arch/*/cpu/*/cpu.c. There
+are macros in include/watchdog.h that selects between SW and HW watchdog and
+assembly SW implementation.
+
+The current common interface comprises of one set out of these two possible
+variants:
+
+ 1)
+ void watchdog_reset(void);
+ int watchdog_disable(void);
+ int watchdog_init(void);
+
+ 2)
+ void hw_watchdog_reset(void);
+ void hw_watchdog_init(void);
+
+The watchdog implementations are also spread through board/*/*.c that in
+some cases. The API and semantics is in most cases same as the above
+mentioned common functions.
+
+
+II) Approach
+------------
+
+ 1) New API
+ ----------
+
+ In the UDM each watchdog driver would register itself by a function
+
+ int watchdog_device_register(struct instance *i,
+ const struct watchdog_device_ops *o);
+
+ The structure being defined as follows:
+
+ struct watchdog_device_ops {
+ int (*disable)(struct instance *i);
+ void (*reset)(struct instance *i);
+ };
+
+ The watchdog_init() function will be dissolved into probe() function.
+
+ 2) Conversion thougths
+ ----------------------
+
+ Conversion of watchdog implementations to a new API could be divided
+ to three subsections: a) HW implementations, which are mostly compliant
+ to the above mentioned API; b) SW implementations, which are compliant
+ to the above mentioned API and c) SW implementations that are not compliant
+ to the API and has to be rectified or partially rewritten.
+
+III) Analysis of in-tree drivers
+--------------------------------
+
+ 1) drivers/watchdog/at91sam9_wdt.c
+ ----------------------------------
+ The driver is standard HW watchdog. Simple conversion is possible.
+
+
+ 2) drivers/watchdog/ftwdt010_wdt.c
+ ----------------------------------
+ The driver is ad-hoc HW watchdog. Conversion has to take into account
+ driver parts spread in include/faraday/*. Restructuring the driver and
+ code cleanup has to be considered.
+
+
+ 3) arch/arm/cpu/arm1136/mx31/timer.c
+ ------------------------------------
+ The driver is semi-standard ad-hoc HW watchdog. Conversion has to take
+ into account driver parts spread in the timer.c file.
+
+
+ 4) arch/arm/cpu/arm926ejs/davinci/timer.c
+ -----------------------------------------
+ The driver is ad-hoc semi-standard HW watchdog. Conversion has to take
+ into account driver parts spread in the timer.c file.
+
+
+ 5) arch/arm/cpu/armv7/omap-common/hwinit-common.c
+ -------------------------------------------------
+ The driver is non-standard ad-hoc HW watchdog. Conversion is possible
+ but functions has to be renamed and constants moved to another places.
+
+
+ 6) arch/arm/cpu/armv7/omap3/board.c
+ -----------------------------------
+ The driver is non-standard ad-hoc HW watchdog. Conversion is possible
+ but functions has to be renamed and constants moved to another places.
+
+
+ 7) arch/blackfin/cpu/watchdog.c
+ -------------------------------
+ The driver is standard HW watchdog. Simple conversion is possible.
+
+
+ 8) arch/m68k/cpu/mcf523x/cpu.c
+ ------------------------------
+ The driver is standard HW watchdog. Simple conversion is possible.
+
+
+ 9) arch/m68k/cpu/mcf52x2/cpu.c
+ ------------------------------
+ The driver is standard HW watchdog. Simple conversion is possible.
+
+
+ 10) arch/m68k/cpu/mcf532x/cpu.c
+ -------------------------------
+ The driver is standard HW watchdog. Simple conversion is possible.
+
+
+ 11) arch/m68k/cpu/mcf547x_8x/cpu.c
+ ----------------------------------
+ The driver is standard HW watchdog (there is slight naming convention
+ violation that has to be rectified). Simple conversion is possible.
+
+
+ 12) arch/powerpc/cpu/74xx_7xx/cpu.c
+ -----------------------------------
+ The driver is standard HW watchdog. Simple conversion is possible.
+
+
+ 13) arch/powerpc/cpu/mpc512x/cpu.c
+ ----------------------------------
+ The driver is standard HW watchdog. Simple conversion is possible.
+
+
+ 14) arch/powerpc/cpu/mpc5xx/cpu.c
+ ---------------------------------
+ The driver is standard HW watchdog. Simple conversion is possible.
+
+
+ 15) arch/powerpc/cpu/mpc5xxx/cpu.c
+ ----------------------------------
+ The driver is standard HW watchdog. Simple conversion is possible.
+
+
+ 16) arch/powerpc/cpu/mpc8260/cpu.c
+ ----------------------------------
+ The driver is standard HW watchdog. Simple conversion is possible.
+
+
+ 17) arch/powerpc/cpu/mpc83xx/cpu.c
+ ----------------------------------
+ The driver is standard HW watchdog. Simple conversion is possible.
+
+
+ 18) arch/powerpc/cpu/mpc85xx/cpu.c
+ ----------------------------------
+ The driver is standard HW watchdog. Simple conversion is possible.
+
+
+ 19) arch/powerpc/cpu/mpc86xx/cpu.c
+ ----------------------------------
+ The driver is standard HW watchdog. Simple conversion is possible.
+
+
+ 20) arch/powerpc/cpu/mpc8xx/cpu.c
+
+ The driver is standard HW watchdog. Simple conversion is possible.
+
+
+ 21) arch/powerpc/cpu/ppc4xx/cpu.c
+ ---------------------------------
+ The driver is standard HW watchdog. Simple conversion is possible.
+
+
+ 22) arch/sh/cpu/sh2/watchdog.c
+ ------------------------------
+ The driver is standard HW watchdog. Simple conversion is possible.
+
+
+ 23) arch/sh/cpu/sh3/watchdog.c
+ ------------------------------
+ The driver is standard HW watchdog. Simple conversion is possible.
+
+
+ 24) arch/sh/cpu/sh4/watchdog.c
+ ------------------------------
+ The driver is standard HW watchdog. Simple conversion is possible.
+
+
+ 25) board/amcc/luan/luan.c
+ --------------------------
+ The driver is standard HW watchdog. Simple conversion is possible.
+
+
+ 26) board/amcc/yosemite/yosemite.c
+ ----------------------------------
+ The driver is standard HW watchdog. Simple conversion is possible.
+
+
+ 27) board/apollon/apollon.c
+ ---------------------------
+ The driver is standard HW watchdog however the watchdog_init()
+ function is called in early initialization. Simple conversion is possible.
+
+
+ 28) board/bmw/m48t59y.c
+ -----------------------
+ Special watchdog driver. Dead code. To be removed.
+
+
+ 29) board/davedenx/qong/qong.c
+ ------------------------------
+ The driver is standard HW watchdog. Simple conversion is possible.
+
+
+ 30) board/dvlhost/watchdog.c
+ ----------------------------
+ The driver is standard HW watchdog. Simple conversion is possible.
+
+
+ 31) board/eNET/eNET.c
+ ---------------------
+ The driver is standard HW watchdog. Simple conversion is possible.
+
+
+ 32) board/eltec/elppc/elppc.c
+ -----------------------------
+ The driver is standard HW watchdog. Simple conversion is possible.
+
+
+ 33) board/enbw/enbw_cmc/enbw_cmc.c
+ ----------------------------------
+ Only function proxy call. Code cleanup needed.
+
+
+ 34) board/freescale/mx31pdk/mx31pdk.c
+ -------------------------------------
+ Only function proxy call. Code cleanup needed.
+
+
+ 35) board/gth2/gth2.c
+ ---------------------
+ The driver is standard HW watchdog. Simple conversion is possible.
+
+
+ 36) board/lwmon5/lwmon5.c
+ -------------------------
+ The driver is standard HW watchdog. Simple conversion is possible.
+
+
+ 37) board/manroland/mucmc52/mucmc52.c
+ -------------------------------------
+ The driver is standard HW watchdog. Simple conversion is possible.
+
+
+ 38) board/manroland/uc101/uc101.c
+ ---------------------------------
+ The driver is standard HW watchdog. Simple conversion is possible.
+
+
+ 39) board/mousse/m48t59y.c
+ --------------------------
+ Special watchdog driver. Dead code. To be removed.
+
+
+ 40) board/mvblue/mvblue.c
+ -------------------------
+ The driver is standard HW watchdog. Simple conversion is possible.
+
+
+ 41) board/netphone/netphone.c
+ -----------------------------
+ The driver is standard HW watchdog. Simple conversion is possible.
+
+
+ 42) board/netta/netta.c
+ -----------------------
+ The driver is standard HW watchdog. Simple conversion is possible.
+
+
+ 43) board/netta2/netta2.c
+ -------------------------
+ The driver is standard HW watchdog. Simple conversion is possible.
+
+
+ 44) board/omicron/calimain/calimain.c
+ -------------------------------------
+ Only function proxy call. Code cleanup needed.
+
+
+ 45) board/pcippc2/pcippc2.c
+ ---------------------------
+ The driver is standard HW watchdog. Simple conversion is possible.
+
+
+ 46) board/pcs440ep/pcs440ep.c
+ -----------------------------
+ The driver is standard HW watchdog. Simple conversion is possible.
+
+
+ 47) board/stx/stxxtc/stxxtc.c
+ -----------------------------
+ The driver is standard HW watchdog. Simple conversion is possible.
+
+
+ 48) board/ti/omap2420h4/omap2420h4.c
+ ------------------------------------
+ The driver is standard HW watchdog. Simple conversion is possible.
+
+
+ 49) board/ttcontrol/vision2/vision2.c
+ -------------------------------------
+ The driver is standard HW watchdog but namespace is polluted by
+ non-standard macros. Simple conversion is possible, code cleanup
+ needed.
+
+
+ 50) board/v38b/v38b.c
+ ---------------------
+ The driver is standard HW watchdog. Simple conversion is possible.
+
+
+ 51) board/ve8313/ve8313.c
+ -------------------------
+ The driver is standard HW watchdog. Simple conversion is possible.
+
+
+ 52) board/w7o/watchdog.c
+ ------------------------
+ The driver is standard HW watchdog. Simple conversion is possible.
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