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