[Trac #988] EC code, putchar XON/XOFF handling and crlf conversion

[Zarro Boogs per Child]

#988: EC code, putchar XON/XOFF handling and crlf conversion
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 Reporter:  frief                    |        Owner:  ray.tseng at quantatw.com
     Type:  defect                   |       Status:  new                   
 Priority:  normal                   |    Milestone:  CTest                 
Component:  embedded controller      |   Resolution:                        
 Keywords:  EC uart serial watchdog  |  
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Comment (by frief):

 > Is this a bug/problem?

 Short: no

 Long: It is not a problem in normal operation. Yet, if someone opened the
 case and injected an XOFF at the ISP connector or Pin 24 of the EC (aka
 GPIO07, aka Rx/Bat_Lo) one might be able to force the EC into the endless
 loop (at 0xb245 (firmware ec_vB73) or 0xb53a (firmware ec_vB81)). Sorry
 for the "might" here, someone would have to test or review the C code.

 The watchdog seems to be disabled at least part of the time. Talking in C
 instead of 8051 assembler, there is (in EC firmware ec_vB81) the
 equivalent of WDTCFG = (WDTCFG & 0x80) | 0x48; at addresses 0x7535 and
 0x852a and 0x886f which to my understanding disables the watchdog.
 (Watchdog is enabled at 0x8840).

 There are different levels of paranoia but regardless of whether or not an
 injected XOFF causes a problem, one should probably avoid potentially
 endless loops in microcontroler code unless an (external) watchdog is
 always enabled.

 Greetings,
 Frieder

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Ticket URL: <http://dev.laptop.org/ticket/988#comment:2>
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