> -----Original Message----- > From: u-boot-boun...@lists.denx.de [mailto:u-boot-boun...@lists.denx.de] > On Behalf Of Wolfgang Denk > Sent: Tuesday, October 26, 2010 10:59 AM > To: Reinhard Meyer > Cc: Menon, Nishanth; u-boot > Subject: Re: [U-Boot] [PATCH v2] mmc: omap: timeout counter fix > > Dear Reinhard Meyer, > > In message <4cc62b6c.30...@emk-elektronik.de> you wrote: > > > > In such cases I prefer to use: > > > > uint64_t etime; > > ... > > etime = get_ticks() + get_tbclk(); /* 1 second */ > > do { > > whatever; > > udelay (xx); > > } while (condition && get_ticks() <= etime); > > > > That is far more accurate than calling udelay() 100000 times. > > It may be more accuratre, but it may also be HORRIBLY WRONG!! > > Do NOT do that!! NEVER implement such a delay loop as > > end = time() + delay; > while (time() < end) > ... > > It fails in case the timer wraps around. > > Assume 32 bit counters, start time = 0xFFFFFFF0, delay = 0x20. It > will compute end = 0x10, the while codition is immediately false, and > you don't have any delay at all, which most probably generates a > false error condition. > > > Correct implementation of a timeout like that should always look like > that: > > start = time(); > while ((time() - start) < delay) > ... > > This works much better (assuming unsigned arithmetics). [Ghorai] Thanks.. This is the best approach. Otherwise udelay() will increase the boot time.
> > Best regards, > > Wolfgang Denk > > -- > DENX Software Engineering GmbH, MD: Wolfgang Denk & Detlev Zundel > HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany > Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: w...@denx.de > Ein weiser Herrscher kann in einem großen Land mehr Gutes bewirken > als in einem kleinen - ein dummer Herrscher aber auch viel mehr Un- > fug. Da weise Herrscher seltener sind als dumme, war ich schon immer > gegen große Reiche skeptisch. - Herbert Rosendorfer > _______________________________________________ > U-Boot mailing list > U-Boot@lists.denx.de > http://lists.denx.de/mailman/listinfo/u-boot _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
