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Date: Sun, 29 Nov 2015 21:25:53 +1100 (AEDT) From: Finn Thain <fthain@...egraphics.com.au> To: Geert Uytterhoeven <geert@...ux-m68k.org> cc: Ondrej Zary <linux@...nbow-software.org>, "James E.J. Bottomley" <JBottomley@...n.com>, Michael Schmitz <schmitzmic@...il.com>, Linux/m68k <linux-m68k@...r.kernel.org>, scsi <linux-scsi@...r.kernel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org> Subject: Re: [PATCH 22/71] ncr5380: Eliminate selecting state On Sun, 29 Nov 2015, Geert Uytterhoeven wrote: > This still heavily depends on the processing time spent in > NCR5380_read(). You should never use a value derived from > loops_per_jiffy for a non-empty loop, Sure but the time-out condition isn't supposed to be precise. Plus/minus a jiffy is no problem. Plus/minus a second is no good. > as it may take much longer. Always compare with an maximum end time > instead. That can't work with interrupts disabled, which was the problem I was trying to solve by use of loops_per_jiffy. NCR5380_poll_politely() in mainline doesn't work with interrupts disabled either, hence patch 21. > > E.g.: > > end = jiffies + 2; /* 1 jiffie + 1 safeguard */ > do { > if ((NCR5380_read(reg1) & bit1) == val1) > return 0; > cpu_relax(); > } while (time_before(jiffies, end); > > And a similar loop for "Busy-wait for up to 20 ms". Interrupts may be disabled during that loop also. Please refer to (and/or respond to) patch 21, "ncr5380: Sleep when polling, if possible", in which these changes were made. -- > > Gr{oetje,eeting}s, > > Geert > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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