| Submitter | Carl-Daniel Hailfinger |
|---|---|
| Date | 2010-03-06 03:28:35 |
| Message ID | <4B91CBE3.4040306@gmx.net> |
| Download | mbox | patch |
| Permalink | /patch/1016/ |
| State | Accepted |
| Commit | r986 |
| Headers | show |
Comments
Ping? This cleanup is part 1/2 to make flashrom work with clang and unbreak the delay calculation. If the new style code is OK, I'll submit part 2/2 which makes heavy use of the new style code to get timing accuracy of +-10% even in case of CPU speed variations. Considering that the current code relies on the dumbness of the optimizer in the C compiler and still manages to make all delays twice as long as intended, I hope we can get the fixed code in before 0.9.2. On 06.03.2010 04:28, Carl-Daniel Hailfinger wrote: > Note: This patch is the first step towards a better delay loop > calibration which will work regardless of how smart the C compiler is. > > Clean up code duplication and measure timing of 10/100/1000/10000 us delays. > Add copyright notices for my past and current work on this file. > > If possible, please run the following command a few times and mail the > output to flashrom@flashrom.org > flashrom -V|grep delay > Regards, Carl-Daniel
On Wed, 24 Mar 2010, Carl-Daniel Hailfinger wrote: > Ping? > This cleanup is part 1/2 to make flashrom work with clang and unbreak > the delay calculation. > If the new style code is OK, I'll submit part 2/2 which makes heavy use > of the new style code to get timing accuracy of +-10% even in case of > CPU speed variations. Considering that the current code relies on the > dumbness of the optimizer in the C compiler and still manages to make > all delays twice as long as intended, I hope we can get the fixed code > in before 0.9.2. Imo looks fine, on one machine and nic3com i get Calibrating delay loop... 95M loops per second, 10 myus = 23 us, 100 myus = 202 us, 1000 myus = 2042 us, 10000 myus = 20020 us, OK. same machine but mainboard interface (internal) Calibrating delay loop... 94M loops per second, 10 myus = 23 us, 100 myus = 199 us, 1000 myus = 1972 us, 10000 myus = 19784 us, OK. still bit far from 10uS = 10myus anyway i think it won't break anything Acked-by: Maciej Pijanka <maciej.pijanka@gmail.com> > > On 06.03.2010 04:28, Carl-Daniel Hailfinger wrote: > > Note: This patch is the first step towards a better delay loop > > calibration which will work regardless of how smart the C compiler is. > > > > Clean up code duplication and measure timing of 10/100/1000/10000 us delays. > > Add copyright notices for my past and current work on this file. > > > > If possible, please run the following command a few times and mail the > > output to flashrom@flashrom.org > > flashrom -V|grep delay > > > > Regards, > Carl-Daniel >
On 27.03.2010 14:35, Maciej Pijanka wrote: > On Wed, 24 Mar 2010, Carl-Daniel Hailfinger wrote: > >> This cleanup is part 1/2 to make flashrom work with clang and unbreak >> the delay calculation. >> If the new style code is OK, I'll submit part 2/2 which makes heavy use >> of the new style code to get timing accuracy of +-10% even in case of >> CPU speed variations. Considering that the current code relies on the >> dumbness of the optimizer in the C compiler and still manages to make >> all delays twice as long as intended, I hope we can get the fixed code >> in before 0.9.2. >> > > Imo looks fine, > on one machine and nic3com i get > Calibrating delay loop... 95M loops per second, 10 myus = 23 us, 100 myus = 202 us, 1000 myus = 2042 us, 10000 myus = 20020 us, OK. > same machine but mainboard interface (internal) > Calibrating delay loop... 94M loops per second, 10 myus = 23 us, 100 myus = 199 us, 1000 myus = 1972 us, 10000 myus = 19784 us, OK. > > still bit far from 10uS = 10myus > Indeed. That's a code bug I'll deal with in the next patch. > anyway i think it won't break anything > > Acked-by: Maciej Pijanka <maciej.pijanka@gmail.com> > Thanks, committed in r986. Regards, Carl-Daniel
Patch
Index: flashrom-delayloop/udelay.c =================================================================== --- flashrom-delayloop/udelay.c (Revision 921) +++ flashrom-delayloop/udelay.c (Arbeitskopie) @@ -2,6 +2,7 @@ * This file is part of the flashrom project. * * Copyright (C) 2000 Silicon Integrated System Corporation + * Copyright (C) 2009,2010 Carl-Daniel Hailfinger * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by @@ -19,6 +20,8 @@ */ #include <sys/time.h> +#include <stdlib.h> +#include <limits.h> #include "flash.h" // count to a billion. Time it. If it's < 1 sec, count to 10B, etc. @@ -30,21 +33,30 @@ for (i = 0; i < usecs * micro; i++) ; } +unsigned long measure_delay(int usecs) +{ + unsigned long timeusec; + struct timeval start, end; + + gettimeofday(&start, 0); + myusec_delay(usecs); + gettimeofday(&end, 0); + timeusec = 1000000 * (end.tv_sec - start.tv_sec) + + (end.tv_usec - start.tv_usec); + + return timeusec; +} + void myusec_calibrate_delay(void) { int count = 1000; unsigned long timeusec; - struct timeval start, end; int ok = 0; printf("Calibrating delay loop... "); while (!ok) { - gettimeofday(&start, 0); - myusec_delay(count); - gettimeofday(&end, 0); - timeusec = 1000000 * (end.tv_sec - start.tv_sec) + - (end.tv_usec - start.tv_usec); + timeusec = measure_delay(count); count *= 2; if (timeusec < 1000000 / 4) continue; @@ -53,14 +65,18 @@ // compute one microsecond. That will be count / time micro = count / timeusec; + msg_pdbg("%ldM loops per second, ", micro); - gettimeofday(&start, 0); - myusec_delay(100); - gettimeofday(&end, 0); - timeusec = 1000000 * (end.tv_sec - start.tv_sec) + - (end.tv_usec - start.tv_usec); - printf_debug("%ldM loops per second, 100 myus = %ld us. ", - (unsigned long)micro, timeusec); + /* We're interested in the actual precision. */ + timeusec = measure_delay(10); + msg_pdbg("10 myus = %ld us, ", timeusec); + timeusec = measure_delay(100); + msg_pdbg("100 myus = %ld us, ", timeusec); + timeusec = measure_delay(1000); + msg_pdbg("1000 myus = %ld us, ", timeusec); + timeusec = measure_delay(10000); + msg_pdbg("10000 myus = %ld us, ", timeusec); + printf("OK.\n"); }
Note: This patch is the first step towards a better delay loop calibration which will work regardless of how smart the C compiler is. The delay loop is probably one of the oldest pieces of code in flashrom and it shows. Clean up code duplication and measure timing of 10/100/1000/10000 us delays. Add copyright notices for my past and current work on this file. If possible, please run the following command a few times and mail the output to flashrom@flashrom.org flashrom -V|grep delay Signed-off-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@gmx.net>