> -----Original Message----- > From: Russell King - ARM Linux [mailto:li...@arm.linux.org.uk] > Sent: Friday, June 24, 2011 8:42 PM > To: Premi, Sanjeev > Cc: linux-omap@vger.kernel.org; linux-arm-ker...@lists.infradead.org > Subject: Re: [PATCHv2] omap2+: pm: cpufreq: Fix > loops_per_jiffy calculation > > Right, thanks for the file. Here's the patch. > > --- omap2plus-cpufreq.c~ 2011-06-24 15:50:32.000000000 +0100 > +++ omap2plus-cpufreq.c 2011-06-24 16:00:08.000000000 +0100 > @@ -44,6 +44,16 @@ > static char *mpu_clk_name; > static struct device *mpu_dev; > > +#ifdef CONFIG_SMP > +struct lpj_info { > + unsigned long ref; > + unsigned int freq; > +}; > + > +static DEFINE_PER_CPU(struct lpj_info, lpj_ref); > +static struct lpj_info global_lpj_ref; > +#endif > + > static int omap_verify_speed(struct cpufreq_policy *policy) > { > if (!freq_table) > @@ -109,14 +119,25 @@ > freqs.new = omap_getspeed(policy->cpu); > > #ifdef CONFIG_SMP > - /* Adjust jiffies before transition */ > + /* Adjust per-cpu loops_per_jiffy before transition */ > for_each_cpu(i, policy->cpus) { > - unsigned long lpj = per_cpu(cpu_data, > i).loops_per_jiffy; > - > - per_cpu(cpu_data, i).loops_per_jiffy = > cpufreq_scale(lpj, > - freqs.old, > - freqs.new); > + struct lpj_info *lpj = &per_cpu(lpj_ref, i); > + if (!lpj->freq) { > + lpj->ref = per_cpu(cpu_data, i).loops_per_jiffy; > + lpj->freq = freqs.old; > + } > + > + per_cpu(cpu_data, i).loops_per_jiffy = > + cpufreq_scale(lpj->ref, lpj->freq, freqs.new); > + } > + > + /* And don't forget to adjust the global one */ > + if (!global_lpj_ref.freq) { > + global_lpj_ref.ref = loops_per_jiffy; > + global_lpj_ref.freq = freqs.old; > } > + loops_per_jiffy = cpufreq_scale(global_lpj_ref.ref, > global_lpj_ref.freq, > + freqs.new); > #endif > > /* Notify transitions */ > > > Notice how we adjust _both_ the per-cpu loops_per_jiffy, and that we > adjust them with reference to the initial values. > > If you adjust lpj with reference to the last, then you _will_ build up > a progressively bigger and bigger error in the value over time.
Russell, I definitely didn't see so many things through your comments. But that may just be reflection of my naivety with SMP! I am currently testing another patch for beagle - will apply and test on OMAP3EVM (just to be sure). Can I include it in my next patch rev? ~sanjeev -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
