> -----Original Message----- > From: Shilimkar, Santosh > Sent: Friday, June 24, 2011 6:16 PM > To: Russell King - ARM Linux > Cc: Premi, Sanjeev; linux-omap@xxxxxxxxxxxxxxx; > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx > Subject: Re: [PATCH 2/2] omap2+: pm: cpufreq: Fix > loops_per_jiffy calculation > > Sanjeev, > > On 6/24/2011 4:21 PM, Russell King - ARM Linux wrote: > > On Fri, Jun 24, 2011 at 04:18:31PM +0530, Premi, Sanjeev wrote: > >>> -----Original Message----- > >>> From: Russell King - ARM Linux [mailto:linux@xxxxxxxxxxxxxxxx] > >>> Sent: Friday, June 24, 2011 4:14 PM > >>> To: Premi, Sanjeev > >>> Cc: linux-omap@xxxxxxxxxxxxxxx; > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx > >>> Subject: Re: [PATCH 2/2] omap2+: pm: cpufreq: Fix > >>> loops_per_jiffy calculation > >>> > >>> On Fri, Jun 24, 2011 at 04:05:42PM +0530, Sanjeev Premi wrote: > >>>> Currently, loops_per_jiffy is being calculated before calling > >>>> cpufreq_notify_transition(). > >>>> > >>>> However, generic cpufreq driver adjusts the jiffies as well. > >>>> Double adjustment leads to incorrect value being assigned to > >>>> loops_per_jiffy. > >>> > >>> Are you sure the generic cpufreq driver adjusts the per-cpu > >>> loops_per_jiffy > >>> values? I don't believe it does. > >> > >> Russell, > >> > >> I am quoting the function from drivers/cpufreq/cpufreq.h > >> Follow the arrows: > > > > Let's go to war with quotes then, because clearly you > haven't read the code > > properly: > > > > | #ifndef CONFIG_SMP > > ^^^^^^^^^^^^^^^^^^^^^ > > | static unsigned long l_p_j_ref; > > | static unsigned int l_p_j_ref_freq; > > | > > | static void adjust_jiffies(unsigned long val, struct > cpufreq_freqs *ci) > > | { > > | ... code to adjust jiffies ... > > | } > > | #else > > | static inline void adjust_jiffies(unsigned long val, > struct cpufreq_freqs *ci) > > | { > > | return; > > | } > > | #endif > > > > Notice how if CONFIG_SMP is set, adjust_jiffies becomes a > no-op. So if > > CONFIG_SMP=y, loops_per_jiffy will _not_ be scaled by core code. > > > As Russell rightly pointed out, you need to take care of > UP/SMP and UP > OVER SMP. > > The generic code updates in only in case of UP build. I thought, the > comment is the code was well explaining that part. [sp] I did read the code but took long to understand most of it. Hence patch 1 of this series. I already accepted that I didn't notice definition of adjust_jiffies. ...call it perils of leaving job half-done across a good-night-sleep! As is, the calculations of UP are incorrect... which I was fixing. Anyway, I have an updated patch - currently testing with CONFIG_SMP enabled. Will be posting soon. ~sanjeev > > Regards > Santosh > -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
