"Gopinath, Thara" <thara@xxxxxx> writes: >>>-----Original Message----- >>>From: Kevin Hilman [mailto:khilman@xxxxxxxxxxxxxxxxxxx] >>>Sent: Thursday, September 16, 2010 8:52 PM >>>To: Gopinath, Thara >>>Cc: linux-omap@xxxxxxxxxxxxxxx; paul@xxxxxxxxx; Sripathy, Vishwanath; Sawant, Anand; Cousson, Benoit >>>Subject: Re: [PATCH 04/13] OMAP: Introduce API to return a device list associated with a voltage >>>domain >>> >>>"Gopinath, Thara" <thara@xxxxxx> writes: >>> >>>[...] >>> >>>>>>> +struct device **opp_init_voltage_params(struct voltagedomain *voltdm, >>>>>>> + int *dev_count) >>>>>>> +{ >>>>>>> + struct device_opp *dev_opp; >>>>>>> + struct device **dev_list; >>>>>>> + int count = 0, i = 0; >>>>>>> + >>>>>>> + list_for_each_entry(dev_opp, &dev_opp_list, node) { >>>>>>> + if (!dev_opp->oh->vdd_name) >>>>>>> + continue; >>>>>>> + >>>>>>> + if (!strcmp(dev_opp->oh->vdd_name, voltdm->name)) { >>>>>>> + dev_opp->oh->voltdm = voltdm; >>>>>> >>>>>>Couldn't we assign the voltdm at opp_add() time since you added it as >>>>>>part of the hwmod? >>>> >>>> We cannot as the voltage layer is not initialized at the point of opp_add. >>>> Having said this, today voltage layer is dependent on opp layer only to figure out >>>> the current nominal voltage from the opp table. If that can be some how decoupled we >>>> can initialize voltage layer early on and implement this. >>> >>>We could decouple the voltage init into and early init and late init to >>>handle this. > > Hello Kevin, > > Yes we could. In fact I do not like the idea of voltage layer > dependent on opp layer itself. So here is my proposal. Maintain a > variable in the main per vdd structure omap_vdd_info curr_volt which > will get updated each time a voltage scale is attempted. OK > Now the only issue is during boot up how does the voltage layer know > what voltage each vdd should be put into ? A piece of code can be > implemented in pm34xx.c/pm44xx.c init functions to read the clock rate > associated with each vdd , call into the opp layer to get the > corresponding voltage ( basically the sequence we do today everytime > in voltage layer when the API to get nominal voltage is called) and > call omap_voltage_scale_vdd with the corresponding voltage. This way > we can fully decouple voltage laye from opp layer and make voltage > init an early_initcall. We might still need a late_initcall to > register debugfs entries though. What is your take on this ? Not sure I fully follow this suggestions, but why not just wait until both OPP and voltage late init are fully done before allowing any voltage scaling? Alternatively, I just did a quick experiment and the device_initcall in pm.c (that initializes the MPU, IVA/DSP and L3 devices, as well as does the OPP layer init) could be made a subsys_initcall, so that by the time SR + voltage are init'd (using device_initcall), OPP layer is fully initialized. Kevin -- 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
