On Fri, Nov 13, 2015 at 11:26:37AM +0000, Javi Merino wrote: > On Fri, Nov 13, 2015 at 11:09:12AM +0100, Sascha Hauer wrote: > > On Wed, Nov 11, 2015 at 08:27:47AM +0100, Sascha Hauer wrote: > > > On Tue, Nov 10, 2015 at 10:26:30AM -0800, Eduardo Valentin wrote: > > > > On Tue, Nov 10, 2015 at 12:05:54PM +0000, Javi Merino wrote: > > > > > On Mon, Nov 09, 2015 at 11:13:32AM +0100, Sascha Hauer wrote: > > > > > > > > <cut> > > > > > > > > > > + > > > > > > +/* > > > > > > + * The MT8173 thermal controller has four banks. Each bank can read up to > > > > > > + * four temperature sensors simultaneously. The MT8173 has a total of 5 > > > > > > + * temperature sensors. We use each bank to measure a certain area of the > > > > > > + * SoC. Since TS2 is located centrally in the SoC it is influenced by multiple > > > > > > + * areas, hence is used in different banks. > > > > > > + */ > > > > > > +static const struct mtk_thermal_bank_cfg bank_data[] = { > > > > > > + { > > > > > > + .num_sensors = 2, > > > > > > + .sensors = { MT8173_TS2, MT8173_TS3 }, > > > > > > + }, { > > > > > > + .num_sensors = 2, > > > > > > + .sensors = { MT8173_TS2, MT8173_TS4 }, > > > > > > + }, { > > > > > > + .num_sensors = 3, > > > > > > + .sensors = { MT8173_TS1, MT8173_TS2, MT8173_TSABB }, > > > > > > + }, { > > > > > > + .num_sensors = 1, > > > > > > + .sensors = { MT8173_TS2 }, > > > > > > + }, > > > > > > +}; > > > > > > > > Would it make sense to simply expose all sensors and let the > > > > configuration of their aggregation be done by DT? > > > > > > This particular layout has been chosen because there's also the Smart > > > Voltage Scaler (SVS) in the SoC. The SVS uses the same banks for > > > measuring temperatures. I don't know the details yet, I just asked the > > > Mediatek guys. > > > > Ok, the job of the SVS is to always pick the best voltage for a given > > CPU frequency based on the temperature of the CPU cluster. How I > > understand it the SVS engine automatically reads temperatures from bank0 > > for the first CPU cluster and from bank1 for the second CPU cluster. For > > this to work we are not free to assign the sensors to the banks > > arbitrarily. > > > > I was told that controlling the CPU frequency the performance is better > > if we use the maximum temperature of the whole die rather than the > > temperature of individual clusters. > > > > I would prefer to keep the sensor/bank association like it currently is > > as it allows for easy SVS engine integration. Also I would prefer to > > expose a single thermal zone for now, it will be easier to add > > additional zones later than it is to remove them later once we have > > exposed them to the device tree. > > > > Is that ok with you? > > Fair enough. I agree that it's easier to add thermal zones in the > future than to remove it. Thanks for the explanation. I added this comment to make this a bit clearer for the next version: /* * The thermal core only gets the maximum temperature of all banks, so * the bank concept wouldn't be necessary here. However, the SVS (Smart * Voltage Scaling) unit makes its decisions based on the same bank * data, and this indeed needs the temperatures of the individual * banks * for making better decisions. */ -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html