On Mon, Jun 27, 2016 at 8:57 PM, Jonathan Cameron <jic23@xxxxxxxxxx> wrote: > On 27/06/16 08:42, Vlad Dogaru wrote: >> On Wed, Jun 22, 2016 at 10:53:39PM +0200, Linus Walleij wrote: >>> The calibration data is described as coming from an E2PROM and that >>> means it does not change. Just read it once at probe time and store >>> it in the device state container. Also toss the calibration data >>> into the entropy pool since it is device unique. >> >> I think my initial thought when writing this was that regmap will take >> care of the caching and not hit the i2c bus each time. But I don't have >> an issue with this change. Other than that, series looks good to me. > > Good point. I must be half asleep. > > Linus, are we missing something? If not, I'd go without this one. It's true that regmap does cache the contents of the registers, cutting the I2C bus traffic bottleneck. But reading it out every time still incurs a bulk read of 22 bytes from regmap, meaning 22 iterations in regmap where each need to be checked individually for volatileness etc in the regmap core, then this happens at every conversion. Compared to just doing this once and keeping a copy around it is wasteful, so still an optimization worth it IMO. Don't get me wrong, regmap is optimized (just check drivers/base/regmap/*) but it can never be as optimized as reading just once. Also Vlad seems to OK it? Yours, Linus Walleij -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
