From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bai Ping Subject: [PATCH] thermal: imx: update the temperature calibration data for imx6 soc Date: Mon, 21 Dec 2015 15:27:56 +0800 Message-ID: <1450682876-26725-1-git-send-email-ping.bai@nxp.com> Mime-Version: 1.0 Content-Type: text/plain Return-path: Received: from mail-am1on0057.outbound.protection.outlook.com ([157.56.112.57]:32002 "EHLO emea01-am1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750799AbbLUIBP (ORCPT ); Mon, 21 Dec 2015 03:01:15 -0500 Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: rui.zhang@intel.com, edubezval@gmail.com Cc: linux-pm@vger.kernel.org According to the design team: After a thorough accuracy study of the Temp sense circuit,we found that with our current equation, an average part can read 7 degrees lower than a known forced temperature. We also found out that the standard variance was around 2C; which is the tightest distribution that we could create. We need to change the temp sense equation to center the average part around the target temperature. Old Equation: Temp = Troom,cal - slope*(Count measured - Count room fuse) Where Troom,cal = 25C and Slope = 0.4297157 - (0.0015974 * Count room fuse) New Equation: Temp = Troom,cal - slope*(Count measured - Count room fuse) +offset Where Troom,cal = 25C and Slope = 0.4148468 - (0.0015423 * Count room fuse) Offset = 3.580661 Signed-off-by: Bai Ping --- drivers/thermal/imx_thermal.c | 20 ++++++++++++-------- 1 file changed, 12 insertions(+), 8 deletions(-) diff --git a/drivers/thermal/imx_thermal.c b/drivers/thermal/imx_thermal.c index c5547bd..9fb613e 100644 --- a/drivers/thermal/imx_thermal.c +++ b/drivers/thermal/imx_thermal.c @@ -69,8 +69,9 @@ enum imx_thermal_trip { #define IMX_PASSIVE_DELAY 1000 #define FACTOR0 10000000 -#define FACTOR1 15976 -#define FACTOR2 4297157 +#define FACTOR1 15423 +#define FACTOR2 4148468 +#define OFFSET 3580661 #define TEMPMON_IMX6Q 1 #define TEMPMON_IMX6SX 2 @@ -385,23 +386,26 @@ static int imx_get_sensor_data(struct platform_device *pdev) * Derived from linear interpolation: * slope = 0.4297157 - (0.0015976 * 25C fuse) * slope = (FACTOR2 - FACTOR1 * n1) / FACTOR0 + * offset = OFFSET / 1000000 * (Nmeas - n1) / (Tmeas - t1) = slope * We want to reduce this down to the minimum computation necessary * for each temperature read. Also, we want Tmeas in millicelsius * and we don't want to lose precision from integer division. So... - * Tmeas = (Nmeas - n1) / slope + t1 - * milli_Tmeas = 1000 * (Nmeas - n1) / slope + 1000 * t1 - * milli_Tmeas = -1000 * (n1 - Nmeas) / slope + 1000 * t1 + * Tmeas = (Nmeas - n1) / slope + t1 + offset + * milli_Tmeas = 1000 * (Nmeas - n1) / slope + 1000 * t1 + OFFSET / 1000 + * milli_Tmeas = -1000 * (n1 - Nmeas) / slope + 1000 * t1 + OFFSET / 1000 * Let constant c1 = (-1000 / slope) - * milli_Tmeas = (n1 - Nmeas) * c1 + 1000 * t1 - * Let constant c2 = n1 *c1 + 1000 * t1 + * milli_Tmeas = (n1 - Nmeas) * c1 + 1000 * t1 + OFFSET / 1000 + * Let constant c2 = n1 *c1 + 1000 * t1 + OFFSET / 1000 * milli_Tmeas = c2 - Nmeas * c1 */ temp64 = FACTOR0; temp64 *= 1000; do_div(temp64, FACTOR1 * n1 - FACTOR2); data->c1 = temp64; - data->c2 = n1 * data->c1 + 1000 * t1; + temp64 = OFFSET; + do_div(temp64, 1000); + data->c2 = n1 * data->c1 + 1000 * t1 + temp64; /* use OTP for thermal grade */ ret = regmap_read(map, OCOTP_MEM0, &val); -- 1.9.1