Tested-by: Leo Liu <redacted>

Best Regards,
Leo

-----Original Message-----
From: Ping Bai
Sent: Monday, January 04, 2016 3:33 PM
To: Eduardo Valentin
Cc: rui.zhang@intel.com; linux-pm@vger.kernel.org; Fuchuan Liu;
tharvey@gateworks.com
Subject: RE: [PATCH] thermal: imx: update the temperature calibration data for
imx6 soc

quoted

-----Original Message-----
From: Eduardo Valentin [mailto:edubezval@gmail.com]
Sent: 2016年1月1日 1:51
To: Ping Bai <ping.bai@nxp.com>
Cc: rui.zhang@intel.com; linux-pm@vger.kernel.org
Subject: Re: [PATCH] thermal: imx: update the temperature calibration
data for
imx6 soc

On Mon, Dec 21, 2015 at 03:27:56PM +0800, Bai Ping wrote:

quoted

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.

quoted

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 <ping.bai@nxp.com>
---
 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)

quoted

 	 * 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

quoted

 	 * 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;

Dear Bai Ping. Can you please get at least on Tested-by response in
the mailing list for this patch from one of your co-workers, for example?

CC: Fuchuan liu,  he is responsible for testing it.

quoted

Meanwhile, a couple of questions:

Does this offset work well on all chip distribution?

Yes, this offset is for all chip distribution.

quoted

Do we need a different offset for different soc revision ? Is the same
offset applicable to IMX6Q and to IMX6SX?

Yes, The same offset for all i.MX6 OSC.

quoted

I strong recommend you to translate this driver to add of-thermal
support. This is more than desirable, specially considering the type
of changes you are in a need, such as the one above. This is better
described in DT, not in the driver code.

you are right, using of-thermal is a best way, I have tried to refactor this driver
to support of-thermal, but there are two issues that are not easy to tackle, one
is in the original driver, everytime we modified the 'passive' trip point
temp(set_trip_temp), we will update the high_alarm value correspondingly,
using 'of-thermal' support, this function seems be broken. Another issue is that
Tim Harvey [off-list ref] add temperature grade check in
commit a2291badc355d5, if using of-thermal, this part of function will be not
easy to tackle. look forward to your comments and suggestions.

quoted

quoted

 	/* use OTP for thermal grade */
 	ret = regmap_read(map, OCOTP_MEM0, &val);
--
1.9.1