lantiq: fix thermal sensors driver

Read the temperature including the decimale place from the CGU_GPHY1_CR
register.

Decrement the temperature read from the register by 38.0 degree celsius.
The temperature range of the sensor is -38.0 to +154 °C and the register
value 0 is equal to -38.0 °C. This fixes the report of unrealistic
temperatures as seen on all tested boards.

Give the SoC a few milliseconds to get the first temperature value. On
some rare occasions there is no temperature value in the register when
read the first time after activation. This leads to a reported
temperature of -38.0 °C on boot.

Only version 1.2 of the vr9 SoC has a temperature sensor. Add a check
to make sure the driver doesn't load on v1.1 vr9 SoCs.

Signed-off-by: Mathias Kresin <dev@kresin.me>

diff --git a/target/linux/lantiq/patches-4.4/0302-xrx200-add-sensors-driver.patch b/target/linux/lantiq/patches-4.4/0302-xrx200-add-sensors-driver.patch
index 628e476a77bf179c6611fcca45322ae34990c2e1..33ff535881e1391dad611e84ef587da4fd171bb3 100644 (file)
--- a/target/linux/lantiq/patches-4.4/0302-xrx200-add-sensors-driver.patch
+++ b/target/linux/lantiq/patches-4.4/0302-xrx200-add-sensors-driver.patch
@@ -27,7 +27,7 @@
        depends on SPI_MASTER
 --- /dev/null
 +++ b/drivers/hwmon/ltq-cputemp.c
-@@ -0,0 +1,138 @@
+@@ -0,0 +1,154 @@
 +/* Lantiq CPU Temperatur sensor driver for xrx200
 + *
 + * Copyright (C) 2016 Florian Eckert <feckert@tdt.de>
@@ -48,6 +48,7 @@
 +
 +#include <linux/module.h>
 +#include <linux/init.h>
++#include <linux/delay.h>
 +#include <linux/of_device.h>
 +#include <linux/hwmon.h>
 +#include <linux/hwmon-sysfs.h>
@@ -61,6 +62,9 @@
 +static void ltq_cputemp_enable(void)
 +{
 +      ltq_cgu_w32(ltq_cgu_r32(CGU_GPHY1_CR) | CGU_TEMP_PD, CGU_GPHY1_CR);
++
++      /* wait a short moment to let the SoC get the first temperatur value */
++      mdelay(100);
 +}
 +
 +static void ltq_cputemp_disable(void)
@@ -70,8 +74,16 @@
 +
 +static int ltq_cputemp_read(void)
 +{
-+      /* Shift 9 for register alignment and 1 to divide value by 2 */
-+      return (ltq_cgu_r32(CGU_GPHY1_CR) >> 10) & 0xFF;
++      int value;
++
++      /* get the temperature including one decimal place */
++      value = (ltq_cgu_r32(CGU_GPHY1_CR) >> 9) & 0x01FF;
++      value = (value << 2 ) + value;
++
++      /* range -38 to +154 °C, register value zero is -38.0 °C */
++      value -= 380;
++
++      return value;
 +}
 +
 +static ssize_t show_cputemp(struct device *dev,
@@ -81,7 +93,7 @@
 +
 +      value = ltq_cputemp_read();
 +      /* scale temp to millidegree */
-+      value = value * 1000;
++      value = value * 100;
 +
 +      return sprintf(buf, "%d\n", value);
 +}
@@ -101,6 +113,10 @@
 +      int ret;
 +      struct device *hwmon_dev;
 +
++      /* available on vr9 v1.2 SoCs only */
++      if (ltq_soc_type() != SOC_TYPE_VR9_2)
++              return -ENODEV;
++
 +      hwmon_dev = devm_hwmon_device_register_with_groups(&pdev->dev,
 +                                                      "CPU0",
 +                                                      NULL,
@@ -114,7 +130,7 @@
 +
 +      ltq_cputemp_enable();
 +      value = ltq_cputemp_read();
-+      dev_info(&pdev->dev, "Current CPU die temperature: %d °C", value);
++      dev_info(&pdev->dev, "Current CPU die temperature: %d.%d °C", value / 10, value % 10);
 +
 +      return 0;
 +