Problem trying to measure OMAP35x core temperature

I'm trying to add code to a 2.6.32 kernel to extract the OMAP core temperature for thermal testing, and section 7.4.6 of the OMAP3 TRM (spug98g.pdf) explains the CONTROL_TEMP_SENSOR register.

I've added the following code:

static void omap3logic_fetch_temp(char *temp_buf)

{
    int temp_val;
    unsigned int temp;
    static short temp_table[] = {
        -400, -400, -400, -400,    -400,
        -400, -389, -375, -361, -333, /* 0-9 */
        -318, -304, -290, -275, -261,
        -247, -233, -219, -205, -191, /* 10-19 */
        -177, -163, -149, -134, -120,
        -106,  -92,  -78,  -64,  -50, /* 20-29 */
        -35,   -21,   -7,   +8,  +23,
        +37,   +51,  +66,  +80,  +94, /* 30-39 */
        +108, +123, +137, +151, +165,
        +179, +194, +208, +222, +236, /* 40-49 */
        +251, +265, +279, +293, +307,
        +321, +335, +349, +364, +378, /* 50-59 */
        +392, +406, +420, +424, +449,
        +463, +447, +491, +505, +519, /* 60-69 */
        +533, +546, +560, +574, +588,
        +602, +616, +630, +644, +657, /* 70-79 */
        +671, +685, +699, +713, +727,
        +741, +755, +769, +783, +797, /* 80-89 */
        +811, +823, +838, +852, +865,
        +879, +893, +906, +920, +934, /* 90-99 */
        +947, +961, +975, +989, +1002,
        +1016, +1030, +1043, +1057, +1071, /* 100-109 */
        +1085, +1098, +1112, +1126, +1140,
        +1153, +1167, +1181, +1194, +1208, /* 110-119 */
        +1222, +1235, +1249, +1250, +1250,
        +1250, +1250, +1250, +1250, /* 120-128 */
    };

    temp = omap_ctrl_readl(OMAP343X_CONTROL_TEMP_SENSOR);

    temp_val = (temp_table[temp&0x7f] + temp_table[(temp&0x7f)+1]) / 2;
    sprintf(temp_buf, "%d.%1d (%02x)", temp_val/10, ((unsigned 

int)temp_val)%10, temp);
}

static ssize_t
omap3logic_show_temp(struct class *class, char *buf)

{
    ssize_t retval;
    char temp[128];

    omap3logic_fetch_temp(temp);
    retval = sprintf(buf, "%s\n", temp);
    return retval;
}

static struct class_attribute temp_attr =

    __ATTR(temp, S_IRUGO, omap3logic_show_temp, NULL);

static struct class *omap3logic_temp_class;

void omap3logic_temp_init(void)

{
    int rc;

    omap3logic_temp_class = class_create(THIS_MODULE, "temp");
    if (IS_ERR(omap3logic_temp_class)) {
        printk(KERN_ERR "%s: couldn't create temp class\n", __FUNCTION__);
        return;
    }
    rc = class_create_file(omap3logic_temp_class, &temp_attr);
    if (unlikely(rc)) {
        printk(KERN_ERR "%s: couldn't create temp class file\n", 
__FUNCTION__);
        return;
    }

    /* Set CONTCONV and SOC to start continuous temperature measurements */
    omap_ctrl_writel(0x300, OMAP343X_CONTROL_TEMP_SENSOR);
}

But when I read the register back, I see only a fixed temperature value, even if I fire up some video demos to crank up the load. If I reboot I'll see the temperature jump up, but then it stays constant whether I increase/decrease the CPU load.

Any ideas why this isn't working?

Thanks in advance!

Peter Barada
[email protected]

I have not look at it further but there is some code at
http://thread.gmane.org/gmane.linux.ports.arm.omap/8424/focus=8514.

Hope this helps!

Jean

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