Re: [PATCH v3] thermal: rockchip: make temperature reporting much more accurate

From: Caesar Wang
Date: Wed Jan 21 2015 - 23:59:05 EST



å 2015å01æ22æ 12:25, Daniel Kurtz åé:
On Thu, Jan 22, 2015 at 12:21 PM, Caesar Wang
<caesar.wang@xxxxxxxxxxxxxx> wrote:
å 2015å01æ22æ 12:01, Daniel Kurtz åé:

On Thu, Jan 22, 2015 at 1:29 AM, Caesar Wang <wxt@xxxxxxxxxxxxxx> wrote:
In general, the kernel should report temperature readings exactly as
reported by the hardware. The cpu / gpu thermal driver works in 5 degree
increments,but we ought to do more accurate. The temperature will do
linear interpolation between the entries in the table.

Test= $md5sum /dev/zero &
$while true; do grep "" /sys/class/thermal/thermal_zone[1-2]/temp;
sleep .5; done

e.g. We can get the result as follows:
/sys/class/thermal/thermal_zone1/temp:39994
/sys/class/thermal/thermal_zone2/temp:39086
/sys/class/thermal/thermal_zone1/temp:39994
/sys/class/thermal/thermal_zone2/temp:39540
/sys/class/thermal/thermal_zone1/temp:39540
/sys/class/thermal/thermal_zone2/temp:39540
/sys/class/thermal/thermal_zone1/temp:39540
/sys/class/thermal/thermal_zone2/temp:39994

Signed-off-by: Caesar Wang <wxt@xxxxxxxxxxxxxx>
Reviewed-by: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>

---

Changes in v3:
Suggested-by Daniel Kurtz,
the check doesn't reject "code == 0xfff"
Fixed in rk_tsadcv2_code_to_temp(u32 code)

Changes in v2:
Reviewed-by: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>

drivers/thermal/rockchip_thermal.c | 32
++++++++++++++++++++++----------
1 file changed, 22 insertions(+), 10 deletions(-)

diff --git a/drivers/thermal/rockchip_thermal.c
b/drivers/thermal/rockchip_thermal.c
index 1bcddfc..ce18007 100644
--- a/drivers/thermal/rockchip_thermal.c
+++ b/drivers/thermal/rockchip_thermal.c
@@ -193,19 +193,22 @@ static u32 rk_tsadcv2_temp_to_code(long temp)

static long rk_tsadcv2_code_to_temp(u32 code)
{
- int high, low, mid;
-
- low = 0;
- high = ARRAY_SIZE(v2_code_table) - 1;
- mid = (high + low) / 2;
+ unsigned int low = 0;
+ unsigned int high = ARRAY_SIZE(v2_code_table) - 1;
+ unsigned int mid = (low + high) / 2;
+ unsigned int num;
+ unsigned long denom;

+ /* No code available, return callback */
if (code > v2_code_table[low].code || code <
v2_code_table[high].code)
- return 125000; /* No code available, return max
temperature */
+ return rk_tsadcv2_code_to_temp(code);
Isn't this an infinite recursion?

No, I think we can try check if it is happened.
Maybe we can return a warning/error for it.
I mean, if the 'if' condition is true, then this will just call the
same function again with the same code, and again, and again...
Just return an error code here, -ENOENT maybe?
I am not sure what error code is appropriate.

Maybe "return -EAGAIN"

while (low <= high) {
- if (code >= v2_code_table[mid].code && code <
- v2_code_table[mid - 1].code)
- return v2_code_table[mid].temp;
+ if (code >= v2_code_table[mid].code &&
+ code < v2_code_table[mid - 1].code)
+ break;
+ else if (code == TSADCV2_DATA_MASK)
+ break;
else if (code < v2_code_table[mid].code)
low = mid + 1;
else
@@ -213,7 +216,16 @@ static long rk_tsadcv2_code_to_temp(u32 code)
mid = (low + high) / 2;
}

- return 125000;
+ /*
+ * The 5C granularity provided by the table is too much. Let's
+ * assume that the relationship between sensor readings and
+ * temperature between 2 table entries is linear and interpolate
+ * to produce less granular result.
+ */
+ num = v2_code_table[mid].temp - v2_code_table[mid - 1].temp;
+ num *= v2_code_table[mid - 1].code - code;
+ denom = v2_code_table[mid - 1].code - v2_code_table[mid].code;
+ return v2_code_table[mid - 1].temp + (num / denom);
}

/**
--
1.9.1



--
Best regards
Caesar Wang (çæè)
çåçèåçåæéåå
Fuzhou Rockchip Electronics Co.Ltd
çåççååéçèèäåé89åèäåAå18åæ(350003)
Addr:No.18 Building, A District, No.89, software Boulevard Fuzhou,
Fujian,PRC
Email:wxt@xxxxxxxxxxxxxx
Tel:+86-591-83991906/07->8221


_______________________________________________
Linux-rockchip mailing list
Linux-rockchip@xxxxxxxxxxxxxxxxxxx
http://lists.infradead.org/mailman/listinfo/linux-rockchip


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/