On 12/21/2013 09:30 AM, Jean Delvare wrote:
Hi Guenter, hi Anthony,
On Thu, 19 Dec 2013 10:10:49 -0800, Guenter Roeck wrote:
On Thu, Dec 19, 2013 at 03:54:54PM +0100, Jean Delvare wrote:
BTW, you (and we) probably shouldn't waste too much energy on this.
ADCs are only accurate to some degree anyway. If you take the
components connected to the input into consideration, the accuracy gets
even worse. For example, if the input voltage must be scaled down to
fit in the ADC's range, you need at least one resistor, which in best
cases will have a 1% accurate value (known as tolerance.) That's ten
times the LSB of your 10-bit ADC, at which point / 1023 or / 1024
really makes no practical difference. Sub-percent tolerant resistors are
expensive and rare in consumer electronics in my experience.
True, but on the other side (and after looking into the datasheet)
the driver already calculated the voltage on adc4..6 correctly,
so unless you disagree I would like to apply the hwmon patch to -next
for consistency.
The datasheet isn't the best quality I've seen. The gain values
mentioned to not even match the formulas in the same cell... But I can't
object to implementing conversions the way the datasheet says, no
matter how suspicious.
I don't really know what tree the patch is based on. Anthony said
linux-next but I can't see ichg_reg_to_mA there.
I didn't check the power patch, but the hwmon patch applied cleanly to
the current upstream.
If volt_reg_to_mv is updated then you certainly want to update
vbbat_reg_to_mv the same way, as it diverges from the datasheet just
the same.
He is doing that in the hwmon patch. I don't see vbbat_reg_to_mv()
in the power driver, at least not in the upstream version.
Also, please update Documentation/hwmon/da9052 so that the
documentation matches the actual driver code.
You are right, that needs to be updated as well.
I really would like to hear what David Dajun Chen has to say about
that. He must have had a reason to use different conversions formulas
than the datasheet specifies.
Hmm ... if this was done on purpose, I'd like to see a comment somewhere
describing why the formula in the datasheet isn't used, to avoid this kind
of back-and-forth in the future.
Thanks,
Guenter
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