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Date: Thu, 18 Jul 2013 11:48:10 +0200
From: Lars-Peter Clausen <lars@...afoo.de>
To: Oleksandr Kozaruk <oleksandr.kozaruk@...com>
CC: tony@...mide.com, benoit.cousson@...aro.org, rnayak@...com,
peter.ujfalusi@...com, kishon@...com, jic23@....ac.uk,
grant.likely@...aro.org, rob.herring@...xeda.com,
sameo@...ux.intel.com, ch.naveen@...sung.com, poeschel@...onage.de,
milo.kim@...com, balajitk@...com, gg@...mlogic.co.uk,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
linux-iio@...r.kernel.org, devicetree-discuss@...ts.ozlabs.org,
linux-omap@...r.kernel.org
Subject: Re: [PATCH v5 2/2] iio: twl6030-gpadc: TWL6030, TWL6032 GPADC driver
On 07/18/2013 10:36 AM, Oleksandr Kozaruk wrote:
> Hello Lars,
>
> On Wed, Jul 17, 2013 at 9:04 PM, Lars-Peter Clausen <lars@...afoo.de> wrote:
>>> +static int twl6032_calibration(struct twl6030_gpadc_data *gpadc)
>>> +{
>>> + int chn, d1 = 0, d2 = 0, temp;
>>> + u8 trim_regs[17];
>>> + int ret;
>>> +
>>> + ret = twl_i2c_read(TWL6030_MODULE_ID2, trim_regs + 1,
>>> + TWL6030_GPADC_TRIM1, 16);
>>> + if (ret < 0) {
>>> + dev_err(gpadc->dev, "calibration failed\n");
>>> + return ret;
>>> + }
>>> +
>>> + /*
>>> + * Loop to calculate the value needed for returning voltages from
>>> + * GPADC not values.
>>> + *
>>> + * gain is calculated to 3 decimal places fixed point.
>>> + */
>>> + for (chn = 0; chn < TWL6032_GPADC_MAX_CHANNELS; chn++) {
>>> +
>>> + switch (chn) {
>>> + case 0:
>>> + case 1:
>>> + case 2:
>>> + case 3:
>>> + case 4:
>>> + case 5:
>>> + case 6:
>>> + case 11:
>>> + case 12:
>>> + case 13:
>>> + case 14:
>>> + /* D1 */
>>> + d1 = (trim_regs[3] & 0x1F) << 2;
>>> + d1 |= (trim_regs[1] & 0x06) >> 1;
>>> + if (trim_regs[1] & 0x01)
>>> + d1 = -d1;
>>> +
>>> + /* D2 */
>>> + d2 = (trim_regs[4] & 0x3F) << 2;
>>> + d2 |= (trim_regs[2] & 0x06) >> 1;
>>> + if (trim_regs[2] & 0x01)
>>> + d2 = -d2;
>>> + break;
>>> + case 8:
>>> + /* D1 */
>>> + temp = (trim_regs[3] & 0x1F) << 2;
>>> + temp |= (trim_regs[1] & 0x06) >> 1;
>>> + if (trim_regs[1] & 0x01)
>>> + temp = -temp;
>>> +
>>> + d1 = (trim_regs[8] & 0x18) << 1;
>>> + d1 |= (trim_regs[7] & 0x1E) >> 1;
>>> + if (trim_regs[7] & 0x01)
>>> + d1 = -d1;
>>> +
>>> + d1 += temp;
>>> +
>>> + /* D2 */
>>> + temp = (trim_regs[4] & 0x3F) << 2;
>>> + temp |= (trim_regs[2] & 0x06) >> 1;
>>> + if (trim_regs[2] & 0x01)
>>> + temp = -temp;
>>> +
>>> + d2 = (trim_regs[10] & 0x1F) << 2;
>>> + d2 |= (trim_regs[8] & 0x06) >> 1;
>>> + if (trim_regs[8] & 0x01)
>>> + d2 = -d2;
>>> +
>>> + d2 += temp;
>>> + break;
>>> + case 9:
>>> + /* D1 */
>>> + temp = (trim_regs[3] & 0x1F) << 2;
>>> + temp |= (trim_regs[1] & 0x06) >> 1;
>>> + if (trim_regs[1] & 0x01)
>>> + temp = -temp;
>>> +
>>> + d1 = (trim_regs[14] & 0x18) << 1;
>>> + d1 |= (trim_regs[12] & 0x1E) >> 1;
>>> + if (trim_regs[12] & 0x01)
>>> + d1 = -d1;
>>> +
>>> + d1 += temp;
>>> +
>>> + /* D2 */
>>> + temp = (trim_regs[4] & 0x3F) << 2;
>>> + temp |= (trim_regs[2] & 0x06) >> 1;
>>> + if (trim_regs[2] & 0x01)
>>> + temp = -temp;
>>> +
>>> + d2 = (trim_regs[16] & 0x1F) << 2;
>>> + d2 |= (trim_regs[14] & 0x06) >> 1;
>>> + if (trim_regs[14] & 0x01)
>>> + d2 = -d2;
>>> +
>>> + d2 += temp;
>>> + case 10:
>>> + /* D1 */
>>> + d1 = (trim_regs[11] & 0x0F) << 3;
>>> + d1 |= (trim_regs[9] & 0x0E) >> 1;
>>> + if (trim_regs[9] & 0x01)
>>> + d1 = -d1;
>>> +
>>> + /* D2 */
>>> + d2 = (trim_regs[15] & 0x0F) << 3;
>>> + d2 |= (trim_regs[13] & 0x0E) >> 1;
>>> + if (trim_regs[13] & 0x01)
>>> + d2 = -d2;
>>> + break;
>>> + case 7:
>>> + case 18:
>>> + /* D1 */
>>> + temp = (trim_regs[3] & 0x1F) << 2;
>>> + temp |= (trim_regs[1] & 0x06) >> 1;
>>> + if (trim_regs[1] & 0x01)
>>> + temp = -temp;
>>> +
>>> + d1 = (trim_regs[5] & 0x7E) >> 1;
>>> + if (trim_regs[5] & 0x01)
>>> + d1 = -d1;
>>> +.
>>> + d1 += temp;
>>> +
>>> + /* D2 */
>>> + temp = (trim_regs[4] & 0x3F) << 2;
>>> + temp |= (trim_regs[2] & 0x06) >> 1;
>>> + if (trim_regs[2] & 0x01)
>>> + temp = -temp;
>>> +
>>> + d2 = (trim_regs[6] & 0xFE) >> 1;
>>> + if (trim_regs[6] & 0x01)
>>> + d2 = -d2;
>>> +
>>> + d2 += temp;
>>> + break;
>>
>>
>> There is quite a bit of copy paste in here. Putting the bit swizziling into
>> a helper function should also improbe legibility.
>
> Trimming bits are scattered randomly between registers and in
> different bit positions.
> I don't see any commonalities, that could be generalized. as Graeme
> said about it "it's a bane of my life".
The pattern is pretty regular though, how about:
int twl6032_get_trim_value(u8 *trim_regs, unsigned int reg0,
unsigned int reg1, unsigned int mask0, unsigned int mask1,
unsigned int shift0)
{
int val;
val = (trim_regs[reg0] & mask0) << shift0;
val |= (trim_regs[reg1] & mask1) >> 1;
if (trim_regs[reg1] & 0x01)
val = -val;
return val;
}
and then
d1 = twl6032_get_trim_value(trim_regs, 3, 1, 0x1f, 0x06, 2);
d2 = twl6032_get_trim_value(trim_regs, 4, 2, 0x3f, 0x06, 2);
and so on.
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