Re: [PATCH v5 2/2] iio: twl6030-gpadc: TWL6030, TWL6032 GPADC driver

[Oleksandr Kozaruk <oleksandr.kozaruk-hExfYMNmJl/Cnp4W7fqMDg@public.gmane.org>]

Hello Lars,

On Thu, Jul 18, 2013 at 12:48 PM, Lars-Peter Clausen <lars-Qo5EllUWu/uELgA04lAiVw@public.gmane.org> wrote:
> 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-Qo5EllUWu/uELgA04lAiVw@public.gmane.org> 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.

Thank you. I think legibility is better now, I even found a bug - in
case 9 'break' was missing.
Though it is not without special case for channels 7, 18:
	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 = twl6032_get_trim_value(trim_regs, 3, 1, 0x1f, 0x06, 2);
			d2 = twl6032_get_trim_value(trim_regs, 4, 2, 0x3f, 0x06, 2);
			break;
		case 8:
			temp = twl6032_get_trim_value(trim_regs, 3, 1, 0x1f, 0x06, 2);
			d1 = temp + twl6032_get_trim_value(trim_regs, 8, 7, 0x18, 0x1E, 1);

			temp = twl6032_get_trim_value(trim_regs, 4, 2, 0x3F, 0x06, 2);
			d2 = temp + twl6032_get_trim_value(trim_regs, 10, 8, 0x1F, 0x06, 2);
			break;
		case 9:
			temp = twl6032_get_trim_value(trim_regs, 3, 1, 0x1f, 0x06, 2);
			d1 = temp + twl6032_get_trim_value(trim_regs, 14, 12, 0x18, 0x1E, 1);

			temp = twl6032_get_trim_value(trim_regs, 4, 2, 0x3f, 0x06, 2);
			d2 = temp + twl6032_get_trim_value(trim_regs, 16, 14, 0x1F, 0x06, 1);
			break;
		case 10:
			d1 = twl6032_get_trim_value(trim_regs, 11, 9, 0x0f, 0x0E, 3);
			d2 = twl6032_get_trim_value(trim_regs, 15, 13, 0x0f, 0x0E, 3);
			break;
		case 7:
		case 18:
			temp = twl6032_get_trim_value(trim_regs, 3, 1, 0x1f, 0x06, 2);

			d1 = (trim_regs[5] & 0x7E) >> 1;
			if (trim_regs[5] & 0x01)
				d1 = -d1;
			d1 += temp;

			temp = twl6032_get_trim_value(trim_regs, 4, 2, 0x3f, 0x06, 2);

			d2 = (trim_regs[6] & 0xFE) >> 1;
			if (trim_regs[6] & 0x01)
				d2 = -d2;

			d2 += temp;
			break;
		default:
			/* No data for other channels */
			continue;
		}

-- 
Regards,
Oleksandr Kozaruk