On 01/12/2015 02:25 PM, Pavel Machek wrote:

Hi!

quoted

quoted

quoted

+struct max77693_sub_led {
+	/* related FLED output identifier */

->flash LED, about 4x.

quoted

+/* split composite current @i into two @iout according to @imax weights */
+static void __max77693_calc_iout(u32 iout[2], u32 i, u32 imax[2])
+{
+	u64 t = i;
+
+	t *= imax[1];
+	do_div(t, imax[0] + imax[1]);
+
+	iout[1] = (u32)t / FLASH_IOUT_STEP * FLASH_IOUT_STEP;
+	iout[0] = i - iout[1];
+}

Is 64-bit arithmetics neccessary here? Could we do the FLASH_IOUT_STEP
divisons before t *=, so that 64-bit division is not neccessary?

It is required. All these operations allow for splitting the composite
current into both outputs according to weights given in the imax
array.

I know.

What about this?

static void __max77693_calc_iout(u32 iout[2], u32 i, u32 imax[2])
{
	u32 t = i;

	t *= imax[1] / FLASH_IOUT_STEP;

Let's consider following case:

t = 1000000
imax[1] = 1000000

multiplication of the above will give 10^12 - much more than
it is possible to encode on 32 bits.

	t = t / (imax[0] + imax[1]);
	t /= FLASH_IOUT_STEP

	iout[1] = (u32)t;
	iout[0] = i - iout[1];
}

Does it lack precision?

Thanks,
									Pavel

-- 
Best Regards,
Jacek Anaszewski