Re: [RFC v2 5/6] drivers: boot_constraint: Add initial DT bindings

From: Viresh Kumar
Date: Thu Jul 13 2017 - 01:10:15 EST

On 13-07-17, 10:52, Chen-Yu Tsai wrote:
> I'm afraid the regulator case still doesn't make sense. The voltage
> constraints should be set within each supplies device node. This was
> explained in the discussion in v1 [1].

I thought we were discussing about something I mentioned in one of my example
but never to a point that the regulator problem doesn't exist at all. Perhaps I
misunderstood your concerns. Anyway, lemme try once more with a better example.

Regulator shared by: LCD and MMC (both can do DVFS) and the min/max constraint
that can be set by the consumers of the regulator (both LCD/MMC) are: 1.5 V to
3 V.

The bootloader has programmed the LCD to work at the highest pixel frequency,
which needs the voltage to be in range from 2.5 - 3 V.

Now MMC can get probed first and it can try to bring the voltages below 2.5 V.
Though, 1.5 - 2.5 is a valid range for the LCD, but not at the current pixel

Does that sound like a valid problem?