Re: [Freedreno] [v1] drm/msm/dsi/pll: call vco set rate explicitly

harigovi
2020-02-07T12:38:47Z

On 2020-02-06 20:29, Jeffrey Hugo wrote:
> On Thu, Feb 6, 2020 at 2:13 AM Harigovindan P <harigovi@codeaurora.org>
> wrote:
>>
>> For a given byte clock, if VCO recalc value is exactly same as
>> vco set rate value, vco_set_rate does not get called assuming
>> VCO is already set to required value. But Due to GDSC toggle,
>> VCO values are erased in the HW. To make sure VCO is programmed
>> correctly, we forcefully call set_rate from vco_prepare.
>
> Is this specific to certain SoCs? I don't think I've observed this.

As far as Qualcomm SOCs are concerned, since pll is analog and the value
is directly read from hardware if we get recalc value same as set rate
value, the vco_set_rate will not be invoked. We checked in our idp
device which has the same SOC but it works there since the rates are
different.