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

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Message-ID: <CAOCk7Nr9n-xLtWq=LEM-QFhJcY+QOuzazsoi-yjErA9od2Jwmw@mail.gmail.com>
Date:   Thu, 6 Feb 2020 07:59:52 -0700
From:   Jeffrey Hugo <jeffrey.l.hugo@...il.com>
To:     Harigovindan P <harigovi@...eaurora.org>
Cc:     "open list:DRM PANEL DRIVERS" <dri-devel@...ts.freedesktop.org>,
        MSM <linux-arm-msm@...r.kernel.org>,
        freedreno <freedreno@...ts.freedesktop.org>,
        DTML <devicetree@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Rob Clark <robdclark@...il.com>, nganji@...eaurora.org,
        Sean Paul <seanpaul@...omium.org>, kalyan_t@...eaurora.org,
        "Kristian H. Kristensen" <hoegsberg@...omium.org>
Subject: Re: [Freedreno] [v1] drm/msm/dsi/pll: call vco set rate explicitly

On Thu, Feb 6, 2020 at 2:13 AM Harigovindan P <harigovi@...eaurora.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.