From: Jeffrey Hugo <jeffrey.l.hugo@gmail.com>
To: Harigovindan P <harigovi@codeaurora.org>
Cc: "open list:DRM PANEL DRIVERS" <dri-devel@lists.freedesktop.org>,
MSM <linux-arm-msm@vger.kernel.org>,
freedreno <freedreno@lists.freedesktop.org>,
DTML <devicetree@vger.kernel.org>,
lkml <linux-kernel@vger.kernel.org>,
Rob Clark <robdclark@gmail.com>,
nganji@codeaurora.org, Sean Paul <seanpaul@chromium.org>,
kalyan_t@codeaurora.org,
"Kristian H. Kristensen" <hoegsberg@chromium.org>
Subject: Re: [Freedreno] [v1] drm/msm/dsi/pll: call vco set rate explicitly
Date: Fri, 7 Feb 2020 07:10:55 -0700 [thread overview]
Message-ID: <CAOCk7NoCH9p9gOd7as=ty-EMeerAAhQtKZa8f2wZrDeV2LtGrw@mail.gmail.com> (raw)
In-Reply-To: <2f5abc857910f70faa119fea5bda81d7@codeaurora.org>
On Fri, Feb 7, 2020 at 5:38 AM <harigovi@codeaurora.org> wrote:
>
> 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.
This doesn't seem to be an answer to my question. What Qualcomm SoCs
does this issue apply to? Everything implementing the 10nm pll? One
specific SoC? I don't believe I've seen this on MSM8998, nor SDM845,
so I'm interested to know what is the actual impact here. I don't see
an "IDP" SoC in the IP catalog, so I really have no idea what you are
referring to.
next prev parent reply other threads:[~2020-02-07 14:11 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-06 9:12 [v1] drm/msm/dsi/pll: call vco set rate explicitly Harigovindan P
2020-02-06 14:59 ` [Freedreno] " Jeffrey Hugo
2020-02-07 12:38 ` harigovi
2020-02-07 14:10 ` Jeffrey Hugo [this message]
2020-02-11 5:58 ` harigovi
2020-02-11 15:44 ` Rob Clark
2020-02-11 15:59 ` Jeffrey Hugo
2020-02-12 0:28 ` Rob Clark
2020-02-12 4:05 ` Jeffrey Hugo
2020-02-12 5:10 ` Rob Clark
2020-02-17 10:42 ` harigovi
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