linux-kernel - Re: [PATCH v5 0/7] PM / devfreq: Use OPP interface to handle the frequency

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Message-ID: <CAOCOHw5+TtrCrnDUVj1QjBYb5tivsgTFL_8MgDGocAp0uWoEUw@mail.gmail.com>
Date:   Mon, 6 Nov 2017 10:11:13 -0800
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Chanwoo Choi <cw00.choi@...sung.com>
Cc:     MyungJoo Ham <myungjoo.ham@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        rafael.j.wysocki@...el.com, chanwoo@...nel.org,
        inki.dae@...sung.com, lkml <linux-kernel@...r.kernel.org>,
        Linux PM list <linux-pm@...r.kernel.org>,
        Vinayak Holikatti <vinholikatti@...il.com>,
        Vivek Gautam <vivek.gautam@...eaurora.org>
Subject: Re: [PATCH v5 0/7] PM / devfreq: Use OPP interface to handle the frequency

On Sun, Oct 22, 2017 at 6:32 PM, Chanwoo Choi <cw00.choi@...sung.com> wrote:
> These patches makes the devfreq to use the OPP interface and clean-up codes.
>

Hi Chanwoo,

This patch series breaks UFS support on modern Qualcomm platforms
(e.g. MSM8996).

Prior to this series the call to devm_devfreq_add_device() would
return ok even though the ufshcd device does not come with a opp
table. Afaict the code then relies on the devfreq code to target 0 and
MAX_INT (see ufshcd_devfreq_target()), to switch between a "high" and
"low" frequency.

I'm quite skeptical of the ufshcd code, so can you please confirm if
this usage of the devfreq interface is valid or not?

PS. If I do register some frequencies (and hack up
ufshcd_devfreq_target() accordingly) this works again, but the "high"
and "low" currently affects two clocks with different frequencies, so
I'm not sure how to properly describe the two clocks frequencies.
Should I just map "high"/"low" of the primary clock to "high"/"low"
frequencies of the secondary clock?

Regards,
Bjorn