linux-kernel - Re: [PATCH 1/9] clk: qcom: gcc-msm8998: Wire up gcc_mmss

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Message-ID: <d25b0510-4f80-c46a-aa53-f940b44c9392@somainline.org>
Date:   Thu, 14 Jan 2021 23:49:22 +0100
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...ainline.org>
To:     Jeffrey Hugo <jeffrey.l.hugo@...il.com>
Cc:     MSM <linux-arm-msm@...r.kernel.org>, konrad.dybcio@...ainline.org,
        marijn.suijten@...ainline.org, martin.botka@...ainline.org,
        phone-devel@...r.kernel.org, lkml <linux-kernel@...r.kernel.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Rob Herring <robh+dt@...nel.org>, linux-clk@...r.kernel.org,
        DTML <devicetree@...r.kernel.org>
Subject: Re: [PATCH 1/9] clk: qcom: gcc-msm8998: Wire up gcc_mmss_gpll0 clock

Il 14/01/21 23:44, Jeffrey Hugo ha scritto:
> On Thu, Jan 14, 2021 at 3:40 PM AngeloGioacchino Del Regno
> <angelogioacchino.delregno@...ainline.org> wrote:
>>
>> Il 14/01/21 23:33, Jeffrey Hugo ha scritto:
>>> On Thu, Jan 14, 2021 at 3:13 PM AngeloGioacchino Del Regno
>>> <angelogioacchino.delregno@...ainline.org> wrote:
>>>>
>>>> Il 14/01/21 23:12, Jeffrey Hugo ha scritto:
>>>>> On Sat, Jan 9, 2021 at 6:47 AM AngeloGioacchino Del Regno
>>>>> <angelogioacchino.delregno@...ainline.org> wrote:
>>>>>>
>>>>>> This clock enables the GPLL0 output to the multimedia subsystem
>>>>>> clock controller.
>>>>>>
>>>>>> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...ainline.org>
>>>>>
>>>>> Any reason why you are not also adding the div_clk?
>>>>>
>>>>
>>>> Yes, just one: I haven't tested it... and my devices worked without.
>>>> Perhaps we can add it whenever we find out if something really needs it?
>>>
>>> I'm mildly surprised you need to turn on the gate to the PLL0 out, but
>>> not the div_out.  The div_out/div_clk is also fed into every RCG that
>>> exists in the MMCC.
>>>
>>> Per the frequency plan the following RCGs require it -
>>>
>>> cci
>>> cpp
>>> fd_core
>>> camss_gp[0-1]
>>> jpeg0
>>> mclk[0-3]
>>> csi[0-2]phytimer
>>> dp_gtc
>>> maxi
>>> axi
>>> ahb
>>>
>>> Also, I'm very interested in all things 8998, and would generally
>>> appreciate being added to the to: list.
>>>
>>
>> To be honest, I was surprised as well because.. yes, I know that these
>> RCGs seem to need it, but then their clock tables don't contain any
>> reference to the gpll0 divider, hence it's never getting used - and that
>> works great, for now.
>>
>> I am aware of the fact that the clocks that you've mentioned are using
>> the divider to reduce jitter, but I haven't done any camera test on my
>> devices yet: that's definitely in my plans and I really can't wait to do
>> that (as I successfully did for SDM630/660), but... we have more than
>> 100 patches in our trees.
>> We need to get upstream in the same working order as what we have here,
>> so that we don't diverge that much and our work is kept in a
>> maintainable state (avoiding to lose pieces around).
>>
>> I'm sure that I'll send a commit adding the gpll0 divider branch as soon
>> as I will start the camera work: I feel it, it's going to give me issues
>> without, in that field.
>>
>> By the way, noted. I'll make sure to add you in the to/cc for all of the
>> next series regarding 8998 that I'll send.
>>
>> Meanwhile, you may want to check out all the recent patches that I've
>> sent, as like 90% are MSM8998-centric... :))
> 
> I noticed, and I'm excited to see additional work since I've had a
> lack of spare time, although I think you've monopolized my backlog  :)
> 

I just... had some time... and passion about it :)))

P.S.: I'm not done yet!! :)