linux-kernel - Re: [PATCH 5/8] clk: qcom: support for duplicate freq in RCG2 freq table

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Date: Tue, 23 Jan 2024 00:35:22 +0800
From: Ziyang Huang <hzyitc@...look.com>
To: Andrew Lunn <andrew@...n.ch>
Cc: mcoquelin.stm32@...il.com, alexandre.torgue@...s.st.com,
 richardcochran@...il.com, p.zabel@...gutronix.de, matthias.bgg@...il.com,
 angelogioacchino.delregno@...labora.com, linux-kernel@...r.kernel.org,
 linux-stm32@...md-mailman.stormreply.com,
 linux-arm-kernel@...ts.infradead.org, netdev@...r.kernel.org,
 linux-mediatek@...ts.infradead.org, Praveenkumar I <ipkumar@...eaurora.org>,
 Abhishek Sahu <absahu@...eaurora.org>
Subject: Re: [PATCH 5/8] clk: qcom: support for duplicate freq in RCG2 freq
 table

在 2024/1/22 0:57, Andrew Lunn 写道:
> On Sun, Jan 21, 2024 at 08:42:34PM +0800, Ziyang Huang wrote:
>> From: Praveenkumar I <ipkumar@...eaurora.org>
>>
>> Currently RCG code looks up the frequency table during set
>> rate and return the first available frequency greater than
>> requested rate. If CLK_SET_RATE_PARENT flag is set then the
>> set_rate request will go to its parent otherwise the clock
>> framework will configure pre-div, m and n according to the
>> returned frequency table entry. In this case, it is assuming
>> that parent clock will run in the same frequency with which
>> pre-div, m and n has been derived. But it may be possible
>> that the parent clock supports multiple frequency and the
>> same frequency can be derived with different pre-div, m and
>> n values depending upon current frequency.  Also, the same
>> frequency can be derived from different parent sources and
>> currently there is no option for having duplicate
>> frequencies in frequency table and choosing the best one
>> according to current rate.
>>
>> Now this patch adds the support for having duplicate
>> frequencies in frequency table. During set rate, it will
>> compare the actual rate for each entry with requested rate
>> and will select the best entry in which the difference will
>> be less.
>>
>> The existing functionality won’t be affected with this code
>> change since this code change will hit only if frequency
>> table has duplicate values.
> 
> A good commit message for a change!
> 
>>
>> Change-Id: I97d9e1b55d8f3ee095f6f01729af527ba90e50e5
>> Signed-off-by: Abhishek Sahu <absahu@...eaurora.org>
>> (cherry picked from commit 775e7d3b69ffc97afb5bd5a6c9c423f2f4d8a0b2)
>> Signed-off-by: Praveenkumar I <ipkumar@...eaurora.org>
>>
>> Change-Id: If10193fc79a3c1375ab73597813745ff1f4df0ad
>>
>> Pick from https://git.codelinaro.org/clo/qsdk/oss/kernel/linux-ipq-5.4/-/commit/6dfb368bae130bee58e00ddf8330b55066e1c8c5
>>
>> Signed-off-by: Ziyang Huang <hzyitc@...look.com>
> 
> Please clean up these tags. These Change-ID tags are meaningless in
> mainline. 775e7d3b69ffc97afb5bd5a6c9c423f2f4d8a0b2 is not in mainline
> either. The picked from might be interesting, but please put it into
> the body of the commit message, not mixed in with the tags.
> 
> Who actually wrote this patch? The first Signed-off-by: is from
> Abhishek Sahu. But you have a From of Praveenkumar I ?

I have no idea about this. This patch is from Qualcomm vendor linux 
code. And it's necessary for choosing parent and calculating clock rate 
correctly.

What's more, I don't known how to deal with these commit message since 
I'm not the author and I'm not sure do I have right to edit them even 
though this is GPL code.

> 
>      Andrew
> 
> ---
> pw-bot: cr