linux-kernel - Re: [PATCH v1] clk: qcom: gcc-sc8280xp: add cxo as parent for gcc_ufs_ref_clkref

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Date:   Wed, 2 Nov 2022 14:15:26 +0530
From:   Shazad Hussain <quic_shazhuss@...cinc.com>
To:     Johan Hovold <johan@...nel.org>
CC:     Stephen Boyd <sboyd@...nel.org>, <andersson@...nel.org>,
        <bmasney@...hat.com>, Andy Gross <agross@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Michael Turquette <mturquette@...libre.com>,
        <linux-arm-msm@...r.kernel.org>, <linux-clk@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1] clk: qcom: gcc-sc8280xp: add cxo as parent for
 gcc_ufs_ref_clkref_clk



On 11/2/2022 1:43 PM, Johan Hovold wrote:
> On Wed, Nov 02, 2022 at 01:28:48PM +0530, Shazad Hussain wrote:
>> On 11/2/2022 12:46 PM, Johan Hovold wrote:
>>> On Tue, Nov 01, 2022 at 11:23:59AM -0700, Stephen Boyd wrote:
>>>> Quoting Shazad Hussain (2022-10-30 07:23:33)
>>>>> Since 'commit f3aa975e230e ("arm64: dts: qcom: sc8280xp: correct ref
>>>>
>>>> So we should have a Fixes tag for this commit? Or really back to the
>>>> beginning of the driver?
>>>>
>>>>> clock for ufs_mem_phy")' we need to explicitly make cxo as parent to
>>>>> gcc_ufs_ref_clkref_clk to have an independent vote from ufs_mem_phy.
>>>
>>> The commit message is slightly misleading as this affects the other UFS
>>> PHY as well.
>>>
>>> If CX is indeed a parent of this clock then the issue has been there
>>> since the clock driver was added. (And otherwise, the PHY binding may
>>> need to be amended instead.)
> 
>> CX is not the actual parent of this clk. GCC_UFS_REF_CLKREF_CLK is an
>> external clk to the device, which needs to be voted. If we use the
>> GCC_UFS_REF_CLKREF_CLK as ref clk, we don't have explicit vote for CX
>> from ufs_mem_phy.
>>
>> If no client votes for CX,(very unlikely) then it's won't be ON for
>> ufs_mem_phy as well right ! So to maintain the voting to CX, we make
>> this as parent to ref clk.
> 
> Right, but if the PHYs really requires CX and it is not an ancestor of
> the refclk then this should be described by the binding (and not be
> hidden away in the clock driver).
> 
> Johan

This makes sense, will be posting v2 post for the same.
I assume this should use the Fixes tag then !

Shazad