linux-kernel - Re: [PATCH v3 3/3] clk: qcom: Add Global Clock controller (GCC) driver for SDM845

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Date:   Wed, 18 Apr 2018 22:08:41 +0530
From:   Manu Gautam <mgautam@...eaurora.org>
To:     Amit Nischal <anischal@...eaurora.org>,
        Stephen Boyd <sboyd@...nel.org>
Cc:     Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Andy Gross <andy.gross@...aro.org>,
        David Brown <david.brown@...aro.org>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        Odelu Kukatla <okukatla@...eaurora.org>,
        Taniya Das <tdas@...eaurora.org>,
        linux-arm-msm@...r.kernel.org, linux-soc@...r.kernel.org,
        linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org,
        Doug Anderson <dianders@...omium.org>
Subject: Re: [PATCH v3 3/3] clk: qcom: Add Global Clock controller (GCC)
 driver for SDM845

Hi Amit,


On 4/18/2018 6:33 PM, Amit Nischal wrote:
>>> +       /* Disable the GPLL0 active input to MMSS and GPU via MISC registers */
>>> +       regmap_update_bits(regmap, 0x09ffc, 0x3, 0x3);
>>> +       regmap_update_bits(regmap, 0x71028, 0x3, 0x3);
>>
>> I think we'll have to throw in the pipe clk branch stuff in here too?
>> And then drop the pipe clks from the driver?
>
> All the USB pipe clocks would be taken care. The PCIE pipe branch
> clocks would have to be explicitly disabled so as to retain the
> memory logic. Otherwise, it would lead to memory corruption in case
> the external source is directly disabled without disabling the branch clock. 

PHY driver is same for both USB and PCIE and both PHYs use pipe_clk.
If there is indeed some limitation and pipe_clk cant be left enabled
always then I will suggest to not change pipe_clk handling for USB as well.

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