linux-kernel - Re: [PATCH v8] clk: qcom: Add lpass clock controller driver for SDM845

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Date:   Sat, 3 Nov 2018 08:46:20 +0530
From:   Taniya Das <tdas@...eaurora.org>
To:     Stephen Boyd <sboyd@...nel.org>,
        Michael Turquette <mturquette@...libre.com>
Cc:     Andy Gross <andy.gross@...aro.org>,
        David Brown <david.brown@...aro.org>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        linux-arm-msm@...r.kernel.org, linux-soc@...r.kernel.org,
        linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org,
        Bjorn Andersson <bjorn.andersson@...aro.org>
Subject: Re: [PATCH v8] clk: qcom: Add lpass clock controller driver for
 SDM845

Hello Stephen,

On 11/2/2018 10:08 PM, Stephen Boyd wrote:
> Quoting Taniya Das (2018-10-28 00:35:40)
>> Add support for the lpass clock controller found on SDM845 based devices.
>> This would allow lpass peripheral loader drivers to control the clocks to
>> bring the subsystem out of reset.
>> LPASS clocks present on the global clock controller would be registered
>> with the clock framework based on the device tree flag. Also do not gate
>> these clocks if they are left unused, as the lpass clocks require the
>> global clock controller lpass clocks to be enabled before they are
>> accessed. Mark the GCC lpass clocks as CRITICAL, for the LPASS clock
>> access.
> 
> Thanks for the useful commit text!
> 
>>
>> diff --git a/drivers/clk/qcom/gcc-sdm845.c b/drivers/clk/qcom/gcc-sdm845.c
>> index 08d593e..9d60474 100644
>> --- a/drivers/clk/qcom/gcc-sdm845.c
>> +++ b/drivers/clk/qcom/gcc-sdm845.c
>> @@ -3583,6 +3613,13 @@ static int gcc_sdm845_probe(struct platform_device *pdev)
>>          if (ret)
>>                  return ret;
>>
>> +       if (!of_property_read_bool(pdev->dev.of_node, "qcom,lpass-protected")) {
> 
> Bjorn told me over IRC that the QSPI clks are also protected on MTP and
> can't be read. So we're now causing MTP to fail on linus' tree. I think
> we need to add a generic property to the GCC node to indicate what clks
> are protected and shouldn't be touched by the OS. The function would go
> and knock out any protected clks by replacing their pointers with NULL.
> The property would be:
> 
>     protected-clocks = <clock-specifier-list>;
> 
> So for this node it would look like:
> 
>     gcc: clock-controller@...0 {
>          reg = <0xf00 0xbaf>;
> 
>          protected-clocks = <&gcc GCC_LPASS_Q6_AXI_CLK>,
>                             <&gcc GCC_LPASS_SWAY_CLK>,
>                             <&gcc GCC_QSPI_CORE_CLK_SRC>,
>                             etc.
>     };
> 
> Sorry for derailing this patch series so late in the process. This patch
> will need to be updated to work with that new DT property instead of
> having a custom qcom property. Otherwise the patch looks good and I
> think we're ready to merge it when the merge window closes and I can
> rewind clk-next.
> 

How about moving the QSPI clocks too under this qcom property? Later 
could add the support?

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