linux-kernel - Re: [PATCH 4/5] clk: qcom: Add camera clock controller driver for SM8150

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Message-ID: <4817a5b0-5407-4437-b94a-fc8a1bfcd25d@linaro.org>
Date: Wed, 6 Mar 2024 13:55:45 +0000
From: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
To: "Satya Priya Kakitapalli (Temp)" <quic_skakitap@...cinc.com>,
 Bjorn Andersson <andersson@...nel.org>,
 Konrad Dybcio <konrad.dybcio@...aro.org>,
 Michael Turquette <mturquette@...libre.com>, Stephen Boyd
 <sboyd@...nel.org>, Abhishek Sahu <absahu@...eaurora.org>,
 Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
 Conor Dooley <conor+dt@...nel.org>
Cc: Stephen Boyd <sboyd@...eaurora.org>, linux-arm-msm@...r.kernel.org,
 linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org,
 devicetree@...r.kernel.org, Ajit Pandey <quic_ajipan@...cinc.com>,
 Imran Shaik <quic_imrashai@...cinc.com>, Taniya Das <quic_tdas@...cinc.com>,
 Jagadeesh Kona <quic_jkona@...cinc.com>
Subject: Re: [PATCH 4/5] clk: qcom: Add camera clock controller driver for
 SM8150

On 06/03/2024 08:30, Satya Priya Kakitapalli (Temp) wrote:
>>
>> Anyway I suspect the right thing to do is to define a 
>> titan_top_gdsc_clk with shared ops to "park" the GDSC clock to 19.2 
>> MHz instead of turning it off.
>>
>> You can get rid of the hard-coded always-on and indeed represent the 
>> clock in /sysfs - which is preferable IMO to just whacking registers 
>> to keep clocks always-on in probe anyway.
>>
>> Please try to define the titan_top_gdsc_clk as a shared_ops clock 
>> instead of hard coding to always on.
>>
> 
> Defining the gdsc clk allows consumers to control it, we do not want 
> this clock to be disabled/controlled from consumers. Hence it is better 
> to not model this clock and just keep it always on from probe.

Not if you mark it critical

static struct clk_branch cam_cc_gdsc_clk = {
         .halt_reg = 0xc1e4,
         .halt_check = BRANCH_HALT,
         .clkr = {
                 .enable_reg = 0xc1e4,
                 .enable_mask = BIT(0),
                 .hw.init = &(struct clk_init_data){
                         .name = "cam_cc_gdsc_clk",
                         .parent_hws = (const struct clk_hw*[]){
                                 &cam_cc_xo_clk_src.clkr.hw
                         },
                         .num_parents = 1,
                         .flags = CLK_IS_CRITICAL | CLK_SET_RATE_PARENT,
                         .ops = &clk_branch2_ops,
                 },
         },
};

and then add this to your camss clocks

<&clock_camcc CAM_CC_GDSC_CLK>;

The practice we have of just whacking clocks always-on in the probe() of 
the clock driver feels lazy to me, leaving the broken cleanups we have 
aside.

As a user of the system I'd rather see correct/complete data in 
/sys/kernel/debug/clk/clk_summary

Anyway I'm fine with setting the clock always on, I can always send out 
a series to address this bug-bear myself.

So yeah just fix the cleanup and then please feel free to add my

Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@...aro.org>