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

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Date: Fri, 05 Apr 2024 14:32:10 -0700
From: Stephen Boyd <sboyd@...nel.org>
To: Abhishek Sahu <absahu@...eaurora.org>, Bjorn Andersson <andersson@...nel.org>, Bryan O'Donoghue <bryan.odonoghue@...aro.org>, Conor Dooley <conor+dt@...nel.org>, Konrad Dybcio <konrad.dybcio@...aro.org>, Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Michael Turquette <mturquette@...libre.com>, Rob Herring <robh@...nel.org>, Satya Priya Kakitapalli (Temp) <quic_skakitap@...cinc.com>
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

Quoting Satya Priya Kakitapalli (Temp) (2024-04-04 23:27:29)
> 
> On 3/2/2024 9:43 PM, Bryan O'Donoghue wrote:
> >
> > Alternatively switch on the always-on clocks before the really_probe() 
> > but then roll back in a probe_err: goto
> >
> > probe_err:
> >     remap_bits_update(regmap, 0xc1e4, BIT(0), 0);
> >     pm_runtime_put_sync(&pdev->dev);
> >
> > There may be corner cases where always-on has to happen before 
> > really_probe() I suppose but as a general pattern the above should be 
> > how we go.
> >
> 
> I have rechecked this and see that this clock is PoR ON (i.e BIT(0) is 
> set upon power ON) and it should be kept always ON as per HW 
> recommendation. So even if the probe fails we shouldn't be clearing it 
> against the hw recommendation. We are setting the bit here again to make 
> sure it is set when the driver probes.
> 

Yes, always on clks should always be on. We don't turn them off if the
driver fails to probe. We should probably print a warning or something
if the register write fails, but since this is mmio it won't fail, so
just make sure they're on and move on.