Devicetree

* Re: [PATCH 07/12] clk: qcom: gcc-mdm9607: Drop incorrect apss_tcu_clk_src
From: Stephan Gerhold @ 2026-06-10 14:09 UTC (permalink / raw)
  To: Konrad Dybcio
  Cc: Bjorn Andersson, Michael Turquette, Stephen Boyd, Georgi Djakov,
	Shawn Guo, Bryan O'Donoghue, Konrad Dybcio, Rob Herring,
	Krzysztof Kozlowski, Conor Dooley, Taniya Das, linux-arm-msm,
	linux-clk, linux-kernel, devicetree
In-Reply-To: <f55526ad-ecd2-47b2-8b8f-5aec429bc1c0@oss.qualcomm.com>

On Wed, Jun 10, 2026 at 03:50:11PM +0200, Konrad Dybcio wrote:
> On 6/9/26 4:14 PM, Stephan Gerhold wrote:
> > From: Stephan Gerhold <stephan@gerhold.net>
> > 
> > This clock does not seem to exist on MDM9607. Reading/writing the registers
> > always results in 0 or crashes. The math in the frequency table is also
> > broken. GPLL2 on MDM9607 runs at 480 MHz, so:
> > 
> >  - F(155000000, P_GPLL2, 6, 0, 0), // 480 MHz/6 = 80 MHz, not 155 MHz
> >  - F(310000000, P_GPLL2, 3, 0, 0), // 480 MHz/3 = 160 MHz, not 310 MHz
> > 
> > Presumably, this definition was mistakenly copied as-is from gcc-msm8916
> > (which uses 930 MHz for GPLL2). There are no branch consumers of this root
> > clock inside gcc-mdm9607 (notably, gcc_apss_tcu_clk has bimc_ddr_clk_src as
> > parent instead of this clock), so we can just drop it.
> > 
> > Cc: stable@vger.kernel.org
> > Fixes: 48b7253264ea ("clk: qcom: Add MDM9607 GCC driver")
> > Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
> > ---
> 
> It does, CMD_RCGR @ 0x37000
> 
> Interestingly, there's also an SMMU instance.. although downstream doesn't
> seem bothered with it
> 

Thanks for checking, but that still doesn't give us enough to work with
it. In particular:

 - What are the frequency tables? Which parents exist with which IDs?
 - What is the hid_width?
 - Where do we hook it up to some children?

The way it is right now it's definitely wrong. I don't think we'll need
it so removing it like this patch is probably the easiest thing to do...

Thanks,
Stephan

PS: This platform has the weird TZ-managed SMMU (like MSM8916), so there
isn't much you can do with it from Linux. Unless you are running TF-A,
then you can describe it as "arm,mmu-500" and use it for everything
pretty much exactly like you would normally expect. But you still don't
need to do anything with this clock.

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