linux-kernel - Re: [PATCH v9 6/6] arm64: dts: qcom: ipq9574: Add icc provider ability to gcc

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Date: Wed, 12 Jun 2024 15:52:51 +0300
From: Georgi Djakov <djakov@...nel.org>
To: Varadarajan Narayanan <quic_varada@...cinc.com>
Cc: Konrad Dybcio <konrad.dybcio@...aro.org>,
 Dmitry Baryshkov <dmitry.baryshkov@...aro.org>, andersson@...nel.org,
 mturquette@...libre.com, sboyd@...nel.org, robh@...nel.org,
 krzk+dt@...nel.org, conor+dt@...nel.org, quic_anusha@...cinc.com,
 linux-arm-msm@...r.kernel.org, linux-clk@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-pm@...r.kernel.org
Subject: Re: [PATCH v9 6/6] arm64: dts: qcom: ipq9574: Add icc provider
 ability to gcc

On 12.06.24 13:28, Varadarajan Narayanan wrote:
> On Wed, Jun 12, 2024 at 11:48:17AM +0300, Georgi Djakov wrote:
>> On 12.06.24 9:30, Varadarajan Narayanan wrote:
>>> On Tue, Jun 11, 2024 at 02:29:48PM +0300, Georgi Djakov wrote:
>>>> On 11.06.24 12:42, Varadarajan Narayanan wrote:
>>>>> On Thu, Jun 06, 2024 at 04:06:01PM +0200, Konrad Dybcio wrote:
>>>>>> On 8.05.2024 10:10 AM, Dmitry Baryshkov wrote:
>>>>>>> On Wed, 8 May 2024 at 09:53, Varadarajan Narayanan
>>>>>>> <quic_varada@...cinc.com> wrote:
>>>>>>>>
>>>>>>>> On Fri, May 03, 2024 at 04:51:04PM +0300, Georgi Djakov wrote:
>>>>>>>>> Hi Varada,
>>>>>>>>>
>>>>>>>>> Thank you for your work on this!
>>>>>>>>>
>>>>>>>>> On 2.05.24 12:30, Varadarajan Narayanan wrote:
>>>>>>>>>> On Tue, Apr 30, 2024 at 12:05:29PM +0200, Konrad Dybcio wrote:
>>>>>>>>>>> On 25.04.2024 12:26 PM, Varadarajan Narayanan wrote:
>>>>>>>>>>>> On Tue, Apr 23, 2024 at 02:58:41PM +0200, Konrad Dybcio wrote:
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>> On 4/18/24 11:23, Varadarajan Narayanan wrote:
>>>>>>>>>>>>>> IPQ SoCs dont involve RPM in managing NoC related clocks and
>>>>>>>>>>>>>> there is no NoC scaling. Linux itself handles these clocks.
>>>>>>>>>>>>>> However, these should not be exposed as just clocks and align
>>>>>>>>>>>>>> with other Qualcomm SoCs that handle these clocks from a
>>>>>>>>>>>>>> interconnect provider.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Hence include icc provider capability to the gcc node so that
>>>>>>>>>>>>>> peripherals can use the interconnect facility to enable these
>>>>>>>>>>>>>> clocks.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
>>>>>>>>>>>>>> Signed-off-by: Varadarajan Narayanan <quic_varada@...cinc.com>
>>>>>>>>>>>>>> ---
>>>>>>>>>>>>>
>>>>>>>>>>>>> If this is all you do to enable interconnect (which is not the case,
>>>>>>>>>>>>> as this patch only satisfies the bindings checker, the meaningful
>>>>>>>>>>>>> change happens in the previous patch) and nothing explodes, this is
>>>>>>>>>>>>> an apparent sign of your driver doing nothing.
>>>>>>>>>>>>
>>>>>>>>>>>> It appears to do nothing because, we are just enabling the clock
>>>>>>>>>>>> provider to also act as interconnect provider. Only when the
>>>>>>>>>>>> consumers are enabled with interconnect usage, this will create
>>>>>>>>>>>> paths and turn on the relevant NOC clocks.
>>>>>>>>>>>
>>>>>>>>>>> No, with sync_state it actually does "something" (sets the interconnect
>>>>>>>>>>> path bandwidths to zero). And *this* patch does nothing functionally,
>>>>>>>>>>> it only makes the dt checker happy.
>>>>>>>>>>

[..]

> 
> nsscc_ipq9574 was not using icc_sync_state. After adding that, I
> can see the following messages printed from icc_sync_state. I
> also added a print to confirm if 'p->set(n, n);' is called.

Ok, that's good! So now when all providers are using sync_state, we
can go back to the initial comment from Konrad. I think you should
re-check the tests that you did, as the current results just lead to
more questions than answers. Maybe it was just the sync-state that
was missing, or there is some other issue.

BR,
Georgi

[..]
> 
> The gcc based interconnect paths are referenced by PCIe controller
> nodes. Please refer to this patch
> 
> 	[PATCH V5 4/6] arm64: dts: qcom: ipq9574: Add PCIe PHYs and controller nodes
> 	https://lore.kernel.org/linux-arm-msm/20240512082858.1806694-5-quic_devipriy@quicinc.com/
> 
> Sorry, did not post the nsscc related patches since this base ICC
> patch hasn't reached closure. The nsscc patches are very similar
> to this gcc based series. Wanted to gather the issues raised in
> this and address them in nsscc so that it is in a more acceptable
> shape.
> 
> Thanks
> Varada