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

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Date: Fri, 28 Jun 2024 14:18:06 +0530
From: Varadarajan Narayanan <quic_varada@...cinc.com>
To: Konrad Dybcio <konrad.dybcio@...aro.org>
CC: Georgi Djakov <djakov@...nel.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 Thu, Jun 27, 2024 at 12:00:35AM +0200, Konrad Dybcio wrote:
> On 19.06.2024 9:36 AM, Varadarajan Narayanan wrote:
>
> [...]
>
>
> > Tested the patches with both gcc and nsscc providers having
> > 'sync_state' set to icc_sync_state.
> >
> > 	# dmesg | grep synced
> > 	[    3.029820] qcom,gcc-ipq9574 1800000.clock-controller: interconnect provider is in synced state
> > 	[    3.470106] qcom,nsscc-ipq9574 39b00000.clock-controller: interconnect provider is in synced state
> >
> > I can see that icc_sync_state is getting called and clocks
> > related to paths with zero bandwidth are getting disabled.
> >
> > Will post the NSSCC patches to get the full picture.
>
> Going back to the original question, does removing interconnects = from
> things like PCIe now make them not work / crash the device, which would
> indicate the NoC clocks were indeed gated?

Yes. With and without 'interconnects =', the following behaviour
is same
	* Boot completes
	* PCIe devices were probed succesfully and can be
	  seen in /proc/bus/pci/devices.
	* icc_sync_state is called. The system has 4 pcie nodes
	  in the DT, out of which pcie0 is not enabled.

The difference is seen in icc_sync_state

    With 'interconnects ='

	* During icc_sync_state, the following 2 clocks
	  corresponding to the interconnects of 'pcie0' get
	  disabled.

	[    2.986356] ---> clk_core_disable_lock: gcc_anoc_pcie0_1lane_m_clk
	[    3.012486] ---> clk_core_disable_lock: gcc_snoc_pcie0_1lane_s_clk

	* System shutdown also completes without issues

    Without the 'interconnects =',

	* During icc_sync_state, the following clocks
	  corresponding to the interconnects of all the 4 PCIe
	  nodes get disabled.

	[    2.887860] ---> clk_core_disable_lock: gcc_anoc_pcie0_1lane_m_clk
	[    2.913988] ---> clk_core_disable_lock: gcc_snoc_pcie0_1lane_s_clk
	[    2.939857] ---> clk_core_disable_lock: gcc_anoc_pcie1_1lane_m_clk
	[    2.965725] ---> clk_core_disable_lock: gcc_snoc_pcie1_1lane_s_clk
	[    2.991594] ---> clk_core_disable_lock: gcc_anoc_pcie2_2lane_m_clk
	[    3.017463] ---> clk_core_disable_lock: gcc_snoc_pcie2_2lane_s_clk
	[    3.043328] ---> clk_core_disable_lock: gcc_anoc_pcie3_2lane_m_clk
	[    3.069201] ---> clk_core_disable_lock: gcc_snoc_pcie3_2lane_s_clk

	* System shutdown hangs (possibly due to un-clocked
	  access of PCIe register) in pcie_pme_interrupt_enable

		[   10.773134]  dump_stack+0x18/0x24
		[   10.776779]  pcie_pme_remove+0x2c/0x88
		[   10.780078]  pcie_port_remove_service+0x50/0x74
		[   10.783725]  device_remove+0x12c/0x148
		[   10.788151]  __device_release_driver+0x65c/0x8cc
		[   10.791972]  device_release_driver+0x2c/0x44
		[   10.796746]  bus_remove_device+0xcc/0x10c
		[   10.800999]  device_del+0x14c/0x400
		[   10.804904]  device_unregister+0x18/0x34
		[   10.808203]  remove_iter+0x2c/0x3c
		[   10.812369]  device_for_each_child+0x60/0xb4
		[   10.815583]  pcie_portdrv_shutdown+0x34/0x90
		[   10.820009]  pci_device_shutdown+0x34/0x74
		[   10.824263]  device_shutdown+0x150/0x258
		[   10.828169]  kernel_restart_prepare+0x98/0xbc
		[   10.832249]  kernel_restart+0x44/0x110
		[   10.836502]  __do_sys_reboot+0x18c/0x304

I believe, this is confirms NOC clocks getting disabled by
icc_sync_state.

Thanks
Varada