On Tue, Apr 30, 2024 at 12:05:29PM +0200, Konrad Dybcio wrote:

On 25.04.2024 12:26 PM, Varadarajan Narayanan wrote:

quoted

On Tue, Apr 23, 2024 at 02:58:41PM +0200, Konrad Dybcio wrote:

quoted

On 4/18/24 11:23, Varadarajan Narayanan wrote:

quoted

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 <redacted>
Signed-off-by: Varadarajan Narayanan <redacted>
---

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.

I understand.

quoted

This interconnect will be used by the PCIe and NSS blocks. When
those patches were posted earlier, they were put on hold until
interconnect driver is available.

Once this patch gets in, PCIe for example will make use of icc.
Please refer to https://lore.kernel.org/linux-arm-msm/20230519090219.15925-5-quic_devipriy@quicinc.com/ (local).

The 'pcieX' nodes will include the following entries.

	interconnects = <&gcc MASTER_ANOC_PCIE0 &gcc SLAVE_ANOC_PCIE0>,
			<&gcc MASTER_SNOC_PCIE0 &gcc SLAVE_SNOC_PCIE0>;
	interconnect-names = "pcie-mem", "cpu-pcie";

Okay. What about USB that's already enabled? And BIMC/MEMNOC?

For USB, the GCC_ANOC_USB_AXI_CLK is enabled as part of the iface
clock. Hence, interconnect is not specified there.

MEMNOC to System NOC interfaces seem to be enabled automatically.
Software doesn't have to turn on or program specific clocks.

quoted

quoted

The expected reaction to "enabling interconnect" without defining the
required paths for your hardware would be a crash-on-sync_state, as all
unused (from Linux's POV) resources ought to be shut down.

Because you lack sync_state, the interconnects silently retain the state
that they were left in (which is not deterministic), and that's precisely
what we want to avoid.

I tried to set 'sync_state' to icc_sync_state to be invoked and
didn't see any crash.

Have you confirmed that the registers are actually written to, and with
correct values?

I tried the following combinations:-

1. Top of tree linux-next + This patch set

	* icc_sync_state called
	* No crash or hang observed
	* From /sys/kernel/debug/clk/clk_summary can see the
	  relevant clocks are set to the expected rates (compared
	  with downstream kernel)

2. Top of tree linux-next + This patch set + PCIe enablement

	* icc_sync_state NOT called
	* No crash or hang observed
	* From /sys/kernel/debug/clk/clk_summary can see the
	  relevant clocks are set to the expected rates (compared
	  with downstream kernel)

Does this answer your question? Please let me know if you were
looking for some other information.

Thanks
Varada