linux-kernel - Re: [PATCH v8 3/7] PCI: qcom: Add ICC bandwidth vote for CPU to PCIe path

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Date: Fri, 5 Apr 2024 15:46:08 +0530
From: Krishna Chaitanya Chundru <quic_krichai@...cinc.com>
To: Manivannan Sadhasivam <mani@...nel.org>
CC: Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio
	<konrad.dybcio@...aro.org>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Rob Herring
	<robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
        Krzysztof Kozlowski
	<krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        Rob Herring
	<robh+dt@...nel.org>,
        Johan Hovold <johan+linaro@...nel.org>,
        Brian Masney
	<bmasney@...hat.com>, Georgi Djakov <djakov@...nel.org>,
        <linux-arm-msm@...r.kernel.org>, <linux-pci@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <vireshk@...nel.org>, <quic_vbadigan@...cinc.com>,
        <quic_skananth@...cinc.com>, <quic_nitegupt@...cinc.com>,
        <quic_parass@...cinc.com>,
        Bryan O'Donoghue <bryan.odonoghue@...aro.org>
Subject: Re: [PATCH v8 3/7] PCI: qcom: Add ICC bandwidth vote for CPU to PCIe
 path



On 4/5/2024 1:59 PM, Manivannan Sadhasivam wrote:
> On Tue, Mar 05, 2024 at 04:23:21PM +0530, Krishna Chaitanya Chundru wrote:
>>
>>
>> On 3/4/2024 11:11 PM, Manivannan Sadhasivam wrote:
>>> On Sat, Mar 02, 2024 at 09:29:57AM +0530, Krishna chaitanya chundru wrote:
>>>> To access PCIe registers, PCIe BAR space, config space the CPU-PCIe
>>>> ICC (interconnect consumers) path should be voted otherwise it may
>>>> lead to NoC (Network on chip) timeout. We are surviving because of
>>>> other driver vote for this path.
>>>>
>>>> As there is less access on this path compared to PCIe to mem path
>>>> add minimum vote i.e 1KBps bandwidth always.
>>>
>>> Please add the info that 1KBps is what shared by the HW team.
>>>
>> Ack to all the comments
>>>>
>>>> When suspending, disable this path after register space access
>>>> is done.
>>>>
>>>> Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
>>>> Signed-off-by: Krishna chaitanya chundru <quic_krichai@...cinc.com>
>>>> ---
>>>>    drivers/pci/controller/dwc/pcie-qcom.c | 38 ++++++++++++++++++++++++++++++++--
>>>>    1 file changed, 36 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
>>>> index 10f2d0bb86be..a0266bfe71f1 100644
>>>> --- a/drivers/pci/controller/dwc/pcie-qcom.c
>>>> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> 
> [...]
> 
>>>> +	ret = icc_disable(pcie->icc_cpu);
>>>> +	if (ret) {
>>>> +		dev_err(dev, "failed to disable icc path of cpu-pcie: %d\n", ret);
>>>
>>> "CPU-PCIe"
>>>
>>>> +		if (pcie->suspended) {
>>>> +			qcom_pcie_host_init(&pcie->pci->pp);
>>>
>>> Interesting. So if icc_disable() fails, can the IP continue to function?
>>>
>> As the ICC already enable before icc_disable() fails, the IP should work.
> 
> If icc_disable() fails, then most likely something is wrong with RPMh. How can
> the IP continue to work in that case?
>
Ok then I will log the error and return here

- Krishna Chaitanya.

> - Mani
>