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Date: Tue, 5 Mar 2024 16:23:21 +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 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
>> @@ -240,6 +240,7 @@ struct qcom_pcie {
>> struct phy *phy;
>> struct gpio_desc *reset;
>> struct icc_path *icc_mem;
>> + struct icc_path *icc_cpu;
>> const struct qcom_pcie_cfg *cfg;
>> struct dentry *debugfs;
>> bool suspended;
>> @@ -1372,6 +1373,9 @@ static int qcom_pcie_icc_init(struct qcom_pcie *pcie)
>> if (IS_ERR(pcie->icc_mem))
>> return PTR_ERR(pcie->icc_mem);
>>
>> + pcie->icc_cpu = devm_of_icc_get(pci->dev, "cpu-pcie");
>> + if (IS_ERR(pcie->icc_cpu))
>> + return PTR_ERR(pcie->icc_cpu);
>> /*
>> * Some Qualcomm platforms require interconnect bandwidth constraints
>> * to be set before enabling interconnect clocks.
>> @@ -1381,7 +1385,19 @@ static int qcom_pcie_icc_init(struct qcom_pcie *pcie)
>> */
>> ret = icc_set_bw(pcie->icc_mem, 0, QCOM_PCIE_LINK_SPEED_TO_BW(1));
>> if (ret) {
>> - dev_err(pci->dev, "failed to set interconnect bandwidth: %d\n",
>> + dev_err(pci->dev, "failed to set interconnect bandwidth for pcie-mem: %d\n",
>
> "PCIe-MEM"
>
>> + ret);
>> + return ret;
>> + }
>> +
>> + /*
>> + * The config space, BAR space and registers goes through cpu-pcie path
>> + * Set peak bandwidth to 1KBps as recommended by HW team for this path
>> + * all the time.
>
> How about,
>
> "Since the CPU-PCIe path is only used for activities like register
> access, Config/BAR space access, HW team has recommended to use a
> minimal bandwidth of 1KBps just to keep the link active."
>
>> + */
>> + ret = icc_set_bw(pcie->icc_cpu, 0, kBps_to_icc(1));
>> + if (ret) {
>> + dev_err(pci->dev, "failed to set interconnect bandwidth for cpu-pcie: %d\n",
>> ret);
>> return ret;
>> }
>> @@ -1573,7 +1589,7 @@ static int qcom_pcie_suspend_noirq(struct device *dev)
>> */
>> ret = icc_set_bw(pcie->icc_mem, 0, kBps_to_icc(1));
>> if (ret) {
>> - dev_err(dev, "Failed to set interconnect bandwidth: %d\n", ret);
>> + dev_err(dev, "Failed to set interconnect bandwidth for pcie-mem: %d\n", ret);
>
> "PCIe-MEM"
>
>> return ret;
>> }
>>
>> @@ -1597,6 +1613,18 @@ static int qcom_pcie_suspend_noirq(struct device *dev)
>> pcie->suspended = true;
>> }
>>
>> + /* Remove CPU path vote after all the register access is done */
>
> "Remove the vote for CPU-PCIe path now, since at this point onwards, no register
> access will be done."
>
>> + 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.
- Krishna Chaitanya.
>> + pcie->suspended = false;
>> + }
>> + qcom_pcie_icc_update(pcie);
>> + return ret;
>> + }
>> +
>> return 0;
>> }
>>
>> @@ -1605,6 +1633,12 @@ static int qcom_pcie_resume_noirq(struct device *dev)
>> struct qcom_pcie *pcie = dev_get_drvdata(dev);
>> int ret;
>>
>> + ret = icc_enable(pcie->icc_cpu);
>> + if (ret) {
>> + dev_err(dev, "failed to enable icc path of cpu-pcie: %d\n", ret);
>
> "CPU-PCIe"
>
> - Mani
>
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