Re: [PATCH v14 1/4] PCI: qcom: Add ICC bandwidth vote for CPU to PCIe path

[Manivannan Sadhasivam]

On Fri, Jun 14, 2024 at 03:14:10PM +0300, Ilpo Järvinen wrote:
> On Sun, 9 Jun 2024, Krishna chaitanya chundru wrote:
> 
> > To access the host controller registers of the host controller and the
> > endpoint BAR/config space, the CPU-PCIe ICC (interconnect) path should
> > be voted otherwise it may lead to NoC (Network on chip) timeout.
> > We are surviving because of other driver voting 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 which is sufficient enough
> > to keep the path active and is recommended by HW team.
> > 
> > During S2RAM (Suspend-to-RAM), the DBI access can happen very late (while
> > disabling the boot CPU). So do not disable the CPU-PCIe interconnect path
> > during S2RAM as that may lead to NoC error.
> > 
> > Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@xxxxxxxxxx>
> > Signed-off-by: Krishna chaitanya chundru <quic_krichai@xxxxxxxxxxx>
> > Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx>
> > ---
> >  drivers/pci/controller/dwc/pcie-qcom.c | 45 +++++++++++++++++++++++++++++++---
> >  1 file changed, 41 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> > index 5f9f0ff19baa..ff1d891c8b9a 100644
> > --- a/drivers/pci/controller/dwc/pcie-qcom.c
> > +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> > @@ -253,6 +253,7 @@ 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;
> > @@ -1369,6 +1370,9 @@ 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.
> > @@ -1378,11 +1382,25 @@ 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 bandwidth for PCIe-MEM interconnect path: %d\n",
> >  			ret);
> 
> I think it would be better to separate these message clarifications into a 
> separate patch. It would make both patches more into the point.
> 

No, it doesn't make sense. This patch introduces ICC vote for CPU-PCIe path, so
it _should_ also update the error message.

- Mani

> Other than that, the change looked okay to me.
> 
> -- 
>  i.
> 
> >  		return ret;
> >  	}
> >  
> > +	/*
> > +	 * Since the CPU-PCIe path is only used for activities like register
> > +	 * access of the host controller and endpoint Config/BAR space access,
> > +	 * HW team has recommended to use a minimal bandwidth of 1KBps just to
> > +	 * keep the path active.
> > +	 */
> > +	ret = icc_set_bw(pcie->icc_cpu, 0, kBps_to_icc(1));
> > +	if (ret) {
> > +		dev_err(pci->dev, "Failed to set bandwidth for CPU-PCIe interconnect path: %d\n",
> > +			ret);
> > +		icc_set_bw(pcie->icc_mem, 0, 0);
> > +		return ret;
> > +	}
> > +
> >  	return 0;
> >  }
> >  
> > @@ -1408,7 +1426,7 @@ static void qcom_pcie_icc_update(struct qcom_pcie *pcie)
> >  
> >  	ret = icc_set_bw(pcie->icc_mem, 0, width * QCOM_PCIE_LINK_SPEED_TO_BW(speed));
> >  	if (ret) {
> > -		dev_err(pci->dev, "failed to set interconnect bandwidth: %d\n",
> > +		dev_err(pci->dev, "Failed to set bandwidth for PCIe-MEM interconnect path: %d\n",
> >  			ret);
> >  	}
> >  }
> > @@ -1570,7 +1588,7 @@ 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 bandwidth for PCIe-MEM interconnect path: %d\n", ret);
> >  		return ret;
> >  	}
> >  
> > @@ -1594,7 +1612,18 @@ static int qcom_pcie_suspend_noirq(struct device *dev)
> >  		pcie->suspended = true;
> >  	}
> >  
> > -	return 0;
> > +	/*
> > +	 * Only disable CPU-PCIe interconnect path if the suspend is non-S2RAM.
> > +	 * Because on some platforms, DBI access can happen very late during the
> > +	 * S2RAM and a non-active CPU-PCIe interconnect path may lead to NoC
> > +	 * error.
> > +	 */
> > +	if (pm_suspend_target_state != PM_SUSPEND_MEM) {
> > +		ret = icc_disable(pcie->icc_cpu);
> > +		if (ret)
> > +			dev_err(dev, "Failed to disable CPU-PCIe interconnect path: %d\n", ret);
> > +	}
> > +	return ret;
> >  }
> >  
> >  static int qcom_pcie_resume_noirq(struct device *dev)
> > @@ -1602,6 +1631,14 @@ static int qcom_pcie_resume_noirq(struct device *dev)
> >  	struct qcom_pcie *pcie = dev_get_drvdata(dev);
> >  	int ret;
> >  
> > +	if (pm_suspend_target_state != PM_SUSPEND_MEM) {
> > +		ret = icc_enable(pcie->icc_cpu);
> > +		if (ret) {
> > +			dev_err(dev, "Failed to enable CPU-PCIe interconnect path: %d\n", ret);
> > +			return ret;
> > +		}
> > +	}
> > +
> >  	if (pcie->suspended) {
> >  		ret = qcom_pcie_host_init(&pcie->pci->pp);
> >  		if (ret)
> > 
> > 

-- 
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