PCI: qcom: Use OPP only if the platform supports it

With commit 5b6272e0 ("PCI: qcom: Add OPP support to scale
performance"), OPP was used to control the interconnect and power domains
if the platform supported OPP. Also to maintain the backward compatibility
with platforms not supporting OPP but just ICC, the above mentioned commit
assumed that if ICC was not available on the platform, it would resort to
OPP.

Unfortunately, some old platforms don't support either ICC or OPP. On those
platforms, resorting to OPP in the absence of ICC throws below errors from
OPP core during suspend and resume:

  qcom-pcie 1c08000.pcie: dev_pm_opp_set_opp: device opp doesn't exist
  qcom-pcie 1c08000.pcie: _find_key: OPP table not found (-19)

Also, it doesn't make sense to invoke the OPP APIs when OPP is not
supported by the platform at all.

Add a "use_pm_opp" flag to identify whether OPP is supported and use it to
control invoking the OPP APIs.

Fixes: 5b6272e0 ("PCI: qcom: Add OPP support to scale performance")
Link: https://lore.kernel.org/linux-pci/20240722131128.32470-1-manivannan.sadhasivam@linaro.orgSigned-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Mayank Rana <quic_mrana@quicinc.com>

drivers/pci/controller/dwc/pcie-qcom.c

@@ -261,6 +261,7 @@ struct qcom_pcie {
 	const struct qcom_pcie_cfg *cfg;
 	struct dentry *debugfs;
 	bool suspended;
+	bool use_pm_opp;
 };
 
 #define to_qcom_pcie(x)		dev_get_drvdata((x)->dev)
@@ -1433,7 +1434,7 @@ static void qcom_pcie_icc_opp_update(struct qcom_pcie *pcie)
 			dev_err(pci->dev, "Failed to set bandwidth for PCIe-MEM interconnect path: %d\n",
 				ret);
 		}
-	} else {
+	} else if (pcie->use_pm_opp) {
 		freq_mbps = pcie_dev_speed_mbps(pcie_link_speed[speed]);
 		if (freq_mbps < 0)
 			return;
@@ -1592,6 +1593,8 @@ static int qcom_pcie_probe(struct platform_device *pdev)
 				      max_freq);
 			goto err_pm_runtime_put;
 		}
+
+		pcie->use_pm_opp = true;
 	} else {
 		/* Skip ICC init if OPP is supported as it is handled by OPP */
 		ret = qcom_pcie_icc_init(pcie);
@@ -1683,7 +1686,7 @@ static int qcom_pcie_suspend_noirq(struct device *dev)
 		if (ret)
 			dev_err(dev, "Failed to disable CPU-PCIe interconnect path: %d\n", ret);
 
-		if (!pcie->icc_mem)
+		if (pcie->use_pm_opp)
 			dev_pm_opp_set_opp(pcie->pci->dev, NULL);
 	}
 	return ret;