PCI: qcom: Use frequency and level based OPP lookup

PCIe link configurations such as 8GT/s x2 and 16GT/s x1 may operate at the
same frequency, but differ in other characteristics like RPMh votes.  But
the existing OPP selection which is solely based on frequency (the 'opp-hz'
DT property) cannot distinguish between such cases.

Hence, use the newly introduced dev_pm_opp_find_key_exact() API to match
both frequency and level (the 'opp-level' property) when selecting an OPP,
here level indicates PCIe data rate.

To support older device trees where opp-level is not defined, check if
opp-level is present or not using dev_pm_opp_find_level_exact(). If
not present fallback to frequency only match.

Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
[mani: zero initialize dev_pm_opp_key struct]
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
[bhelgaas: add 'opp-hz' and 'opp-level' in commit log]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://patch.msgid.link/20251013-opp_pcie-v5-5-eb64db2b4bd3@oss.qualcomm.com

Author: krishnachaitanya-linux

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

@@ -1565,6 +1565,7 @@ static void qcom_pcie_icc_opp_update(struct qcom_pcie *pcie)
 {
 	u32 offset, status, width, speed;
 	struct dw_pcie *pci = pcie->pci;
+	struct dev_pm_opp_key key = {};
 	unsigned long freq_kbps;
 	struct dev_pm_opp *opp;
 	int ret, freq_mbps;
@@ -1592,8 +1593,20 @@ static void qcom_pcie_icc_opp_update(struct qcom_pcie *pcie)
 			return;
 
 		freq_kbps = freq_mbps * KILO;
-		opp = dev_pm_opp_find_freq_exact(pci->dev, freq_kbps * width,
-						 true);
+		opp = dev_pm_opp_find_level_exact(pci->dev, speed);
+		if (IS_ERR(opp)) {
+			 /* opp-level is not defined use only frequency */
+			opp = dev_pm_opp_find_freq_exact(pci->dev, freq_kbps * width,
+							 true);
+		} else {
+			/* put opp-level OPP */
+			dev_pm_opp_put(opp);
+
+			key.freq = freq_kbps * width;
+			key.level = speed;
+			key.bw = 0;
+			opp = dev_pm_opp_find_key_exact(pci->dev, &key, true);
+		}
 		if (!IS_ERR(opp)) {
 			ret = dev_pm_opp_set_opp(pci->dev, opp);
 			if (ret)