PCI: qcom-ep: Add ICC bandwidth voting support

Add support for voting interconnect (ICC) bandwidth based
on the link speed and width.

This commit is inspired from the basic interconnect support added
to pcie-qcom driver in commit c4860af ("PCI: qcom: Add basic
interconnect support").

The interconnect support is kept optional to be backward compatible
with legacy device trees.

[kwilczynski: add missing kernel-doc for the icc_mem variable]
Link: https://lore.kernel.org/linux-pci/1689751218-24492-5-git-send-email-quic_krichai@quicinc.com
Signed-off-by: Krishna chaitanya chundru <quic_krichai@quicinc.com>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

Author: Krishna chaitanya chundru

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

@@ -13,6 +13,7 @@
 #include <linux/debugfs.h>
 #include <linux/delay.h>
 #include <linux/gpio/consumer.h>
+#include <linux/interconnect.h>
 #include <linux/mfd/syscon.h>
 #include <linux/phy/pcie.h>
 #include <linux/phy/phy.h>
@@ -133,6 +134,11 @@
 #define CORE_RESET_TIME_US_MAX			1005
 #define WAKE_DELAY_US				2000 /* 2 ms */
 
+#define PCIE_GEN1_BW_MBPS			250
+#define PCIE_GEN2_BW_MBPS			500
+#define PCIE_GEN3_BW_MBPS			985
+#define PCIE_GEN4_BW_MBPS			1969
+
 #define to_pcie_ep(x)				dev_get_drvdata((x)->dev)
 
 enum qcom_pcie_ep_link_status {
@@ -155,6 +161,7 @@ enum qcom_pcie_ep_link_status {
  * @wake: WAKE# GPIO
  * @phy: PHY controller block
  * @debugfs: PCIe Endpoint Debugfs directory
+ * @icc_mem: Handle to an interconnect path between PCIe and MEM
  * @clks: PCIe clocks
  * @num_clks: PCIe clocks count
  * @perst_en: Flag for PERST enable
@@ -178,6 +185,8 @@ struct qcom_pcie_ep {
 	struct phy *phy;
 	struct dentry *debugfs;
 
+	struct icc_path *icc_mem;
+
 	struct clk_bulk_data *clks;
 	int num_clks;
 
@@ -253,8 +262,49 @@ static void qcom_pcie_dw_stop_link(struct dw_pcie *pci)
 	disable_irq(pcie_ep->perst_irq);
 }
 
+static void qcom_pcie_ep_icc_update(struct qcom_pcie_ep *pcie_ep)
+{
+	struct dw_pcie *pci = &pcie_ep->pci;
+	u32 offset, status, bw;
+	int speed, width;
+	int ret;
+
+	if (!pcie_ep->icc_mem)
+		return;
+
+	offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
+	status = readw(pci->dbi_base + offset + PCI_EXP_LNKSTA);
+
+	speed = FIELD_GET(PCI_EXP_LNKSTA_CLS, status);
+	width = FIELD_GET(PCI_EXP_LNKSTA_NLW, status);
+
+	switch (speed) {
+	case 1:
+		bw = MBps_to_icc(PCIE_GEN1_BW_MBPS);
+		break;
+	case 2:
+		bw = MBps_to_icc(PCIE_GEN2_BW_MBPS);
+		break;
+	case 3:
+		bw = MBps_to_icc(PCIE_GEN3_BW_MBPS);
+		break;
+	default:
+		dev_warn(pci->dev, "using default GEN4 bandwidth\n");
+		fallthrough;
+	case 4:
+		bw = MBps_to_icc(PCIE_GEN4_BW_MBPS);
+		break;
+	}
+
+	ret = icc_set_bw(pcie_ep->icc_mem, 0, width * bw);
+	if (ret)
+		dev_err(pci->dev, "failed to set interconnect bandwidth: %d\n",
+			ret);
+}
+
 static int qcom_pcie_enable_resources(struct qcom_pcie_ep *pcie_ep)
 {
+	struct dw_pcie *pci = &pcie_ep->pci;
 	int ret;
 
 	ret = clk_bulk_prepare_enable(pcie_ep->num_clks, pcie_ep->clks);
@@ -277,8 +327,24 @@ static int qcom_pcie_enable_resources(struct qcom_pcie_ep *pcie_ep)
 	if (ret)
 		goto err_phy_exit;
 
+	/*
+	 * Some Qualcomm platforms require interconnect bandwidth constraints
+	 * to be set before enabling interconnect clocks.
+	 *
+	 * Set an initial peak bandwidth corresponding to single-lane Gen 1
+	 * for the pcie-mem path.
+	 */
+	ret = icc_set_bw(pcie_ep->icc_mem, 0, MBps_to_icc(PCIE_GEN1_BW_MBPS));
+	if (ret) {
+		dev_err(pci->dev, "failed to set interconnect bandwidth: %d\n",
+			ret);
+		goto err_phy_off;
+	}
+
 	return 0;
 
+err_phy_off:
+	phy_power_off(pcie_ep->phy);
 err_phy_exit:
 	phy_exit(pcie_ep->phy);
 err_disable_clk:
@@ -289,6 +355,7 @@ static int qcom_pcie_enable_resources(struct qcom_pcie_ep *pcie_ep)
 
 static void qcom_pcie_disable_resources(struct qcom_pcie_ep *pcie_ep)
 {
+	icc_set_bw(pcie_ep->icc_mem, 0, 0);
 	phy_power_off(pcie_ep->phy);
 	phy_exit(pcie_ep->phy);
 	clk_bulk_disable_unprepare(pcie_ep->num_clks, pcie_ep->clks);
@@ -550,6 +617,10 @@ static int qcom_pcie_ep_get_resources(struct platform_device *pdev,
 	if (IS_ERR(pcie_ep->phy))
 		ret = PTR_ERR(pcie_ep->phy);
 
+	pcie_ep->icc_mem = devm_of_icc_get(dev, "pcie-mem");
+	if (IS_ERR(pcie_ep->icc_mem))
+		ret = PTR_ERR(pcie_ep->icc_mem);
+
 	return ret;
 }
 
@@ -573,6 +644,7 @@ static irqreturn_t qcom_pcie_ep_global_irq_thread(int irq, void *data)
 	} else if (FIELD_GET(PARF_INT_ALL_BME, status)) {
 		dev_dbg(dev, "Received BME event. Link is enabled!\n");
 		pcie_ep->link_status = QCOM_PCIE_EP_LINK_ENABLED;
+		qcom_pcie_ep_icc_update(pcie_ep);
 		pci_epc_bme_notify(pci->ep.epc);
 	} else if (FIELD_GET(PARF_INT_ALL_PM_TURNOFF, status)) {
 		dev_dbg(dev, "Received PM Turn-off event! Entering L23\n");