PCI: tegra194: Add interconnect support in Tegra234

Add support to request DRAM bandwidth (BW) with Memory Interconnect
in Tegra234 SoC. The DRAM BW required for different modes depends on
the link speed (Gen-1/2/3/4) and width/lanes (x1/x2/x4/x8).
Currently, the DRAM frequency is always set to the maximum available
but that results in the highest power consumption.
The Memory Interconnect is a software feature which uses Interconnect
framework (ICC). It adds the capability for Memory Controller (MC)
clients to request bandwidth and therefore scale DRAM frequency
dynamically depending on the required link speed so that the DRAM
energy consumption can be optimized.

Suggested-by: Manikanta Maddireddy <mmaddireddy@nvidia.com>
Signed-off-by: Sumit Gupta <sumitg@nvidia.com>
Acked-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>

Author: Sumit Gupta

drivers/pci/controller/dwc/pcie-tegra194.c

@@ -14,6 +14,7 @@
 #include <linux/delay.h>
 #include <linux/gpio.h>
 #include <linux/gpio/consumer.h>
+#include <linux/interconnect.h>
 #include <linux/interrupt.h>
 #include <linux/iopoll.h>
 #include <linux/kernel.h>
@@ -288,6 +289,7 @@ struct tegra_pcie_dw {
 	unsigned int pex_rst_irq;
 	int ep_state;
 	long link_status;
+	struct icc_path *icc_path;
 };
 
 static inline struct tegra_pcie_dw *to_tegra_pcie(struct dw_pcie *pci)
@@ -310,6 +312,27 @@ struct tegra_pcie_soc {
 	enum dw_pcie_device_mode mode;
 };
 
+static void tegra_pcie_icc_set(struct tegra_pcie_dw *pcie)
+{
+	struct dw_pcie *pci = &pcie->pci;
+	u32 val, speed, width;
+
+	val = dw_pcie_readw_dbi(pci, pcie->pcie_cap_base + PCI_EXP_LNKSTA);
+
+	speed = FIELD_GET(PCI_EXP_LNKSTA_CLS, val);
+	width = FIELD_GET(PCI_EXP_LNKSTA_NLW, val);
+
+	val = width * (PCIE_SPEED2MBS_ENC(pcie_link_speed[speed]) / BITS_PER_BYTE);
+
+	if (icc_set_bw(pcie->icc_path, MBps_to_icc(val), 0))
+		dev_err(pcie->dev, "can't set bw[%u]\n", val);
+
+	if (speed >= ARRAY_SIZE(pcie_gen_freq))
+		speed = 0;
+
+	clk_set_rate(pcie->core_clk, pcie_gen_freq[speed]);
+}
+
 static void apply_bad_link_workaround(struct dw_pcie_rp *pp)
 {
 	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
@@ -453,18 +476,12 @@ static irqreturn_t tegra_pcie_ep_irq_thread(int irq, void *arg)
 	struct tegra_pcie_dw *pcie = arg;
 	struct dw_pcie_ep *ep = &pcie->pci.ep;
 	struct dw_pcie *pci = &pcie->pci;
-	u32 val, speed;
+	u32 val;
 
 	if (test_and_clear_bit(0, &pcie->link_status))
 		dw_pcie_ep_linkup(ep);
 
-	speed = dw_pcie_readw_dbi(pci, pcie->pcie_cap_base + PCI_EXP_LNKSTA) &
-		PCI_EXP_LNKSTA_CLS;
-
-	if (speed >= ARRAY_SIZE(pcie_gen_freq))
-		speed = 0;
-
-	clk_set_rate(pcie->core_clk, pcie_gen_freq[speed]);
+	tegra_pcie_icc_set(pcie);
 
 	if (pcie->of_data->has_ltr_req_fix)
 		return IRQ_HANDLED;
@@ -950,9 +967,9 @@ static int tegra_pcie_dw_host_init(struct dw_pcie_rp *pp)
 
 static int tegra_pcie_dw_start_link(struct dw_pcie *pci)
 {
-	u32 val, offset, speed, tmp;
 	struct tegra_pcie_dw *pcie = to_tegra_pcie(pci);
 	struct dw_pcie_rp *pp = &pci->pp;
+	u32 val, offset, tmp;
 	bool retry = true;
 
 	if (pcie->of_data->mode == DW_PCIE_EP_TYPE) {
@@ -1023,13 +1040,7 @@ static int tegra_pcie_dw_start_link(struct dw_pcie *pci)
 		goto retry_link;
 	}
 
-	speed = dw_pcie_readw_dbi(pci, pcie->pcie_cap_base + PCI_EXP_LNKSTA) &
-		PCI_EXP_LNKSTA_CLS;
-
-	if (speed >= ARRAY_SIZE(pcie_gen_freq))
-		speed = 0;
-
-	clk_set_rate(pcie->core_clk, pcie_gen_freq[speed]);
+	tegra_pcie_icc_set(pcie);
 
 	tegra_pcie_enable_interrupts(pp);
 
@@ -2233,6 +2244,14 @@ static int tegra_pcie_dw_probe(struct platform_device *pdev)
 
 	platform_set_drvdata(pdev, pcie);
 
+	pcie->icc_path = devm_of_icc_get(&pdev->dev, "write");
+	ret = PTR_ERR_OR_ZERO(pcie->icc_path);
+	if (ret) {
+		tegra_bpmp_put(pcie->bpmp);
+		dev_err_probe(&pdev->dev, ret, "failed to get write interconnect\n");
+		return ret;
+	}
+
 	switch (pcie->of_data->mode) {
 	case DW_PCIE_RC_TYPE:
 		ret = devm_request_irq(dev, pp->irq, tegra_pcie_rp_irq_handler,