linux-kernel - [PATCH V3 18/21] PCI: tegra194: Don't force the device into the D0 state before L2

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Date:   Fri, 14 Oct 2022 00:08:51 +0530
From:   Vidya Sagar <vidyas@...dia.com>
To:     <lpieralisi@...nel.org>, <robh@...nel.org>, <kw@...ux.com>,
        <bhelgaas@...gle.com>, <thierry.reding@...il.com>,
        <jonathanh@...dia.com>, <kishon@...com>, <vkoul@...nel.org>,
        <mani@...nel.org>, <Sergey.Semin@...kalelectronics.ru>,
        <ffclaire1224@...il.com>
CC:     <linux-pci@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-phy@...ts.infradead.org>,
        <kthota@...dia.com>, <mmaddireddy@...dia.com>, <vidyas@...dia.com>,
        <sagar.tv@...il.com>
Subject: [PATCH V3 18/21] PCI: tegra194: Don't force the device into the D0 state before L2

As per PCIe CEM spec rev 4.0 ver 1.0 sec 2.3, the PCIe endpoint device
should be in D3 state to assert wake# pin. This takes precedence over PCI
Express Base r4.0 v1.0 September 27-2017, 5.2 Link State Power Management
which states that the device can be put into D0 state before taking the
link to L2 state. So, to enable the wake functionality for endpoints, do
not force the devices to D0 state before taking the link to L2 state.
There is no functional issue with the endpoints where the link doesn't go
into L2 state (the reason why the earlier change was made in the first
place) as the root port proceeds with the usual flow post PME timeout.

Fixes: 56e15a238d92 ("PCI: tegra: Add Tegra194 PCIe support")
Signed-off-by: Vidya Sagar <vidyas@...dia.com>
---
V3:
* This is a new patch in this series

 drivers/pci/controller/dwc/pcie-tegra194.c | 41 ----------------------
 1 file changed, 41 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-tegra194.c b/drivers/pci/controller/dwc/pcie-tegra194.c
index 7890e0c0c0d2..3baf1a26fe68 100644
--- a/drivers/pci/controller/dwc/pcie-tegra194.c
+++ b/drivers/pci/controller/dwc/pcie-tegra194.c
@@ -1358,44 +1358,6 @@ static int tegra_pcie_bpmp_set_pll_state(struct tegra_pcie_dw *pcie,
 	return 0;
 }
 
-static void tegra_pcie_downstream_dev_to_D0(struct tegra_pcie_dw *pcie)
-{
-	struct dw_pcie_rp *pp = &pcie->pci.pp;
-	struct pci_bus *child, *root_bus = NULL;
-	struct pci_dev *pdev;
-
-	/*
-	 * link doesn't go into L2 state with some of the endpoints with Tegra
-	 * if they are not in D0 state. So, need to make sure that immediate
-	 * downstream devices are in D0 state before sending PME_TurnOff to put
-	 * link into L2 state.
-	 * This is as per PCI Express Base r4.0 v1.0 September 27-2017,
-	 * 5.2 Link State Power Management (Page #428).
-	 */
-
-	list_for_each_entry(child, &pp->bridge->bus->children, node) {
-		/* Bring downstream devices to D0 if they are not already in */
-		if (child->parent == pp->bridge->bus) {
-			root_bus = child;
-			break;
-		}
-	}
-
-	if (!root_bus) {
-		dev_err(pcie->dev, "Failed to find downstream devices\n");
-		return;
-	}
-
-	list_for_each_entry(pdev, &root_bus->devices, bus_list) {
-		if (PCI_SLOT(pdev->devfn) == 0) {
-			if (pci_set_power_state(pdev, PCI_D0))
-				dev_err(pcie->dev,
-					"Failed to transition %s to D0 state\n",
-					dev_name(&pdev->dev));
-		}
-	}
-}
-
 static int tegra_pcie_get_slot_regulators(struct tegra_pcie_dw *pcie)
 {
 	pcie->slot_ctl_3v3 = devm_regulator_get_optional(pcie->dev, "vpcie3v3");
@@ -1725,7 +1687,6 @@ static void tegra_pcie_dw_pme_turnoff(struct tegra_pcie_dw *pcie)
 
 static void tegra_pcie_deinit_controller(struct tegra_pcie_dw *pcie)
 {
-	tegra_pcie_downstream_dev_to_D0(pcie);
 	dw_pcie_host_deinit(&pcie->pci.pp);
 	tegra_pcie_dw_pme_turnoff(pcie);
 	tegra_pcie_unconfig_controller(pcie);
@@ -2486,7 +2447,6 @@ static int tegra_pcie_dw_suspend_noirq(struct device *dev)
 	if (!pcie->link_state && !pcie->slot_pluggable)
 		return 0;
 
-	tegra_pcie_downstream_dev_to_D0(pcie);
 	tegra_pcie_dw_pme_turnoff(pcie);
 	tegra_pcie_unconfig_controller(pcie);
 
@@ -2565,7 +2525,6 @@ static void tegra_pcie_dw_shutdown(struct platform_device *pdev)
 		if (pcie->slot_pluggable)
 			unregister_gpio_hotplug_slot(&pcie->hp_slot);
 		debugfs_remove_recursive(pcie->debugfs);
-		tegra_pcie_downstream_dev_to_D0(pcie);
 
 		disable_irq(pcie->pci.pp.irq);
 		if (IS_ENABLED(CONFIG_PCI_MSI))
-- 
2.17.1