linux-kernel - [PATCH v2] PCI: imx6: Save and restore MSI control of RC in suspend and resume

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Date:   Thu,  8 Dec 2022 14:05:34 +0800
From:   Richard Zhu <hongxing.zhu@....com>
To:     l.stach@...gutronix.de, bhelgaas@...gle.com,
        lorenzo.pieralisi@....com
Cc:     hongxing.zhu@....com, linux-pci@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kernel@...gutronix.de, linux-imx@....com
Subject: [PATCH v2] PCI: imx6: Save and restore MSI control of RC in suspend and resume

The MSI Enable bit controls delivery of MSI interrupts from components
below the Root Port. This bit might lost during the suspend, should be
re-stored during resume.

Save the MSI control during suspend, and restore it in resume.

Signed-off-by: Richard Zhu <hongxing.zhu@....com>
---
Changes v1-->v2:
New create one save/restore function, used save the setting in suspend and
restore the configuration in resume.
v1 https://patchwork.kernel.org/project/linux-pci/patch/1667289595-12440-1-git-send-email-hongxing.zhu@nxp.com/

---
 drivers/pci/controller/dwc/pci-imx6.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
index 1dde5c579edc..aa3096890c3b 100644
--- a/drivers/pci/controller/dwc/pci-imx6.c
+++ b/drivers/pci/controller/dwc/pci-imx6.c
@@ -76,6 +76,7 @@ struct imx6_pcie {
 	struct clk		*pcie;
 	struct clk		*pcie_aux;
 	struct regmap		*iomuxc_gpr;
+	u16			msi_ctrl;
 	u32			controller_id;
 	struct reset_control	*pciephy_reset;
 	struct reset_control	*apps_reset;
@@ -1042,6 +1043,26 @@ static void imx6_pcie_pm_turnoff(struct imx6_pcie *imx6_pcie)
 	usleep_range(1000, 10000);
 }
 
+static void imx6_pcie_msi_save_restore(struct imx6_pcie *imx6_pcie, bool save)
+{
+	u8 offset;
+	u16 val;
+	struct dw_pcie *pci = imx6_pcie->pci;
+
+	if (pci_msi_enabled()) {
+		offset = dw_pcie_find_capability(pci, PCI_CAP_ID_MSI);
+		if (save) {
+			val = dw_pcie_readw_dbi(pci, offset + PCI_MSI_FLAGS);
+			imx6_pcie->msi_ctrl = val;
+		} else {
+			dw_pcie_dbi_ro_wr_en(pci);
+			val = imx6_pcie->msi_ctrl;
+			dw_pcie_writew_dbi(pci, offset + PCI_MSI_FLAGS, val);
+			dw_pcie_dbi_ro_wr_dis(pci);
+		}
+	}
+}
+
 static int imx6_pcie_suspend_noirq(struct device *dev)
 {
 	struct imx6_pcie *imx6_pcie = dev_get_drvdata(dev);
@@ -1050,6 +1071,7 @@ static int imx6_pcie_suspend_noirq(struct device *dev)
 	if (!(imx6_pcie->drvdata->flags & IMX6_PCIE_FLAG_SUPPORTS_SUSPEND))
 		return 0;
 
+	imx6_pcie_msi_save_restore(imx6_pcie, true);
 	imx6_pcie_pm_turnoff(imx6_pcie);
 	imx6_pcie_stop_link(imx6_pcie->pci);
 	imx6_pcie_host_exit(pp);
@@ -1069,6 +1091,7 @@ static int imx6_pcie_resume_noirq(struct device *dev)
 	ret = imx6_pcie_host_init(pp);
 	if (ret)
 		return ret;
+	imx6_pcie_msi_save_restore(imx6_pcie, false);
 	dw_pcie_setup_rc(pp);
 
 	if (imx6_pcie->link_is_up)
-- 
2.25.1