linux-kernel - [PATCH v2 10/10] PCI: qcom: Implement shutdown() callback to properly reset the endpoint devices

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Message-Id: <20240401-pci-epf-rework-v2-10-970dbe90b99d@linaro.org>
Date: Mon, 01 Apr 2024 21:20:36 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Lorenzo Pieralisi <lpieralisi@...nel.org>, 
 Krzysztof Wilczyński <kw@...ux.com>, 
 Rob Herring <robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>, 
 Kishon Vijay Abraham I <kishon@...nel.org>, 
 Thierry Reding <thierry.reding@...il.com>, 
 Jonathan Hunter <jonathanh@...dia.com>, Jingoo Han <jingoohan1@...il.com>
Cc: linux-pci@...r.kernel.org, linux-arm-msm@...r.kernel.org, 
 linux-kernel@...r.kernel.org, mhi@...ts.linux.dev, 
 linux-tegra@...r.kernel.org, Niklas Cassel <cassel@...nel.org>, 
 Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Subject: [PATCH v2 10/10] PCI: qcom: Implement shutdown() callback to
 properly reset the endpoint devices

PCIe host controller drivers are supposed to properly reset the endpoint
devices during host shutdown/reboot. Currently, Qcom driver doesn't do
anything during host shutdown/reboot, resulting in both PERST# and refclk
getting disabled at the same time. This prevents the endpoint device
firmware to properly reset the state machine. Because, if the refclk is
cutoff immediately along with PERST#, access to device specific registers
within the endpoint will result in a firmware crash.

To address this issue, let's call qcom_pcie_host_deinit() inside the
shutdown callback, that asserts PERST# and then cuts off the refclk with a
delay of 1ms, thus allowing the endpoint device firmware to properly
cleanup the state machine.

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
---
 drivers/pci/controller/dwc/pcie-qcom.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
index 14772edcf0d3..b2803978c0ad 100644
--- a/drivers/pci/controller/dwc/pcie-qcom.c
+++ b/drivers/pci/controller/dwc/pcie-qcom.c
@@ -1655,6 +1655,13 @@ static int qcom_pcie_resume_noirq(struct device *dev)
 	return 0;
 }
 
+static void qcom_pcie_shutdown(struct platform_device *pdev)
+{
+	struct qcom_pcie *pcie = platform_get_drvdata(pdev);
+
+	qcom_pcie_host_deinit(&pcie->pci->pp);
+}
+
 static const struct of_device_id qcom_pcie_match[] = {
 	{ .compatible = "qcom,pcie-apq8064", .data = &cfg_2_1_0 },
 	{ .compatible = "qcom,pcie-apq8084", .data = &cfg_1_0_0 },
@@ -1708,5 +1715,6 @@ static struct platform_driver qcom_pcie_driver = {
 		.pm = &qcom_pcie_pm_ops,
 		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
 	},
+	.shutdown = qcom_pcie_shutdown,
 };
 builtin_platform_driver(qcom_pcie_driver);

-- 
2.25.1