linux-kernel - [PATCH 10/11] PCI: qcom-ep: Rework {start/stop}

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Message-Id: <20240314-pci-epf-rework-v1-10-6134e6c1d491@linaro.org>
Date: Thu, 14 Mar 2024 20:53:49 +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>, 
 Gustavo Pimentel <gustavo.pimentel@...opsys.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, 
 Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Subject: [PATCH 10/11] PCI: qcom-ep: Rework {start/stop}_link() callbacks
 implementation

DWC specific start_link() and stop_link() callbacks are supposed to start
and stop the link training of the PCIe bus. But the current implementation
of this driver enables/disables the PERST# IRQ.

Even though this is not causing any issues, this creates inconsistency
among the controller drivers. So for the sake of consistency, let's just
start/stop the link training in these callbacks.

Also, PERST# IRQ is now enabled from the start itself, thus allowing the
controller driver to initialize the registers when PERST# gets deasserted
without waiting for the user intervention though configfs.

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
---
 drivers/pci/controller/dwc/pcie-qcom-ep.c | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-qcom-ep.c b/drivers/pci/controller/dwc/pcie-qcom-ep.c
index 811f250e967a..653e4ace0a07 100644
--- a/drivers/pci/controller/dwc/pcie-qcom-ep.c
+++ b/drivers/pci/controller/dwc/pcie-qcom-ep.c
@@ -122,6 +122,9 @@
 /* PARF_CFG_BITS register fields */
 #define PARF_CFG_BITS_REQ_EXIT_L1SS_MSI_LTR_EN	BIT(1)
 
+/* PARF_LTSSM register fields */
+#define LTSSM_EN				BIT(8)
+
 /* ELBI registers */
 #define ELBI_SYS_STTS				0x08
 #define ELBI_CS2_ENABLE				0xa4
@@ -250,8 +253,12 @@ static int qcom_pcie_dw_link_up(struct dw_pcie *pci)
 static int qcom_pcie_dw_start_link(struct dw_pcie *pci)
 {
 	struct qcom_pcie_ep *pcie_ep = to_pcie_ep(pci);
+	u32 val;
 
-	enable_irq(pcie_ep->perst_irq);
+	/* Enable LTSSM */
+	val = readl_relaxed(pcie_ep->parf + PARF_LTSSM);
+	val |= LTSSM_EN;
+	writel_relaxed(val, pcie_ep->parf + PARF_LTSSM);
 
 	return 0;
 }
@@ -259,8 +266,12 @@ static int qcom_pcie_dw_start_link(struct dw_pcie *pci)
 static void qcom_pcie_dw_stop_link(struct dw_pcie *pci)
 {
 	struct qcom_pcie_ep *pcie_ep = to_pcie_ep(pci);
+	u32 val;
 
-	disable_irq(pcie_ep->perst_irq);
+	/* Disable LTSSM */
+	val = readl_relaxed(pcie_ep->parf + PARF_LTSSM);
+	val &= ~LTSSM_EN;
+	writel_relaxed(val, pcie_ep->parf + PARF_LTSSM);
 }
 
 static void qcom_pcie_dw_write_dbi2(struct dw_pcie *pci, void __iomem *base,
@@ -484,11 +495,6 @@ static int qcom_pcie_perst_deassert(struct dw_pcie *pci)
 
 	dw_pcie_ep_init_notify(&pcie_ep->pci.ep);
 
-	/* Enable LTSSM */
-	val = readl_relaxed(pcie_ep->parf + PARF_LTSSM);
-	val |= BIT(8);
-	writel_relaxed(val, pcie_ep->parf + PARF_LTSSM);
-
 	return 0;
 
 err_disable_resources:
@@ -707,7 +713,6 @@ static int qcom_pcie_ep_enable_irq_resources(struct platform_device *pdev,
 	}
 
 	pcie_ep->perst_irq = gpiod_to_irq(pcie_ep->reset);
-	irq_set_status_flags(pcie_ep->perst_irq, IRQ_NOAUTOEN);
 	ret = devm_request_threaded_irq(&pdev->dev, pcie_ep->perst_irq, NULL,
 					qcom_pcie_ep_perst_irq_thread,
 					IRQF_TRIGGER_HIGH | IRQF_ONESHOT,

-- 
2.25.1