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Message-ID: <dca49572-dc77-58df-1bd1-b0e897191c87@quicinc.com>
Date: Tue, 16 Jul 2024 09:34:13 +0530
From: Krishna Chaitanya Chundru <quic_krichai@...cinc.com>
To: <manivannan.sadhasivam@...aro.org>,
Lorenzo Pieralisi
<lpieralisi@...nel.org>,
Krzysztof Wilczyński
<kw@...ux.com>,
Rob Herring <robh@...nel.org>, Bjorn Helgaas
<bhelgaas@...gle.com>,
Krzysztof Kozlowski <krzk+dt@...nel.org>,
Conor Dooley
<conor+dt@...nel.org>,
Kishon Vijay Abraham I <kishon@...nel.org>,
Bjorn
Andersson <andersson@...nel.org>,
Konrad Dybcio <konrad.dybcio@...aro.org>
CC: <linux-pci@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>,
<linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>
Subject: Re: [PATCH 13/14] PCI: qcom: Simulate PCIe hotplug using 'global'
interrupt
On 7/15/2024 11:03 PM, Manivannan Sadhasivam via B4 Relay wrote:
> From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
>
> Historically, Qcom PCIe RC controllers lack standard hotplug support. So
> when an endpoint is attached to the SoC, users have to rescan the bus
> manually to enumerate the device. But this can be avoided by simulating the
> PCIe hotplug using Qcom specific way.
>
> Qcom PCIe RC controllers are capable of generating the 'global' SPI
> interrupt to the host CPUs. The device driver can use this event to
> identify events such as PCIe link specific events, safety events etc...
>
> One such event is the PCIe Link up event generated when an endpoint is
> detected on the bus and the Link is 'up'. This event can be used to
> simulate the PCIe hotplug in the Qcom SoCs.
>
> So add support for capturing the PCIe Link up event using the 'global'
> interrupt in the driver. Once the Link up event is received, the bus
> underneath the host bridge is scanned to enumerate PCIe endpoint devices,
> thus simulating hotplug.
>
> All of the Qcom SoCs have only one rootport per controller instance. So
> only a single 'Link up' event is generated for the PCIe controller.
>
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> ---
> drivers/pci/controller/dwc/pcie-qcom.c | 55 ++++++++++++++++++++++++++++++++++
> 1 file changed, 55 insertions(+)
>
> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> index 0180edf3310e..38ed411d2052 100644
> --- a/drivers/pci/controller/dwc/pcie-qcom.c
> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> @@ -50,6 +50,9 @@
> #define PARF_AXI_MSTR_WR_ADDR_HALT_V2 0x1a8
> #define PARF_Q2A_FLUSH 0x1ac
> #define PARF_LTSSM 0x1b0
> +#define PARF_INT_ALL_STATUS 0x224
> +#define PARF_INT_ALL_CLEAR 0x228
> +#define PARF_INT_ALL_MASK 0x22c
> #define PARF_SID_OFFSET 0x234
> #define PARF_BDF_TRANSLATE_CFG 0x24c
> #define PARF_SLV_ADDR_SPACE_SIZE 0x358
> @@ -121,6 +124,9 @@
> /* PARF_LTSSM register fields */
> #define LTSSM_EN BIT(8)
>
> +/* PARF_INT_ALL_{STATUS/CLEAR/MASK} register fields */
> +#define PARF_INT_ALL_LINK_UP BIT(13)
> +
> /* PARF_NO_SNOOP_OVERIDE register fields */
> #define WR_NO_SNOOP_OVERIDE_EN BIT(1)
> #define RD_NO_SNOOP_OVERIDE_EN BIT(3)
> @@ -260,6 +266,7 @@ struct qcom_pcie {
> struct icc_path *icc_cpu;
> const struct qcom_pcie_cfg *cfg;
> struct dentry *debugfs;
> + int global_irq;
> bool suspended;
> };
>
> @@ -1488,6 +1495,29 @@ static void qcom_pcie_init_debugfs(struct qcom_pcie *pcie)
> qcom_pcie_link_transition_count);
> }
>
> +static irqreturn_t qcom_pcie_global_irq_thread(int irq, void *data)
> +{
> + struct qcom_pcie *pcie = data;
> + struct dw_pcie_rp *pp = &pcie->pci->pp; > + struct device *dev = pcie->pci->dev;
> + u32 status = readl_relaxed(pcie->parf + PARF_INT_ALL_STATUS);
> +
> + writel_relaxed(status, pcie->parf + PARF_INT_ALL_CLEAR);
> +
> + if (FIELD_GET(PARF_INT_ALL_LINK_UP, status)) {
> + dev_dbg(dev, "Received Link up event. Starting enumeration!\n");
> + /* Rescan the bus to enumerate endpoint devices */
> + pci_lock_rescan_remove();
> + pci_rescan_bus(pp->bridge->bus);
There can be chances of getting link up interrupt before PCIe framework
starts enumeration and at that time bridge-> bus is not created and
cause NULL point access.
Please have a check for this.
- Krishna Chaitanya.
> + pci_unlock_rescan_remove();
> + } else {
> + dev_err(dev, "Received unknown event. INT_STATUS: 0x%08x\n",
> + status);
> + }
> +
> + return IRQ_HANDLED;
> +}
> +
> static int qcom_pcie_probe(struct platform_device *pdev)
> {
> const struct qcom_pcie_cfg *pcie_cfg;
> @@ -1498,6 +1528,7 @@ static int qcom_pcie_probe(struct platform_device *pdev)
> struct dw_pcie_rp *pp;
> struct resource *res;
> struct dw_pcie *pci;
> + char *name;
> int ret;
>
> pcie_cfg = of_device_get_match_data(dev);
> @@ -1617,6 +1648,28 @@ static int qcom_pcie_probe(struct platform_device *pdev)
> goto err_phy_exit;
> }
>
> + name = devm_kasprintf(dev, GFP_KERNEL, "qcom_pcie_global_irq%d",
> + pci_domain_nr(pp->bridge->bus));
> + if (!name) {
> + ret = -ENOMEM;
> + goto err_host_deinit;
> + }
> +
> + pcie->global_irq = platform_get_irq_byname_optional(pdev, "global");
> + if (pcie->global_irq > 0) {
> + ret = devm_request_threaded_irq(&pdev->dev, pcie->global_irq,
> + NULL,
> + qcom_pcie_global_irq_thread,
> + IRQF_ONESHOT, name, pcie);
> + if (ret) {
> + dev_err_probe(&pdev->dev, ret,
> + "Failed to request Global IRQ\n");
> + goto err_host_deinit;
> + }
> +
> + writel_relaxed(PARF_INT_ALL_LINK_UP, pcie->parf + PARF_INT_ALL_MASK);
> + }
> +
> qcom_pcie_icc_opp_update(pcie);
>
> if (pcie->mhi)
> @@ -1624,6 +1677,8 @@ static int qcom_pcie_probe(struct platform_device *pdev)
>
> return 0;
>
> +err_host_deinit:
> + dw_pcie_host_deinit(pp);
> err_phy_exit:
> phy_exit(pcie->phy);
> err_pm_runtime_put:
>
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