Re: [PATCH 13/14] PCI: qcom: Simulate PCIe hotplug using 'global' interrupt

[neil . armstrong]

On 15/07/2024 19:33, Manivannan Sadhasivam via B4 Relay wrote:
> From: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx>
>
> 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@xxxxxxxxxx>
> ---
>   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;

I think you can drop this, the irq number is no more needed after probe

>   	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);
> +		pci_unlock_rescan_remove();
> +	} else {
> +		dev_err(dev, "Received unknown event. INT_STATUS: 0x%08x\n",
> +			status);

Can this happen ? perhaps dev_warn_once instead ?

> +	}
> +
> +	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);

Is this available on all PCIe RC core versions ?
perhaps this should be moved into a callback of ops_1_9_0 for now ?

> +	}
> +
>   	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: