Hi Lorenzo,

-----Original Message-----
From: Lorenzo Pieralisi <redacted>
Sent: Monday, June 21, 2021 10:23 PM
To: Thokala, Srikanth <srikanth.thokala@intel.com>; maz@kernel.org
Cc: robh+dt@kernel.org; linux-pci@vger.kernel.org;
devicetree@vger.kernel.org; andriy.shevchenko@linux.intel.com;
mgross@linux.intel.com; Raja Subramanian, Lakshmi Bai
[off-list ref]; Sangannavar, Mallikarjunappa
[off-list ref]; kw@linux.com
Subject: Re: [PATCH v10 2/2] PCI: keembay: Add support for Intel Keem Bay

[+Marc]

On Mon, Jun 07, 2021 at 09:10:44PM +0530, srikanth.thokala@intel.com
wrote:
[...]

quoted

+static void keembay_pcie_msi_irq_handler(struct irq_desc *desc)
+{
+	struct keembay_pcie *pcie = irq_desc_get_handler_data(desc);
+	struct irq_chip *chip = irq_desc_get_chip(desc);
+	u32 val, mask, status;
+	struct pcie_port *pp;
+
+	chained_irq_enter(chip, desc);
+
+	pp = &pcie->pci.pp;
+	val = readl(pcie->apb_base + PCIE_REGS_INTERRUPT_STATUS);
+	mask = readl(pcie->apb_base + PCIE_REGS_INTERRUPT_ENABLE);
+
+	status = val & mask;
+
+	if (status & MSI_CTRL_INT) {
+		dw_handle_msi_irq(pp);
+		writel(status, pcie->apb_base + PCIE_REGS_INTERRUPT_STATUS);
+	}
+
+	chained_irq_exit(chip, desc);
+}
+
+static int keembay_pcie_setup_msi_irq(struct keembay_pcie *pcie)
+{
+	struct dw_pcie *pci = &pcie->pci;
+	struct device *dev = pci->dev;
+	struct platform_device *pdev = to_platform_device(dev);
+	int irq;
+
+	irq = platform_get_irq_byname(pdev, "pcie");
+	if (irq < 0)
+		return irq;
+
+	irq_set_chained_handler_and_data(irq, keembay_pcie_msi_irq_handler,
+					 pcie);
+

Ok this is yet another DWC MSI incantation and given that Marc worked
hard consolidating them let's have a look before we merge it.

IIUC - this IP relies on the DWC logic to handle MSIs + custom
registers to detect a pending MSI IRQ because the logic in
dw_chained_msi_irq() is *not* enough so you have to register
a driver specific chained handler. This looks similar to the dra7xx
driver MSI handling but I am not entirely convinced it is needed.

I assume this code in keembay_pcie_msi_irq_handler() is required
owing to additional IP logic on top of the standard DWC IP, in
particular the PCIE_REGS_INTERRUPT_STATUS write to "clear" the
IRQ.

We need more insights before merging it so please provide them.

pp = &pcie->pci.pp;
val = readl(pcie->apb_base + PCIE_REGS_INTERRUPT_STATUS);
mask = readl(pcie->apb_base + PCIE_REGS_INTERRUPT_ENABLE);

status = val & mask;

if (status & MSI_CTRL_INT) {
	dw_handle_msi_irq(pp);
	writel(status, pcie->apb_base + PCIE_REGS_INTERRUPT_STATUS);
}

Yes, your understanding is correct.

Additional registers PCIE_REGS_INTERRUPT_ENABLE/_STATUS are provided
by IP to control the interrupts.

To receive MSI interrupts, SW must enable bit '8' of _ENABLE register.
And once a MSI is raised by the End point, bit '8' of _STATUS register
will be set and it needs to be cleared after servicing the interrupt.

Thanks!
Srikanth

Thanks,
Lorenzo

quoted

+static void keembay_pcie_ep_init(struct dw_pcie_ep *ep)
+{
+	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
+	struct keembay_pcie *pcie = dev_get_drvdata(pci->dev);
+
+	writel(EDMA_INT_EN, pcie->apb_base + PCIE_REGS_INTERRUPT_ENABLE);
+}
+
+static int keembay_pcie_ep_raise_irq(struct dw_pcie_ep *ep, u8 func_no,
+				     enum pci_epc_irq_type type,
+				     u16 interrupt_num)
+{
+	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
+
+	switch (type) {
+	case PCI_EPC_IRQ_LEGACY:
+		/* Legacy interrupts are not supported in Keem Bay */
+		dev_err(pci->dev, "Legacy IRQ is not supported\n");
+		return -EINVAL;
+	case PCI_EPC_IRQ_MSI:
+		return dw_pcie_ep_raise_msi_irq(ep, func_no, interrupt_num);
+	case PCI_EPC_IRQ_MSIX:
+		return dw_pcie_ep_raise_msix_irq(ep, func_no, interrupt_num);
+	default:
+		dev_err(pci->dev, "Unknown IRQ type %d\n", type);
+		return -EINVAL;
+	}
+}
+
+static const struct pci_epc_features keembay_pcie_epc_features = {
+	.linkup_notifier	= false,
+	.msi_capable		= true,
+	.msix_capable		= true,
+	.reserved_bar		= BIT(BAR_1) | BIT(BAR_3) | BIT(BAR_5),
+	.bar_fixed_64bit	= BIT(BAR_0) | BIT(BAR_2) | BIT(BAR_4),
+	.align			= SZ_16K,
+};
+
+static const struct pci_epc_features *
+keembay_pcie_get_features(struct dw_pcie_ep *ep)
+{
+	return &keembay_pcie_epc_features;
+}
+
+static const struct dw_pcie_ep_ops keembay_pcie_ep_ops = {
+	.ep_init	= keembay_pcie_ep_init,
+	.raise_irq	= keembay_pcie_ep_raise_irq,
+	.get_features	= keembay_pcie_get_features,
+};
+
+static const struct dw_pcie_host_ops keembay_pcie_host_ops = {
+};
+
+static int keembay_pcie_add_pcie_port(struct keembay_pcie *pcie,
+				      struct platform_device *pdev)
+{
+	struct dw_pcie *pci = &pcie->pci;
+	struct pcie_port *pp = &pci->pp;
+	struct device *dev = &pdev->dev;
+	u32 val;
+	int ret;
+
+	pp->ops = &keembay_pcie_host_ops;
+	pp->msi_irq = -ENODEV;
+
+	ret = keembay_pcie_setup_msi_irq(pcie);
+	if (ret)
+		return ret;
+
+	pcie->reset = devm_gpiod_get(dev, "reset", GPIOD_OUT_HIGH);
+	if (IS_ERR(pcie->reset))
+		return PTR_ERR(pcie->reset);
+
+	ret = keembay_pcie_probe_clocks(pcie);
+	if (ret)
+		return ret;
+
+	val = readl(pcie->apb_base + PCIE_REGS_PCIE_PHY_CNTL);
+	val |= PHY0_SRAM_BYPASS;
+	writel(val, pcie->apb_base + PCIE_REGS_PCIE_PHY_CNTL);
+
+	writel(PCIE_DEVICE_TYPE, pcie->apb_base + PCIE_REGS_PCIE_CFG);
+
+	ret = keembay_pcie_pll_init(pcie);
+	if (ret)
+		return ret;
+
+	val = readl(pcie->apb_base + PCIE_REGS_PCIE_CFG);
+	writel(val | PCIE_RSTN, pcie->apb_base + PCIE_REGS_PCIE_CFG);
+	keembay_ep_reset_deassert(pcie);
+
+	ret = dw_pcie_host_init(pp);
+	if (ret) {
+		keembay_ep_reset_assert(pcie);
+		dev_err(dev, "Failed to initialize host: %d\n", ret);
+		return ret;
+	}
+
+	val = readl(pcie->apb_base + PCIE_REGS_INTERRUPT_ENABLE);
+	if (IS_ENABLED(CONFIG_PCI_MSI))
+		val |= MSI_CTRL_INT_EN;
+	writel(val, pcie->apb_base + PCIE_REGS_INTERRUPT_ENABLE);
+
+	return 0;
+}
+
+static int keembay_pcie_probe(struct platform_device *pdev)
+{
+	const struct keembay_pcie_of_data *data;
+	struct device *dev = &pdev->dev;
+	struct keembay_pcie *pcie;
+	struct dw_pcie *pci;
+	enum dw_pcie_device_mode mode;
+
+	data = device_get_match_data(dev);
+	if (!data)
+		return -ENODEV;
+
+	mode = (enum dw_pcie_device_mode)data->mode;
+
+	pcie = devm_kzalloc(dev, sizeof(*pcie), GFP_KERNEL);
+	if (!pcie)
+		return -ENOMEM;
+
+	pci = &pcie->pci;
+	pci->dev = dev;
+	pci->ops = &keembay_pcie_ops;
+
+	pcie->mode = mode;
+
+	pcie->apb_base = devm_platform_ioremap_resource_byname(pdev, "apb");
+	if (IS_ERR(pcie->apb_base))
+		return PTR_ERR(pcie->apb_base);
+
+	platform_set_drvdata(pdev, pcie);
+
+	switch (pcie->mode) {
+	case DW_PCIE_RC_TYPE:
+		if (!IS_ENABLED(CONFIG_PCIE_KEEMBAY_HOST))
+			return -ENODEV;
+
+		return keembay_pcie_add_pcie_port(pcie, pdev);
+	case DW_PCIE_EP_TYPE:
+		if (!IS_ENABLED(CONFIG_PCIE_KEEMBAY_EP))
+			return -ENODEV;
+
+		pci->ep.ops = &keembay_pcie_ep_ops;
+		return dw_pcie_ep_init(&pci->ep);
+	default:
+		dev_err(dev, "Invalid device type %d\n", pcie->mode);
+		return -ENODEV;
+	}
+}
+
+static const struct keembay_pcie_of_data keembay_pcie_rc_of_data = {
+	.mode = DW_PCIE_RC_TYPE,
+};
+
+static const struct keembay_pcie_of_data keembay_pcie_ep_of_data = {
+	.mode = DW_PCIE_EP_TYPE,
+};
+
+static const struct of_device_id keembay_pcie_of_match[] = {
+	{
+		.compatible = "intel,keembay-pcie",
+		.data = &keembay_pcie_rc_of_data,
+	},
+	{
+		.compatible = "intel,keembay-pcie-ep",
+		.data = &keembay_pcie_ep_of_data,
+	},
+	{}
+};
+
+static struct platform_driver keembay_pcie_driver = {
+	.driver = {
+		.name = "keembay-pcie",
+		.of_match_table = keembay_pcie_of_match,
+		.suppress_bind_attrs = true,
+	},
+	.probe  = keembay_pcie_probe,
+};
+builtin_platform_driver(keembay_pcie_driver);
--
2.17.1