Re: [PATCH 10/11] ARM: tegra: pcie: Add MSI support

* Stephen Warren wrote:

On 03/08/2012 07:51 AM, Thierry Reding wrote:

quoted

This commit adds support for message signaled interrupts to the Tegra
PCIe controller.

Signed-off-by: Thierry Reding <redacted>
---
This code is taken from the NVIDIA Vibrante kernel and therefore has no
appropriate Signed-off-by from the original author. Maybe someone at
NVIDIA can find out who wrote this code and maybe provide a proper
Signed-off-by that I can add?

I think if you look in:
git://nv-tegra.nvidia.com/linux-2.6.git android-tegra-2.6.36

the following commits are what you're after:

de7fd8768b32da66eaf4eaf58473c65f7a76808d
arm: tegra: pcie: enabling MSI support for pcie

ac1f8310811c64a084511d2afc27f66334b31a81
ARM: tegra: pcie: fix return value from MSI irq routine

Although the patch below only partially resembles those patches, I guess
because you've rewritten the code a lot to conform to the current kernel
APIs, clean stuff up, etc. Perhaps just saying "based on code by Krishna
Kishore [off-list ref]" is enough...

Yes, it is indeed a major rewrite because the original code had some
peculiarities and FIXME that I thought wouldn't make it through the review
anyway so I fixed them up.

I'll add some comment about the original authorship. There is no official
Signed-off-by in the original commit. Do I still need one or is it enough to
mention the original authors in the commit message and add keep my own
Signed-off-by?

Thierry

quoted

diff --git a/arch/arm/mach-tegra/pcie.c b/arch/arm/mach-tegra/pcie.c

quoted

+static int tegra_pcie_enable_msi(struct platform_device *pdev)
+{
+	struct tegra_pcie_info *pcie = platform_get_drvdata(pdev);
+	volatile void *pages;
+	unsigned long base;
+	unsigned int msi;
+	int msi_base;
+	int err;
+	u32 reg;
+
+	mutex_init(&pcie->msi_lock);
+
+	msi_base = irq_alloc_descs(-1, 0, INT_PCI_MSI_NR, 0);
+	if (msi_base < 0) {
+		dev_err(&pdev->dev, "failed to allocate IRQs\n");
+		return msi_base;
+	}
+
+	pcie->msi_domain = irq_domain_add_legacy(pcie->dev->of_node,
+						 INT_PCI_MSI_NR, msi_base,
+						 0, &irq_domain_simple_ops,
+						 NULL);
+	if (!pcie->msi_domain) {
+		dev_err(&pdev->dev, "failed to create IRQ domain\n");

Free the IRQ descriptors in the error paths?

Yes, that would make sense.

quoted

+		return -ENOMEM;
+	}
+
+	pcie->msi_chip.name = "PCIe-MSI";
+	pcie->msi_chip.irq_enable = unmask_msi_irq;
+	pcie->msi_chip.irq_disable = mask_msi_irq;
+	pcie->msi_chip.irq_mask = mask_msi_irq;
+	pcie->msi_chip.irq_unmask = unmask_msi_irq;
+
+	for (msi = 0; msi < INT_PCI_MSI_NR; msi++) {
+		unsigned int irq = irq_find_mapping(pcie->msi_domain, msi);
+
+		irq_set_chip_data(irq, pcie);
+		irq_set_chip_and_handler(irq, &pcie->msi_chip,
+					 handle_simple_irq);
+		set_irq_flags(irq, IRQF_VALID);
+	}
+
+	err = platform_get_irq(pdev, 1);
+	if (err < 0) {
+		dev_err(&pdev->dev, "failed to get IRQ: %d\n", err);

Same here, and undo setting IRQF_VALID?

Right. I assume it would be best to also free the struct irq_domain and set
the chip data and handler back to NULL? AFAICT there is no canonical way to
teardown an irq_domain.

quoted

+		return err;
+	}

...

quoted

+static int tegra_pcie_disable_msi(struct platform_device *pdev)
+{
+	return 0;
+}

This is empty in both the ifdef(CONFIG_PCI_MSI) case and otherwise. It
should probably clean everything up here right?

Yes, initially this contained a call to free_irq(), which I removed when I
switched to using a chained handler. I can probably put all of the cleanup
code from your comments above in here and perhaps even call that in the error
paths of tegra_pcie_enable_msi().

Thierry