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

[Thierry Reding <thierry.reding-RM9K5IK7kjKj5M59NBduVrNAH6kLmebB@public.gmane.org>]

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* Stephen Warren wrote:
> On 03/08/2012 07:51 AM, Thierry Reding wrote:
> > This commit adds support for message signaled interrupts to the Tegra
> > PCIe controller.
> > 
> > Signed-off-by: Thierry Reding <thierry.reding-RM9K5IK7kjKj5M59NBduVrNAH6kLmebB@public.gmane.org>
> > ---
> > 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 <kthota-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>" 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

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

> > +		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.

> > +		return err;
> > +	}
> ...
> 
> > +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

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