Re: [PATCH v5 3/5] pci: altera: Add Altera PCIe MSI driver

[Marc Zyngier]

On 25/08/15 10:35, Ley Foon Tan wrote:
> This patch adds Altera PCIe MSI driver. This soft IP supports configurable
> number of vectors, which is a dts parameter.
> 
> Signed-off-by: Ley Foon Tan <lftan@xxxxxxxxxx>
> ---
>  drivers/pci/host/Kconfig           |   8 +
>  drivers/pci/host/Makefile          |   1 +
>  drivers/pci/host/pcie-altera-msi.c | 322 +++++++++++++++++++++++++++++++++++++
>  3 files changed, 331 insertions(+)
>  create mode 100644 drivers/pci/host/pcie-altera-msi.c
> 
> diff --git a/drivers/pci/host/Kconfig b/drivers/pci/host/Kconfig
> index 4b4754a..d28cc6d 100644
> --- a/drivers/pci/host/Kconfig
> +++ b/drivers/pci/host/Kconfig
> @@ -152,4 +152,12 @@ config PCIE_ALTERA
>  	  Say Y here if you want to enable PCIe controller support for Altera
>  	  SoCFPGA family of SoCs.
>  
> +config PCIE_ALTERA_MSI
> +	bool "Altera PCIe MSI feature"
> +	depends on PCI_MSI
> +	select PCI_MSI_IRQ_DOMAIN
> +	help
> +	  Say Y here if you want PCIe MSI support for the Altera SocFPGA SoC.
> +	  This MSI driver supports Altera MSI to GIC controller IP.
> +
>  endmenu
> diff --git a/drivers/pci/host/Makefile b/drivers/pci/host/Makefile
> index 6954f76..6c4913d 100644
> --- a/drivers/pci/host/Makefile
> +++ b/drivers/pci/host/Makefile
> @@ -18,3 +18,4 @@ obj-$(CONFIG_PCIE_IPROC) += pcie-iproc.o
>  obj-$(CONFIG_PCIE_IPROC_PLATFORM) += pcie-iproc-platform.o
>  obj-$(CONFIG_PCIE_IPROC_BCMA) += pcie-iproc-bcma.o
>  obj-$(CONFIG_PCIE_ALTERA) += pcie-altera.o
> +obj-$(CONFIG_PCIE_ALTERA_MSI) += pcie-altera-msi.o
> diff --git a/drivers/pci/host/pcie-altera-msi.c b/drivers/pci/host/pcie-altera-msi.c
> new file mode 100644
> index 0000000..d3ad96f
> --- /dev/null
> +++ b/drivers/pci/host/pcie-altera-msi.c
> @@ -0,0 +1,322 @@
> +/*
> + * Copyright Altera Corporation (C) 2013-2015. All rights reserved
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> + * more details.
> + *
> + * You should have received a copy of the GNU General Public License along with
> + * this program.  If not, see <http://www.gnu.org/licenses/>.
> + */
> +#include <linux/interrupt.h>
> +#include <linux/irqchip/chained_irq.h>
> +#include <linux/module.h>
> +#include <linux/msi.h>
> +#include <linux/of_address.h>
> +#include <linux/of_irq.h>
> +#include <linux/of_pci.h>
> +#include <linux/pci.h>
> +#include <linux/platform_device.h>
> +#include <linux/slab.h>
> +
> +#define MSI_STATUS		0x0
> +#define MSI_ERROR		0x4
> +#define MSI_INTMASK		0x8
> +
> +#define MAX_MSI_VECTORS		32
> +struct altera_msi {
> +	DECLARE_BITMAP(used, MAX_MSI_VECTORS);
> +	struct mutex		lock;	/* proctect used variable */
> +	struct platform_device	*pdev;
> +	struct irq_domain		*msi_domain;
> +	struct irq_domain		*inner_domain;
> +	void __iomem		*csr_base;
> +	void __iomem		*vector_base;
> +	phys_addr_t		vector_phy;
> +	u32			num_of_vectors;
> +	int			irq;
> +};
> +
> +static inline void msi_writel(struct altera_msi *msi, u32 value, u32 reg)
> +{
> +	writel_relaxed(value, msi->csr_base + reg);
> +}
> +
> +static inline u32 msi_readl(struct altera_msi *msi, u32 reg)
> +{
> +	return readl_relaxed(msi->csr_base + reg);
> +}
> +
> +static void altera_msi_isr(unsigned int irq, struct irq_desc *desc)
> +{
> +	struct irq_chip *chip = irq_desc_get_chip(desc);
> +	struct altera_msi *msi;
> +	unsigned long status;
> +	u32 num_of_vectors;
> +	u32 bit;
> +	u32 virq;
> +
> +	chained_irq_enter(chip, desc);
> +	msi = irq_desc_get_handler_data(desc);
> +	num_of_vectors = msi->num_of_vectors;
> +
> +	do {
> +		status = msi_readl(msi, MSI_STATUS);
> +		if (!status)
> +			break;
> +
> +		do {
> +			bit = find_first_bit(&status, num_of_vectors);
> +			/* Dummy read from vector to clear the interrupt */
> +			readl_relaxed(msi->vector_base + (bit * sizeof(u32)));
> +
> +			virq = irq_find_mapping(msi->inner_domain, bit);
> +			if (virq && test_bit(bit, msi->used))

I still wonder under which circumstances you can obtain a valid virq and
yet not find the bit in the bitmap. Unless you have a scenario when that
can happen, I suggest you remove that test.

> +				generic_handle_irq(virq);
> +			else
> +				dev_err(&msi->pdev->dev, "unexpected MSI\n");
> +
> +			/* Clear the bit from status and repeat without reading
> +			 * again status register. */
> +			__clear_bit(bit, &status);
> +		} while (status);
> +	} while (1);

I think this could be rewritten as:

while ((status = msi_readl(msi, MSI_STATUS)) != 0) {
	for_each_set_bit(bit, &status, msi->num_of_vectors) {
		/* Dummy read from vector to clear the interrupt */
		readl_relaxed(msi->vector_base + (bit * sizeof(u32)));

		virq = irq_find_mapping(msi->inner_domain, bit);
		if (virq)
			generic_handle_irq(virq);
		else
			dev_err(&msi->pdev->dev, "unexpected MSI\n");
	}
}

which saves the __clear_bit call and the double test of status which I
find a bit awkward.

> +
> +	chained_irq_exit(chip, desc);
> +}
> +
> +static struct irq_chip altera_msi_irq_chip = {
> +	.name = "Altera PCIe MSI",
> +	.irq_enable = pci_msi_unmask_irq,
> +	.irq_disable = pci_msi_mask_irq,
> +	.irq_mask = pci_msi_mask_irq,
> +	.irq_unmask = pci_msi_unmask_irq,

Why do you have both enable/disable and unmask/mask? Specially pointing
to the same function? This is completely useless. Just stick with
unmask/mask and remove the enable/disable.

> +};
> +
> +static struct msi_domain_info altera_msi_domain_info = {
> +	.flags	= (MSI_FLAG_USE_DEF_DOM_OPS | MSI_FLAG_USE_DEF_CHIP_OPS |
> +		     MSI_FLAG_PCI_MSIX),
> +	.chip	= &altera_msi_irq_chip,
> +};
> +
> +static void altera_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
> +{
> +	struct altera_msi *msi = irq_data_get_irq_chip_data(data);
> +	phys_addr_t addr = msi->vector_phy + (data->hwirq * sizeof(u32));
> +
> +	msg->address_lo = lower_32_bits(addr);
> +	msg->address_hi = upper_32_bits(addr);
> +	msg->data = data->hwirq;
> +
> +	dev_dbg(&msi->pdev->dev, "msi#%d address_lo 0x%x address_hi 0x%x\n",
> +		(int)data->hwirq, msg->address_hi, msg->address_lo);
> +}
> +
> +static int altera_msi_set_affinity(struct irq_data *irq_data,
> +				   const struct cpumask *mask, bool force)
> +{
> +	 return -EINVAL;
> +}
> +
> +static struct irq_chip altera_msi_bottom_irq_chip = {
> +	.name			= "Altera MSI",
> +	.irq_compose_msi_msg	= altera_compose_msi_msg,
> +	.irq_set_affinity	= altera_msi_set_affinity,
> +};
> +
> +static int altera_irq_domain_alloc(struct irq_domain *domain, unsigned int virq,
> +				   unsigned int nr_irqs, void *args)
> +{
> +	struct altera_msi *msi = domain->host_data;
> +	unsigned long bit;
> +	u32 mask;
> +
> +	WARN_ON(nr_irqs != 1);
> +	mutex_lock(&msi->lock);
> +
> +	bit = find_first_zero_bit(msi->used, msi->num_of_vectors);
> +	if (bit >= msi->num_of_vectors)
> +		return -ENOSPC;
> +
> +	set_bit(bit, msi->used);
> +
> +	mutex_unlock(&msi->lock);
> +
> +	irq_domain_set_info(domain, virq, bit, &altera_msi_bottom_irq_chip,
> +			    domain->host_data, handle_simple_irq,
> +			    NULL, NULL);
> +	set_irq_flags(virq, IRQF_VALID);
> +
> +	mask = msi_readl(msi, MSI_INTMASK);
> +	mask |= 1 << bit;
> +	msi_writel(msi, mask, MSI_INTMASK);
> +
> +	return 0;
> +}
> +
> +static void altera_irq_domain_free(struct irq_domain *domain,
> +				   unsigned int virq, unsigned int nr_irqs)
> +{
> +	struct irq_data *d = irq_domain_get_irq_data(domain, virq);
> +	struct altera_msi *msi = irq_data_get_irq_chip_data(d);
> +	u32 mask;
> +
> +	mutex_lock(&msi->lock);
> +
> +	if (!test_bit(d->hwirq, msi->used)) {
> +		dev_err(&msi->pdev->dev, "trying to free unused MSI#%lu\n",
> +			d->hwirq);
> +	} else {
> +		__clear_bit(d->hwirq, msi->used);
> +		mask = msi_readl(msi, MSI_INTMASK);
> +		mask &= ~(1 << d->hwirq);
> +		msi_writel(msi, mask, MSI_INTMASK);
> +	}
> +
> +	mutex_unlock(&msi->lock);
> +}
> +
> +static const struct irq_domain_ops msi_domain_ops = {
> +	.alloc	= altera_irq_domain_alloc,
> +	.free	= altera_irq_domain_free,
> +};
> +
> +static int altera_allocate_domains(struct altera_msi *msi)
> +{
> +	msi->inner_domain = irq_domain_add_linear(NULL, msi->num_of_vectors,
> +					     &msi_domain_ops, msi);
> +	if (!msi->inner_domain) {
> +		dev_err(&msi->pdev->dev, "failed to create IRQ domain\n");
> +		return -ENOMEM;
> +	}
> +
> +	msi->msi_domain = pci_msi_create_irq_domain(msi->pdev->dev.of_node,
> +				&altera_msi_domain_info, msi->inner_domain);
> +	if (!msi->msi_domain) {
> +		dev_err(&msi->pdev->dev, "failed to create MSI domain\n");
> +		irq_domain_remove(msi->inner_domain);
> +		return -ENOMEM;
> +	}
> +
> +	return 0;
> +}
> +
> +static void altera_free_domains(struct altera_msi *msi)
> +{
> +	irq_domain_remove(msi->msi_domain);
> +	irq_domain_remove(msi->inner_domain);
> +}
> +
> +static int altera_msi_remove(struct platform_device *pdev)
> +{
> +	struct altera_msi *msi = platform_get_drvdata(pdev);
> +
> +	msi_writel(msi, 0, MSI_INTMASK);
> +	irq_set_chained_handler(msi->irq, NULL);
> +	irq_set_handler_data(msi->irq, NULL);
> +
> +	altera_free_domains(msi);
> +
> +	platform_set_drvdata(pdev, NULL);
> +	return 0;
> +}
> +
> +static int altera_msi_probe(struct platform_device *pdev)
> +{
> +	struct altera_msi *msi;
> +	struct device_node *np = pdev->dev.of_node;
> +	struct resource *res;
> +	int ret;
> +
> +	msi = devm_kzalloc(&pdev->dev, sizeof(struct altera_msi),
> +			   GFP_KERNEL);
> +	if (!msi)
> +		return -ENOMEM;
> +
> +	mutex_init(&msi->lock);
> +	msi->pdev = pdev;
> +
> +	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "csr");
> +	if (!res) {
> +		dev_err(&pdev->dev,
> +			"no csr memory resource defined\n");
> +		return -ENODEV;
> +	}
> +
> +	msi->csr_base = devm_ioremap_resource(&pdev->dev, res);
> +	if (IS_ERR(msi->csr_base)) {
> +		dev_err(&pdev->dev, "failed to map csr memory\n");
> +		return PTR_ERR(msi->csr_base);
> +	}
> +
> +	res = platform_get_resource_byname(pdev, IORESOURCE_MEM,
> +					   "vector_slave");
> +	if (!res) {
> +		dev_err(&pdev->dev,
> +			"no vector_slave memory resource defined\n");
> +		return -ENODEV;
> +	}
> +
> +	msi->vector_base = devm_ioremap_resource(&pdev->dev, res);
> +	if (IS_ERR(msi->vector_base)) {
> +		dev_err(&pdev->dev, "failed to map vector_slave memory\n");
> +		return PTR_ERR(msi->vector_base);
> +	}
> +
> +	msi->vector_phy = res->start;
> +
> +	if (of_property_read_u32(np, "num-vectors", &msi->num_of_vectors)) {
> +		dev_err(&pdev->dev, "failed to parse the number of vectors\n");
> +		return -EINVAL;
> +	}
> +
> +	ret = altera_allocate_domains(msi);
> +	if (ret)
> +		return ret;
> +
> +	msi->irq = platform_get_irq(pdev, 0);
> +	if (msi->irq <= 0) {
> +		dev_err(&pdev->dev, "failed to map IRQ: %d\n", msi->irq);
> +		ret = -ENODEV;
> +		goto err;
> +	}
> +
> +	irq_set_chained_handler_and_data(msi->irq, altera_msi_isr, msi);
> +	platform_set_drvdata(pdev, msi);
> +
> +	return 0;
> +
> +err:
> +	altera_msi_remove(pdev);
> +	return ret;
> +}
> +
> +static const struct of_device_id altera_msi_of_match[] = {
> +	{ .compatible = "altr,msi-1.0", NULL },
> +	{ },
> +};
> +
> +static struct platform_driver altera_msi_driver = {
> +	.driver = {
> +		.name = "altera-msi",
> +		.of_match_table = altera_msi_of_match,
> +	},
> +	.probe = altera_msi_probe,
> +	.remove = altera_msi_remove,
> +};
> +
> +static int __init altera_msi_init(void)
> +{
> +	return platform_driver_register(&altera_msi_driver);
> +}
> +
> +subsys_initcall(altera_msi_init);
> +
> +MODULE_AUTHOR("Ley Foon Tan <lftan@xxxxxxxxxx>");
> +MODULE_DESCRIPTION("Altera PCIe MSI support");
> +MODULE_LICENSE("GPL v2");
> 

Once you've fixed the above issues, you can add my:

Reviewed-by: Marc Zyngier <marc.zyngier@xxxxxxx>

	M.
-- 
Jazz is not dead. It just smells funny...
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