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Date: Fri, 27 Nov 2015 15:17:36 +0000
From: Marc Zyngier <marc.zyngier@....com>
To: Ray Jui <rjui@...adcom.com>, Bjorn Helgaas <bhelgaas@...gle.com>
CC: Arnd Bergmann <arnd@...db.de>, Hauke Mehrtens <hauke@...ke-m.de>,
linux-kernel@...r.kernel.org,
bcm-kernel-feedback-list@...adcom.com, linux-pci@...r.kernel.org
Subject: Re: [PATCH v3 4/5] PCI: iproc: Add iProc PCIe MSI support
On 26/11/15 22:37, Ray Jui wrote:
> This patch adds PCIe MSI support for both PAXB and PAXC interfaces on
> all iProc based platforms
>
> The iProc PCIe MSI support deploys an event queue based implementation.
> Each event queue is serviced by a GIC interrupt and can support up to 64
> MSI vectors. Host memory is allocated for the event queues, and each event
> queue consists of 64 word-sized entries. MSI data is written to the
> lower 16-bit of each entry, whereas the upper 16-bit of the entry is
> reserved for the controller for internal processing
>
> Each event queue is tracked by a head pointer and tail pointer. Head
> pointer indicates the next entry in the event queue to be processed by
> the driver and is updated by the driver after processing is done.
> The controller uses the tail pointer as the next MSI data insertion
> point. The controller ensures MSI data is flushed to host memory before
> updating the tail pointer and then triggering the interrupt
>
> MSI IRQ affinity is supported by evenly distributing the interrupts to
> each CPU core. MSI vector is moved from one GIC interrupt to another in
> order to steer to the target CPU
>
> Therefore, the actual number of supported MSI vectors is:
>
> M * 64 / N
>
> where M denotes the number of GIC interrupts (event queues), and N
> denotes the number of CPU cores
>
> This iProc event queue based MSI support should not be used with newer
> platforms with integrated MSI support in the GIC (e.g., giv2m or
> gicv3-its)
>
> Signed-off-by: Ray Jui <rjui@...adcom.com>
> Reviewed-by: Anup Patel <anup.patel@...adcom.com>
> Reviewed-by: Vikram Prakash <vikramp@...adcom.com>
> Reviewed-by: Scott Branden <sbranden@...adcom.com>
> ---
> drivers/pci/host/Kconfig | 9 +
> drivers/pci/host/Makefile | 1 +
> drivers/pci/host/pcie-iproc-bcma.c | 1 +
> drivers/pci/host/pcie-iproc-msi.c | 678 +++++++++++++++++++++++++++++++++
> drivers/pci/host/pcie-iproc-platform.c | 1 +
> drivers/pci/host/pcie-iproc.c | 26 ++
> drivers/pci/host/pcie-iproc.h | 23 +-
> 7 files changed, 737 insertions(+), 2 deletions(-)
> create mode 100644 drivers/pci/host/pcie-iproc-msi.c
>
[...]
> diff --git a/drivers/pci/host/pcie-iproc-msi.c b/drivers/pci/host/pcie-iproc-msi.c
> new file mode 100644
> index 0000000..f64399a
> --- /dev/null
> +++ b/drivers/pci/host/pcie-iproc-msi.c
[...]
> +int iproc_msi_init(struct iproc_pcie *pcie, struct device_node *node)
> +{
> + struct iproc_msi *msi;
> + int i, ret;
> + unsigned int cpu;
> +
> + if (!of_device_is_compatible(node, "brcm,iproc-msi"))
> + return -ENODEV;
> +
> + if (!of_find_property(node, "msi-controller", NULL))
> + return -ENODEV;
> +
> + if (pcie->msi)
> + return -EBUSY;
> +
> + msi = devm_kzalloc(pcie->dev, sizeof(*msi), GFP_KERNEL);
> + if (!msi)
> + return -ENOMEM;
> +
> + msi->pcie = pcie;
> + pcie->msi = msi;
> + msi->msi_addr = pcie->base_addr;
> + mutex_init(&msi->bitmap_lock);
> + msi->nr_cpus = num_online_cpus();
What if some of the CPUs are offline at that time, but come back online
later? My guess is that you need to have num_possible_cpus().
> +
> + msi->nr_irqs = of_irq_count(node);
> + if (!msi->nr_irqs) {
> + dev_err(pcie->dev, "found no MSI GIC interrupt\n");
> + return -ENODEV;
> + }
> +
> + if (msi->nr_irqs > NR_HW_IRQS) {
> + dev_warn(pcie->dev, "too many MSI GIC interrupts defined %d\n",
> + msi->nr_irqs);
> + msi->nr_irqs = NR_HW_IRQS;
> + }
> +
> + if (msi->nr_irqs < msi->nr_cpus) {
> + dev_err(pcie->dev,
> + "not enough GIC interrupts for MSI affinity\n");
> + return -EINVAL;
> + }
> +
> + if (msi->nr_irqs % msi->nr_cpus != 0) {
> + msi->nr_irqs -= msi->nr_irqs % msi->nr_cpus;
> + dev_warn(pcie->dev, "Reducing number of interrupts to %d\n",
> + msi->nr_irqs);
> + }
> +
> + switch (pcie->type) {
> + case IPROC_PCIE_PAXB:
> + msi->reg_offsets = iproc_msi_reg_paxb;
> + msi->nr_eq_region = 1;
> + msi->nr_msi_region = 1;
> + break;
> + case IPROC_PCIE_PAXC:
> + msi->reg_offsets = iproc_msi_reg_paxc;
> + msi->nr_eq_region = msi->nr_irqs;
> + msi->nr_msi_region = msi->nr_irqs;
> + break;
> + default:
> + dev_err(pcie->dev, "incompatible iProc PCIe interface\n");
> + return -EINVAL;
> + }
> +
> + if (of_find_property(node, "brcm,pcie-msi-inten", NULL))
> + msi->has_inten_reg = true;
> +
> + msi->nr_msi_vecs = msi->nr_irqs * EQ_LEN;
> + msi->bitmap = devm_kcalloc(pcie->dev, BITS_TO_LONGS(msi->nr_msi_vecs),
> + sizeof(*msi->bitmap), GFP_KERNEL);
> + if (!msi->bitmap)
> + return -ENOMEM;
> +
> + msi->grps = devm_kcalloc(pcie->dev, msi->nr_irqs, sizeof(*msi->grps),
> + GFP_KERNEL);
> + if (!msi->grps)
> + return -ENOMEM;
> +
> + for (i = 0; i < msi->nr_irqs; i++) {
> + unsigned int irq = irq_of_parse_and_map(node, i);
> +
> + if (!irq) {
> + dev_err(pcie->dev, "unable to parse/map interrupt\n");
> + ret = -ENODEV;
> + goto free_irqs;
> + }
> + msi->grps[i].gic_irq = irq;
> + msi->grps[i].msi = msi;
> + msi->grps[i].eq = i;
> + }
> +
> + /* reserve memory for MSI event queue */
> + msi->eq_cpu = dma_alloc_coherent(pcie->dev,
> + msi->nr_eq_region * EQ_MEM_REGION_SIZE,
> + &msi->eq_dma, GFP_KERNEL);
> + if (!msi->eq_cpu) {
> + ret = -ENOMEM;
> + goto free_irqs;
> + }
> +
> + /* zero out all memory contents of the MSI event queues */
> + memset(msi->eq_cpu, 0, msi->nr_eq_region * EQ_MEM_REGION_SIZE);
> +
Please use dma_zalloc_coherent instead of memsetting the memory.
Thanks,
M.
--
Jazz is not dead. It just smells funny...
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