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Date: Fri, 27 Nov 2015 07:57:37 -0800
From: Ray Jui <rjui@...adcom.com>
To: Marc Zyngier <marc.zyngier@....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
Hi Marc,
On 11/27/2015 7:17 AM, Marc Zyngier wrote:
> 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().
>
Okay let me change this back to 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.
Definitely. Will do.
>
> Thanks,
>
> M.
>
Thanks, Marc!
Ray
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