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    SubjectRe: [RFC PATCH 1/2] irqchip: cdx-bus: add cdx-MSI domain with gic-its domain as parent
    On Wed, 03 Aug 2022 13:26:54 +0100,
    Nipun Gupta <nipun.gupta@amd.com> wrote:
    >
    > Devices on cdx bus are dynamically detected and registered using
    > platform_device_register API. As these devices are not linked to
    > of node they need a separate MSI domain for handling device ID
    > to be provided to the GIC ITS domain.
    >
    > Signed-off-by: Nipun Gupta <nipun.gupta@amd.com>
    > Signed-off-by: Nikhil Agarwal <nikhil.agarwal@amd.com>
    > ---
    > CONFIG_CDX_BUS and device tree bindings for xlnx,cdx-controller-1.0
    > would be added as part of CDX bus patches
    >
    > drivers/irqchip/Makefile | 1 +
    > drivers/irqchip/irq-gic-v3-its-cdx-msi.c | 113 +++++++++++++++++++++++
    > include/linux/cdx/cdx.h | 15 +++
    > 3 files changed, 129 insertions(+)
    > create mode 100644 drivers/irqchip/irq-gic-v3-its-cdx-msi.c
    > create mode 100644 include/linux/cdx/cdx.h
    >
    > diff --git a/drivers/irqchip/Makefile b/drivers/irqchip/Makefile
    > index 5b67450a9538..623adb8a1f20 100644
    > --- a/drivers/irqchip/Makefile
    > +++ b/drivers/irqchip/Makefile
    > @@ -115,3 +115,4 @@ obj-$(CONFIG_WPCM450_AIC) += irq-wpcm450-aic.o
    > obj-$(CONFIG_IRQ_IDT3243X) += irq-idt3243x.o
    > obj-$(CONFIG_APPLE_AIC) += irq-apple-aic.o
    > obj-$(CONFIG_MCHP_EIC) += irq-mchp-eic.o
    > +obj-$(CONFIG_CDX_BUS) += irq-gic-v3-its-cdx-msi.o
    > diff --git a/drivers/irqchip/irq-gic-v3-its-cdx-msi.c b/drivers/irqchip/irq-gic-v3-its-cdx-msi.c
    > new file mode 100644
    > index 000000000000..eb17b74efdc5
    > --- /dev/null
    > +++ b/drivers/irqchip/irq-gic-v3-its-cdx-msi.c
    > @@ -0,0 +1,113 @@
    > +// SPDX-License-Identifier: GPL-2.0
    > +/*
    > + * AMD CDX bus driver MSI support
    > + *
    > + * Copyright(C) 2022 Xilinx Inc.
    > + */
    > +
    > +#include <linux/irq.h>
    > +#include <linux/msi.h>
    > +#include <linux/of.h>
    > +#include <linux/of_address.h>
    > +#include <linux/of_device.h>
    > +#include <linux/of_irq.h>
    > +#include <linux/cdx/cdx.h>
    > +
    > +static struct irq_chip its_msi_irq_chip = {
    > + .name = "ITS-fMSI",
    > + .irq_mask = irq_chip_mask_parent,
    > + .irq_unmask = irq_chip_unmask_parent,
    > + .irq_eoi = irq_chip_eoi_parent,
    > + .irq_set_affinity = msi_domain_set_affinity
    > +};
    > +
    > +static int its_cdx_msi_prepare(struct irq_domain *msi_domain,
    > + struct device *dev,
    > + int nvec, msi_alloc_info_t *info)
    > +{
    > + struct msi_domain_info *msi_info;
    > + struct cdx_device_data *dev_data;
    > + u32 dev_id;
    > +
    > + dev_data = dev->platform_data;
    > + dev_id = dev_data->dev_id;
    > +
    > + /* Set the device Id to be passed to the GIC-ITS */
    > + info->scratchpad[0].ul = dev_id;
    > +
    > + msi_info = msi_get_domain_info(msi_domain->parent);
    > +
    > + /* Allocate at least 32 MSIs, and always as a power of 2 */
    > + nvec = max_t(int, 32, roundup_pow_of_two(nvec));
    > + return msi_info->ops->msi_prepare(msi_domain->parent, dev, nvec, info);
    > +}
    > +
    > +static struct msi_domain_ops its_cdx_msi_ops __ro_after_init = {
    > + .msi_prepare = its_cdx_msi_prepare,
    > +};
    > +
    > +static struct msi_domain_info its_cdx_msi_domain_info = {
    > + .flags = (MSI_FLAG_USE_DEF_DOM_OPS | MSI_FLAG_USE_DEF_CHIP_OPS),
    > + .ops = &its_cdx_msi_ops,
    > + .chip = &its_msi_irq_chip,
    > +};
    > +
    > +static const struct of_device_id cdx_device_id[] = {
    > + {.compatible = "xlnx,cdx-controller-1.0", },

    What is this? If this is supposed to represent am ITS, it really
    should say so.

    > + {},
    > +};
    > +
    > +struct irq_domain *get_parent(struct fwnode_handle *handle)
    > +{
    > + return irq_find_matching_fwnode(handle, DOMAIN_BUS_NEXUS);
    > +}
    > +
    > +static void __init its_cdx_msi_init_one(struct device_node *np,
    > + const char *name)
    > +{
    > + struct irq_domain *parent;
    > + struct irq_domain *cdx_msi_domain;
    > + struct fwnode_handle *fwnode_handle;
    > + struct device_node *parent_node;
    > +
    > + parent_node = of_parse_phandle(np, "msi-parent", 0);
    > +
    > + parent = get_parent(of_node_to_fwnode(parent_node));
    > + if (!parent || !msi_get_domain_info(parent)) {
    > + pr_err("%s: unable to locate ITS domain\n", name);
    > + return;
    > + }
    > +
    > + fwnode_handle = of_node_to_fwnode(np);
    > + cdx_msi_domain = platform_msi_create_irq_domain(fwnode_handle,
    > + &its_cdx_msi_domain_info,
    > + parent);
    > + if (!cdx_msi_domain) {
    > + pr_err("%s: unable to create cdx bus domain\n", name);
    > + return;
    > + }
    > +
    > + pr_info("cdx bus MSI: %s domain created\n", name);
    > +}
    > +
    > +static void __init its_cdx_of_msi_init(void)
    > +{
    > + struct device_node *np;
    > +
    > + for (np = of_find_matching_node(NULL, cdx_device_id); np;
    > + np = of_find_matching_node(np, cdx_device_id)) {
    > + if (!of_device_is_available(np))
    > + continue;
    > +
    > + its_cdx_msi_init_one(np, np->full_name);
    > + }
    > +}
    > +
    > +static int __init its_cdx_msi_init(void)
    > +{
    > + its_cdx_of_msi_init();
    > +
    > + return 0;
    > +}
    > +
    > +early_initcall(its_cdx_msi_init);

    I really don't think we should have any more of this muck. Yes, the
    other busses are also doing that, but here's our chance to do
    something better.

    Why can't the *bus* driver (I assume there is one) perform these
    tasks? It would really help if this patch was shown in context,
    because I have no idea how this fits in the grand scheme of things.

    Thanks,

    M.

    --
    Without deviation from the norm, progress is not possible.

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