Re: [RFC PATCH v4 7/8] bus/cdx: add cdx-MSI domain with gic-its domain as parent

[Thomas Gleixner]

On Fri, Oct 14 2022 at 10:10, Nipun Gupta wrote:
> Since CDX 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.
>
> This also introduces APIs to alloc and free IRQs for CDX domain.

This is not really much of an explanation.

> +#include "cdx.h"
> +
> +#define REQ_ID_SHIFT	10
> +
> +/*
> + * Convert an msi_desc to a globaly unique identifier (per-device
> + * reqid + msi_desc position in the msi_list).
> + */
> +static irq_hw_number_t cdx_domain_calc_hwirq(struct cdx_device *dev,
> +					     struct msi_desc *desc)
> +{
> +	return (dev->req_id << REQ_ID_SHIFT) | desc->msi_index;
> +}
> +
> +static void cdx_msi_set_desc(msi_alloc_info_t *arg,
> +			     struct msi_desc *desc)
> +{
> +	arg->desc = desc;
> +	arg->hwirq = cdx_domain_calc_hwirq(to_cdx_device(desc->dev), desc);
> +}
> +
> +static void cdx_msi_write_msg(struct irq_data *irq_data,
> +			      struct msi_msg *msg)
> +{
> +	struct msi_desc *msi_desc = irq_data_get_msi_desc(irq_data);
> +	struct cdx_device *cdx_dev = to_cdx_device(msi_desc->dev);
> +	struct cdx_controller_t *cdx = cdx_dev->cdx;
> +	uint64_t addr;
> +	int ret;
> +
> +	addr = ((uint64_t)(msi_desc->msg.address_hi) << 32) |
> +	       msi_desc->msg.address_lo;
> +
> +	ret = cdx->ops.write_msi(cdx, cdx_dev->bus_num, cdx_dev->dev_num,
> +				 msi_desc->msi_index, msi_desc->msg.data,
> +				 addr);
> +	if (ret)
> +		dev_err(&cdx_dev->dev, "Write MSI failed to CDX controller\n");
> +}

So this is yet another variant of platform-MSI which is about to be
kicked from the planet.

Please check:

     https://lore.kernel.org/r/20221111131813.914374272@xxxxxxxxxxxxx
     https://lore.kernel.org/r/20221111133158.196269823@xxxxxxxxxxxxx

and the ARM/GIC conversion in:

     https://git.kernel.org/pub/scm/linux/kernel/git/tglx/devel.git/log/?h=devmsi-arm

The latter is WIP, but functional.

I'm sure you replace your yet another magic MSI domain which only
provides a device specific MSI write function with the new
infrastructure trivially.

Thanks,

        tglx