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SubjectRe: [PATCH V3 10/10] acpi, gicv3, its: Use MADT ITS subtable to do PCI/MSI domain initialization.
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On 19/01/16 13:11, Tomasz Nowicki wrote:
> After refactoring DT code, we let ACPI to build ITS PCI MSI domain
> and do requester ID to device ID translation using IORT table.
>
> We have now full PCI MSI domain stack, thus we can enable ITS initialization
> from GICv3 core driver for ACPI scenario.
>
> Signed-off-by: Tomasz Nowicki <tn@semihalf.com>
> ---
> drivers/irqchip/irq-gic-v3-its-pci-msi.c | 44 +++++++++++++++++++++++++++++++-
> drivers/irqchip/irq-gic-v3.c | 3 +--
> drivers/pci/msi.c | 3 +++
> 3 files changed, 47 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/irqchip/irq-gic-v3-its-pci-msi.c b/drivers/irqchip/irq-gic-v3-its-pci-msi.c
> index 06165cb..7f0a958 100644
> --- a/drivers/irqchip/irq-gic-v3-its-pci-msi.c
> +++ b/drivers/irqchip/irq-gic-v3-its-pci-msi.c
> @@ -15,6 +15,8 @@
> * along with this program. If not, see <http://www.gnu.org/licenses/>.
> */
>
> +#include <linux/acpi.h>
> +#include <linux/iort.h>
> #include <linux/msi.h>
> #include <linux/of.h>
> #include <linux/of_irq.h>
> @@ -143,10 +145,50 @@ static int __init its_pci_of_msi_init(void)
> return 0;
> }
>
> +#ifdef CONFIG_ACPI
> +
> +static int __init
> +its_pci_msi_parse_madt(struct acpi_subtable_header *header,
> + const unsigned long end)
> +{
> + struct acpi_madt_generic_translator *its_entry;
> + struct fwnode_handle *domain_handle;
> +
> + its_entry = (struct acpi_madt_generic_translator *)header;
> + domain_handle = iort_find_its_domain_token(its_entry->translation_id);
> + if (!domain_handle) {
> + pr_err("ITS@0x%lx: Unable to locate ITS domain handle\n",
> + (long)its_entry->base_address);
> + return 0;
> + }
> +
> + if (its_pci_msi_init_one(domain_handle))
> + return 0;
> +
> + pci_msi_register_fwnode_provider(&iort_find_pci_domain_token);

I'm a bit worried by this. You are registering this for each and every
ITS that gets probed (useless, but why not). But also, you're using a
hook that is designed to work at the bus level, without caring for the
actual PCI devices. That's fine for something like GICv2m, which exposes
a single domain, but I can't picture how this works when you have
devices sitting behind a single RC that talk to different ITSs.

My understanding is that IORT was behaving in a similar way the msi-map
property works, so I'm a bit puzzled here.

Can you please shed some light on that?

Thanks,

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

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