Re: [PATCH v2 0/5] Add RC-to-EP doorbell with platform MSI controller

From: Niklas Cassel
Date: Wed Oct 09 2024 - 12:19:21 EST


On Mon, Sep 11, 2023 at 06:09:15PM -0400, Frank Li wrote:
> ┌────────────┐ ┌───────────────────────────────────┐ ┌────────────────┐
> │ │ │ │ │ │
> │ │ │ PCI Endpoint │ │ PCI Host │
> │ │ │ │ │ │
> │ │◄──┤ 1.platform_msi_domain_alloc_irqs()│ │ │
> │ │ │ │ │ │
> │ MSI ├──►│ 2.write_msi_msg() ├──►├─BAR<n> │
> │ Controller │ │ update doorbell register address│ │ │
> │ │ │ for BAR │ │ │
> │ │ │ │ │ 3. Write BAR<n>│
> │ │◄──┼───────────────────────────────────┼───┤ │
> │ │ │ │ │ │
> │ ├──►│ 4.Irq Handle │ │ │
> │ │ │ │ │ │
> │ │ │ │ │ │
> └────────────┘ └───────────────────────────────────┘ └────────────────┘
>
> This patches based on old https://lore.kernel.org/imx/20221124055036.1630573-1-Frank.Li@xxxxxxx/
>
> Original patch only target to vntb driver. But actually it is common
> method.
>
> This patches add new API to pci-epf-core, so any EP driver can use it.
>
> The key point is comments from Thomas Gleixner, who suggest use new
> PCI/IMS. But arm platform change still not be merged yet.
>
> git://git.kernel.org/pub/scm/linux/kernel/git/tglx/devel.git devmsi-v2-arm
>
> So I still use existed method implement RC to EP doorbell.
>
> If Thomas Gleixner want to continue work on devmsi-v2-arm, I can help test
> and update this patch.
>
> Change from v1 to v2
> - Add missed patch for endpont/pci-epf-test.c
> - Move alloc and free to epc driver from epf.
> - Provide general help function for EPC driver to alloc platform msi irq.
> - Fixed manivannan's comments.
>
> Frank Li (5):
> PCI: endpoint: Add RC-to-EP doorbell support using platform MSI
> controller
> PCI: dwc: add doorbell support by use MSI controller
> PCI: endpoint: pci-epf-test: add doorbell test
> misc: pci_endpoint_test: Add doorbell test case
> tools: PCI: Add 'B' option for test doorbell
>
> drivers/misc/pci_endpoint_test.c | 48 +++++
> .../pci/controller/dwc/pcie-designware-ep.c | 2 +
> drivers/pci/endpoint/functions/pci-epf-test.c | 59 +++++-
> drivers/pci/endpoint/pci-epc-core.c | 192 ++++++++++++++++++
> drivers/pci/endpoint/pci-epf-core.c | 44 ++++
> include/linux/pci-epc.h | 6 +
> include/linux/pci-epf.h | 7 +
> include/uapi/linux/pcitest.h | 1 +
> tools/pci/pcitest.c | 16 +-
> 9 files changed, 373 insertions(+), 2 deletions(-)
>
> --
> 2.34.1
>

Hello Frank,

Thank you for your work on this.
This series is very interesting.

As you probably know, IMS support was ripped out of the kernel a few
months ago:
b966b1102871 ("Revert "PCI/MSI: Provide IMS (Interrupt Message Store) support"")

So this series seems as relevant as ever.

Are you considering continuing work on this series any time soon?


Kind regards,
Niklas