On Thu, Oct 03, 2024 at 10:45:28AM +0530, Manivannan Sadhasivam wrote:

On Mon, Sep 30, 2024 at 03:42:20PM -0400, Frank Li wrote:

quoted

Some system's IOMMU stream(master) ID bits(such as 6bits) less than
pci_device_id (16bit). It needs add hardware configuration to enable
pci_device_id to stream ID convert.

https://lore.kernel.org/imx/20240622173849.GA1432357@bhelgaas/ (local)
This ways use pcie bus notifier (like apple pci controller), when new PCIe
device added, bus notifier will call register specific callback to handle
look up table (LUT) configuration.

https://lore.kernel.org/imx/20240429150842.GC1709920-robh@kernel.org/ (local)
which parse dt's 'msi-map' and 'iommu-map' property to static config LUT
table (qcom use this way). This way is rejected by DT maintainer Rob.

What is the issue in doing this during the probe() stage? It looks like you are
working with the static info in the devicetree, which is already available
during the controller probe().

There are problems.
One: It is not good to manually parser this property in pci host bridge
drivers.

Two: of_map default is bypass map. For example: if in dts only 2 sid, 0xA
and 0xB. If try to enable 3rd function RID(103), there are no error report.
of_map will return RID 103 as stream ID.  DMA will write to wrong
possition possibly.

https://elixir.bootlin.com/linux/v6.12-rc1/source/drivers/of/base.c#L2070

Three: LUT resource is limited, if DT provide 16 entry, but LUT have only 8
items, if more device enable, not LUT avaible and can't return error. of
course, it may fix dts, but It'd better that driver can handle error
properly when meet wrong dtb file.

quoted

Above ways can resolve LUT take or stream id out of usage the problem. If
there are not enough stream id resource, not error return, EP hardware
still issue DMA to do transfer, which may transfer to wrong possition.

Add enable(disable)_device() hook for bridge can return error when not
enough resource, and PCI device can't enabled.

{enable/disable}_device() doesn't convey the fact you are mapping BDF to SID in
the hardware. Maybe something like, {map/unmap}_bdf2sid() or similar would make
sense.

It is called in PCI common code do_pci_enable_device(), hook functin name
should be similar with caller. {map/unmap}_bdf2sid() is just implementation
in dwc.

stream id is only ARM platform concept.

May other host bridge do difference thing at enable/disable_device().

So I am still perfer use {enable/disable}_device().


Frank

- Mani

quoted

Basicallly this version can match Bjorn's requirement:
1: simple, because it is rare that there are no LUT resource.
2: EP driver probe failure when no LUT, but lspci can see such device.

[    2.164415] nvme nvme0: pci function 0000:01:00.0
[    2.169142] pci 0000:00:00.0: Error enabling bridge (-1), continuing
[    2.175654] nvme 0000:01:00.0: probe with driver nvme failed with error -12

quoted

lspci

0000:00:00.0 PCI bridge: Philips Semiconductors Device 0000
0000:01:00.0 Non-Volatile memory controller: Micron Technology Inc 2100AI NVMe SSD [Nitro] (rev 03)

To: Bjorn Helgaas <bhelgaas@google.com>
To: Richard Zhu <hongxing.zhu@nxp.com>
To: Lucas Stach <l.stach@pengutronix.de>
To: Lorenzo Pieralisi <lpieralisi@kernel.org>
To: Krzysztof Wilczyński <redacted>
To: Manivannan Sadhasivam <redacted>
To: Rob Herring <robh@kernel.org>
To: Shawn Guo <shawnguo@kernel.org>
To: Sascha Hauer <s.hauer@pengutronix.de>
To: Pengutronix Kernel Team <kernel@pengutronix.de>
To: Fabio Estevam <festevam@gmail.com>
Cc: linux-pci@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: imx@lists.linux.dev
Cc: Frank.li@nxp.com \
Cc: alyssa@rosenzweig.io \
Cc: bpf@vger.kernel.org \
Cc: broonie@kernel.org \
Cc: jgg@ziepe.ca \
Cc: joro@8bytes.org \
Cc: l.stach@pengutronix.de \
Cc: lgirdwood@gmail.com \
Cc: maz@kernel.org \
Cc: p.zabel@pengutronix.de \
Cc: robin.murphy@arm.com \
Cc: will@kernel.org \

Signed-off-by: Frank Li <Frank.Li@nxp.com>
---
Changes in v2:
- see each patch
- Link to v1: https://lore.kernel.org/r/20240926-imx95_lut-v1-0-d0c62087dbab@nxp.com (local)

---
Frank Li (2):
      PCI: Add enable_device() and disable_device() callbacks for bridges
      PCI: imx6: Add IOMMU and ITS MSI support for i.MX95

 drivers/pci/controller/dwc/pci-imx6.c | 133 +++++++++++++++++++++++++++++++++-
 drivers/pci/pci.c                     |  14 ++++
 include/linux/pci.h                   |   2 +
 3 files changed, 148 insertions(+), 1 deletion(-)
---
base-commit: 2849622e7b01d5aea1b060ba3955054798c1e0bb
change-id: 20240926-imx95_lut-1c68222e0944

Best regards,
---
Frank Li [off-list ref]

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