linux-kernel - Re: [PATCH v2 0/2] PCI: add enabe(disable)

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Message-ID: <20241003051528.qrp2z7kvzgvymgjb@thinkpad>
Date: Thu, 3 Oct 2024 10:45:28 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Frank Li <Frank.Li@....com>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>, Richard Zhu <hongxing.zhu@....com>,
	Lucas Stach <l.stach@...gutronix.de>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Rob Herring <robh@...nel.org>, Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	imx@...ts.linux.dev, alyssa@...enzweig.io, bpf@...r.kernel.org,
	broonie@...nel.org, jgg@...pe.ca, joro@...tes.org,
	lgirdwood@...il.com, maz@...nel.org, p.zabel@...gutronix.de,
	robin.murphy@....com, will@...nel.org
Subject: Re: [PATCH v2 0/2] PCI: add enabe(disable)_device() hook for bridge

On Mon, Sep 30, 2024 at 03:42:20PM -0400, Frank Li wrote:
> 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/
> 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/
> 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().

> 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.

- Mani

> 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
> 
> > 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@...gle.com>
> To: Richard Zhu <hongxing.zhu@....com>
> To: Lucas Stach <l.stach@...gutronix.de>
> To: Lorenzo Pieralisi <lpieralisi@...nel.org>
> To: Krzysztof Wilczyński <kw@...ux.com>
> To: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> To: Rob Herring <robh@...nel.org>
> To: Shawn Guo <shawnguo@...nel.org>
> To: Sascha Hauer <s.hauer@...gutronix.de>
> To: Pengutronix Kernel Team <kernel@...gutronix.de>
> To: Fabio Estevam <festevam@...il.com>
> Cc: linux-pci@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> Cc: linux-arm-kernel@...ts.infradead.org
> Cc: imx@...ts.linux.dev
> Cc: Frank.li@....com \
> Cc: alyssa@...enzweig.io \
> Cc: bpf@...r.kernel.org \
> Cc: broonie@...nel.org \
> Cc: jgg@...pe.ca \
> Cc: joro@...tes.org \
> Cc: l.stach@...gutronix.de \
> Cc: lgirdwood@...il.com \
> Cc: maz@...nel.org \
> Cc: p.zabel@...gutronix.de \
> Cc: robin.murphy@....com \
> Cc: will@...nel.org \
> 
> Signed-off-by: Frank Li <Frank.Li@....com>
> ---
> Changes in v2:
> - see each patch
> - Link to v1: https://lore.kernel.org/r/20240926-imx95_lut-v1-0-d0c62087dbab@nxp.com
> 
> ---
> 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 <Frank.Li@....com>
> 
> 

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