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Date:   Thu, 05 Nov 2020 09:20:11 +0000
From:   Marc Zyngier <maz@kernel.org>
To:     Thomas Gleixner <tglx@linutronix.de>
Cc:     Frank Wunderlich <frank-w@public-files.de>,
        Ryder Lee <ryder.lee@mediatek.com>,
        linux-mediatek@lists.infradead.org,
        Frank Wunderlich <linux@fw-web.de>,
        linux-kernel@vger.kernel.org,
        Matthias Brugger <matthias.bgg@gmail.com>,
        linux-pci@vger.kernel.org, Bjorn Helgaas <bhelgaas@google.com>
Subject: Re: Aw: Re:  Re: [PATCH] pci: mediatek: fix warning in msi.h
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On 2020-11-04 23:14, Thomas Gleixner wrote:

[...]

> TBH, that's butt ugly. So after staring long enough into the PCI code I
> came up with a way to transport that information to the probe code.
> 
> That allows a particular device to say 'I can't do MSI' and at the same
> time keeps the warning machinery intact which tells us that a 
> particular
> host controller driver is broken.
> 
> Uncompiled and untested as usual :)
> 
> Thanks,
> 
>         tglx
> ---
>  drivers/pci/controller/pcie-mediatek.c |    4 ++++
>  drivers/pci/probe.c                    |    3 +++
>  include/linux/pci.h                    |    1 +
>  3 files changed, 8 insertions(+)
> 
> --- a/drivers/pci/controller/pcie-mediatek.c
> +++ b/drivers/pci/controller/pcie-mediatek.c
> @@ -143,6 +143,7 @@ struct mtk_pcie_port;
>   * struct mtk_pcie_soc - differentiate between host generations
>   * @need_fix_class_id: whether this host's class ID needed to be fixed 
> or not
>   * @need_fix_device_id: whether this host's device ID needed to be 
> fixed or not
> + * @no_msi: Bridge has no MSI support
>   * @device_id: device ID which this host need to be fixed
>   * @ops: pointer to configuration access functions
>   * @startup: pointer to controller setting functions
> @@ -151,6 +152,7 @@ struct mtk_pcie_port;
>  struct mtk_pcie_soc {
>  	bool need_fix_class_id;
>  	bool need_fix_device_id;
> +	bool no_msi;
>  	unsigned int device_id;
>  	struct pci_ops *ops;
>  	int (*startup)(struct mtk_pcie_port *port);
> @@ -1084,6 +1086,7 @@ static int mtk_pcie_probe(struct platfor
> 
>  	host->ops = pcie->soc->ops;
>  	host->sysdata = pcie;
> +	host->no_msi = pcie->soc->no_msi;
> 
>  	err = pci_host_probe(host);
>  	if (err)
> @@ -1173,6 +1176,7 @@ static const struct dev_pm_ops mtk_pcie_
>  };
> 
>  static const struct mtk_pcie_soc mtk_pcie_soc_v1 = {
> +	.no_msi = true,
>  	.ops = &mtk_pcie_ops,
>  	.startup = mtk_pcie_startup_port,
>  };
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -889,6 +889,9 @@ static int pci_register_host_bridge(stru
>  	if (!bus)
>  		return -ENOMEM;
> 
> +	if (bridge->no_msi)
> +		bus->bus_flags |= PCI_BUS_FLAGS_NO_MSI;
> +
>  	bridge->bus = bus;
> 
>  	/* Temporarily move resources off the list */
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -545,6 +545,7 @@ struct pci_host_bridge {
>  	unsigned int	native_dpc:1;		/* OS may use PCIe DPC */
>  	unsigned int	preserve_config:1;	/* Preserve FW resource setup */
>  	unsigned int	size_windows:1;		/* Enable root bus sizing */
> +	unsigned int	no_msi:1;		/* Bridge has no MSI support */
> 
>  	/* Resource alignment requirements */
>  	resource_size_t (*align_resource)(struct pci_dev *dev,

If that's the direction of travel, we also need something like this
for configuration where the host bridge relies on an external MSI block
that uses MSI domains (boot-tested in a GICv3 guest).

         M.

diff --git a/drivers/pci/controller/pci-host-common.c 
b/drivers/pci/controller/pci-host-common.c
index 6ce34a1deecb..603f6fbbe68a 100644
--- a/drivers/pci/controller/pci-host-common.c
+++ b/drivers/pci/controller/pci-host-common.c
@@ -77,6 +77,7 @@ int pci_host_common_probe(struct platform_device 
*pdev)

  	bridge->sysdata = cfg;
  	bridge->ops = (struct pci_ops *)&ops->pci_ops;
+	bridge->msi_domain = true;

  	platform_set_drvdata(pdev, bridge);

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 16fb150fbb8d..f421b2869bca 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -889,9 +889,6 @@ static int pci_register_host_bridge(struct 
pci_host_bridge *bridge)
  	if (!bus)
  		return -ENOMEM;

-	if (bridge->no_msi)
-		bus->bus_flags |= PCI_BUS_FLAGS_NO_MSI;
-
  	bridge->bus = bus;

  	/* Temporarily move resources off the list */
@@ -928,6 +925,9 @@ static int pci_register_host_bridge(struct 
pci_host_bridge *bridge)
  	device_enable_async_suspend(bus->bridge);
  	pci_set_bus_of_node(bus);
  	pci_set_bus_msi_domain(bus);
+	if (bridge->no_msi ||
+	    (bridge->msi_domain && !bus->dev.msi_domain))
+		bus->bus_flags |= PCI_BUS_FLAGS_NO_MSI;

  	if (!parent)
  		set_dev_node(bus->bridge, pcibus_to_node(bus));
diff --git a/include/linux/pci.h b/include/linux/pci.h
index c2a0c1d471d6..81f72fd46e06 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -546,6 +546,7 @@ struct pci_host_bridge {
  	unsigned int	preserve_config:1;	/* Preserve FW resource setup */
  	unsigned int	size_windows:1;		/* Enable root bus sizing */
  	unsigned int	no_msi:1;		/* Bridge has no MSI support */
+	unsigned int	msi_domain:1;		/* Bridge wants MSI domain */

  	/* Resource alignment requirements */
  	resource_size_t (*align_resource)(struct pci_dev *dev,

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