Subject: Re: [PATCH v2 04/11] ACPI/IORT: Check ATS capability in root complex node

From: Bjorn Helgaas <[email-masked]>
Date: Thu, 12 Mar 2020 15:58:58 -0500

On Wed, Mar 11, 2020 at 01:44:59PM +0100, Jean-Philippe Brucker wrote:
> When initializing a PCI root bridge, copy its "ATS supported" attribute
> into the root bridge.
> 
> Acked-by: Hanjun Guo <[email-masked]>
> Signed-off-by: Jean-Philippe Brucker <[email-masked]>
> ---
>  drivers/acpi/arm64/iort.c | 27 +++++++++++++++++++++++++++
>  drivers/acpi/pci_root.c   |  3 +++
>  include/linux/acpi_iort.h |  8 ++++++++
>  3 files changed, 38 insertions(+)
> 
> diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
> index ed3d2d1a7ae9..d99d7f5b51e1 100644
> --- a/drivers/acpi/arm64/iort.c
> +++ b/drivers/acpi/arm64/iort.c
> @@ -1633,6 +1633,33 @@ static void __init iort_enable_acs(struct acpi_iort_node *iort_node)
>  		}
>  	}
>  }
> +
> +static acpi_status iort_match_host_bridge_callback(struct acpi_iort_node *node,
> +						   void *context)
> +{
> +	struct acpi_iort_root_complex *pci_rc;
> +	struct pci_host_bridge *host_bridge = context;
> +
> +	pci_rc = (struct acpi_iort_root_complex *)node->node_data;
> +
> +	return pci_domain_nr(host_bridge->bus) == pci_rc->pci_segment_number ?
> +		AE_OK : AE_NOT_FOUND;
> +}
> +
> +void iort_pci_host_bridge_setup(struct pci_host_bridge *host_bridge)
> +{
> +	struct acpi_iort_node *node;
> +	struct acpi_iort_root_complex *pci_rc;
> +
> +	node = iort_scan_node(ACPI_IORT_NODE_PCI_ROOT_COMPLEX,
> +			      iort_match_host_bridge_callback, host_bridge);
> +	if (!node)
> +		return;
> +
> +	pci_rc = (struct acpi_iort_root_complex *)node->node_data;
> +	host_bridge->ats_supported = !!(pci_rc->ats_attribute &
> +					ACPI_IORT_ATS_SUPPORTED);
> +}
>  #else
>  static inline void iort_enable_acs(struct acpi_iort_node *iort_node) { }
>  #endif
> diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
> index d1e666ef3fcc..eb2fb8f17c0b 100644
> --- a/drivers/acpi/pci_root.c
> +++ b/drivers/acpi/pci_root.c
> @@ -6,6 +6,7 @@
>   *  Copyright (C) 2001, 2002 Paul Diefenbaugh <[email-masked]>
>   */
>  
> +#include <linux/acpi_iort.h>
>  #include <linux/kernel.h>
>  #include <linux/module.h>
>  #include <linux/init.h>
> @@ -917,6 +918,8 @@ struct pci_bus *acpi_pci_root_create(struct acpi_pci_root *root,
>  	if (!(root->osc_control_set & OSC_PCI_EXPRESS_LTR_CONTROL))
>  		host_bridge->native_ltr = 0;
>  
> +	iort_pci_host_bridge_setup(host_bridge);

Similar comment as on the OF side.

You mentioned at [1] that "it's important that we only enable ATS if
the host bridge supports it".  That should be captured in a commit log
and comment somewhere here.

That suggests to me that we should not set

  bridge->ats_supported = 1;

by default in pci_init_host_bridge(), but rather leave it zero as it
is by default, and then do things like:

  if (iort_pci_host_bridge_ats_supported(bridge))
    bridge->ats_supported = 1;

  if (of_pci_host_bridge_ats_supported(bridge))
    bridge->ats_supported = 1;

I don't know what you do about IVRS and DMAR, which don't appear in
this series except in the comment.

[1] https://lore.kernel.org/r/[email-masked]

>  	/*
>  	 * Evaluate the "PCI Boot Configuration" _DSM Function.  If it
>  	 * exists and returns 0, we must preserve any PCI resource
> diff --git a/include/linux/acpi_iort.h b/include/linux/acpi_iort.h
> index 8e7e2ec37f1b..7b06871cc3aa 100644
> --- a/include/linux/acpi_iort.h
> +++ b/include/linux/acpi_iort.h
> @@ -10,6 +10,7 @@
>  #include <linux/acpi.h>
>  #include <linux/fwnode.h>
>  #include <linux/irqdomain.h>
> +#include <linux/pci.h>
>  
>  #define IORT_IRQ_MASK(irq)		(irq & 0xffffffffULL)
>  #define IORT_IRQ_TRIGGER_MASK(irq)	((irq >> 32) & 0xffffffffULL)
> @@ -55,4 +56,11 @@ int iort_iommu_msi_get_resv_regions(struct device *dev, struct list_head *head)
>  { return 0; }
>  #endif
>  
> +#if defined(CONFIG_ACPI_IORT) && defined(CONFIG_PCI)
> +void iort_pci_host_bridge_setup(struct pci_host_bridge *host_bridge);
> +#else
> +static inline
> +void iort_pci_host_bridge_setup(struct pci_host_bridge *host_bridge) { }
> +#endif
> +
>  #endif /* __ACPI_IORT_H__ */
> -- 
> 2.25.1
> 

_______________________________________________
linux-arm-kernel mailing list
[email-masked]
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel