Re: [Xen-devel] [PATCH v1 04/47] pci: add pci_ioremap_wc_bar()

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Fri, Mar 20, 2015 at 04:17:54PM -0700, Luis R. Rodriguez wrote:
> From: "Luis R. Rodriguez" <mcgrof@xxxxxxxx>
> 
> This lets drivers take advanate of PAT when available. This

s/advanate/advantage/
> should help with the transition of converting video drivers over
> to ioremap_wc() to help with the goal of eventually using
> _PAGE_CACHE_UC over _PAGE_CACHE_UC_MINUS on x86 on
> ioremap_nocache() (de33c442e)

Please mention the title of the patch too:

"x86 PAT: fix performance drop for glx, use UC minus for ioremap(), 
ioremap_nocache() and pci_mmap_page_range()"
> 
> Cc: Suresh Siddha <suresh.b.siddha@xxxxxxxxx>
> Cc: Venkatesh Pallipadi <venkatesh.pallipadi@xxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Juergen Gross <jgross@xxxxxxxx>
> Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
> Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
> Cc: Dave Airlie <airlied@xxxxxxxxxx>
> Cc: Antonino Daplas <adaplas@xxxxxxxxx>
> Cc: Jean-Christophe Plagniol-Villard <plagnioj@xxxxxxxxxxxx>
> Cc: Tomi Valkeinen <tomi.valkeinen@xxxxxx>
> Cc: linux-fbdev@xxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Signed-off-by: Luis R. Rodriguez <mcgrof@xxxxxxxx>
> ---
>  drivers/pci/pci.c   | 14 ++++++++++++++
>  include/linux/pci.h |  1 +
>  2 files changed, 15 insertions(+)
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 81f06e8..6afd507 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -137,6 +137,20 @@ void __iomem *pci_ioremap_bar(struct pci_dev *pdev, int 
> bar)
>                                    pci_resource_len(pdev, bar));
>  }
>  EXPORT_SYMBOL_GPL(pci_ioremap_bar);
> +
> +void __iomem *pci_ioremap_wc_bar(struct pci_dev *pdev, int bar)
> +{
> +     /*
> +      * Make sure the BAR is actually a memory resource, not an IO resource
> +      */
> +     if (!(pci_resource_flags(pdev, bar) & IORESOURCE_MEM)) {
> +             WARN_ON(1);

Would it be better to use dev_warn ? That way you can see which BDF it is?

Thought WARN will give a nice stack-trace that should easily point to the
driver so perhaps not.. Either way - up to you.

> +             return NULL;
> +     }
> +     return ioremap_wc(pci_resource_start(pdev, bar),
> +                       pci_resource_len(pdev, bar));
> +}
> +EXPORT_SYMBOL_GPL(pci_ioremap_wc_bar);
>  #endif
>  
>  #define PCI_FIND_CAP_TTL     48
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 211e9da..c235b09 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -1667,6 +1667,7 @@ static inline void pci_mmcfg_late_init(void) { }
>  int pci_ext_cfg_avail(void);
>  
>  void __iomem *pci_ioremap_bar(struct pci_dev *pdev, int bar);
> +void __iomem *pci_ioremap_wc_bar(struct pci_dev *pdev, int bar);
>  
>  #ifdef CONFIG_PCI_IOV
>  int pci_enable_sriov(struct pci_dev *dev, int nr_virtfn);
> -- 
> 2.3.2.209.gd67f9d5.dirty
> 
> 
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